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diff --git a/Unix/info/configure.info b/Unix/info/configure.info new file mode 100644 index 0000000..59c5038 --- /dev/null +++ b/Unix/info/configure.info @@ -0,0 +1,2773 @@ +This is configure.info, produced by makeinfo version 4.13 from +../../newlib-1.15.0/etc/configure.texi. + +INFO-DIR-SECTION GNU admin +START-INFO-DIR-ENTRY +* configure: (configure). The GNU configure and build system +END-INFO-DIR-ENTRY + + This file documents the GNU configure and build system. + + Copyright (C) 1998 Cygnus Solutions. + + Permission is granted to make and distribute verbatim copies of this +manual provided the copyright notice and this permission notice are +preserved on all copies. + + Permission is granted to copy and distribute modified versions of +this manual under the conditions for verbatim copying, provided that +the entire resulting derived work is distributed under the terms of a +permission notice identical to this one. + + Permission is granted to copy and distribute translations of this +manual into another language, under the above conditions for modified +versions, except that this permission notice may be stated in a +translation approved by the Foundation. + + +File: configure.info, Node: Top, Next: Introduction, Up: (dir) + +GNU configure and build system +****************************** + +The GNU configure and build system. + +* Menu: + +* Introduction:: Introduction. +* Getting Started:: Getting Started. +* Files:: Files. +* Configuration Names:: Configuration Names. +* Cross Compilation Tools:: Cross Compilation Tools. +* Canadian Cross:: Canadian Cross. +* Cygnus Configure:: Cygnus Configure. +* Multilibs:: Multilibs. +* FAQ:: Frequently Asked Questions. +* Index:: Index. + + +File: configure.info, Node: Introduction, Next: Getting Started, Prev: Top, Up: Top + +1 Introduction +************** + +This document describes the GNU configure and build systems. It +describes how autoconf, automake, libtool, and make fit together. It +also includes a discussion of the older Cygnus configure system. + + This document does not describe in detail how to use each of the +tools; see the respective manuals for that. Instead, it describes +which files the developer must write, which files are machine generated +and how they are generated, and where certain common problems should be +addressed. + + This document draws on several sources, including the autoconf +manual by David MacKenzie (*note autoconf overview: (autoconf)Top.), +the automake manual by David MacKenzie and Tom Tromey (*note automake +overview: (automake)Top.), the libtool manual by Gordon Matzigkeit +(*note libtool overview: (libtool)Top.), and the Cygnus configure +manual by K. Richard Pixley. + +* Menu: + +* Goals:: Goals. +* Tools:: The tools. +* History:: History. +* Building:: Building. + + +File: configure.info, Node: Goals, Next: Tools, Up: Introduction + +1.1 Goals +========= + +The GNU configure and build system has two main goals. + + The first is to simplify the development of portable programs. The +system permits the developer to concentrate on writing the program, +simplifying many details of portability across Unix and even Windows +systems, and permitting the developer to describe how to build the +program using simple rules rather than complex Makefiles. + + The second is to simplify the building of programs distributed as +source code. All programs are built using a simple, standardized, two +step process. The program builder need not install any special tools in +order to build the program. + + +File: configure.info, Node: Tools, Next: History, Prev: Goals, Up: Introduction + +1.2 Tools +========= + +The GNU configure and build system is comprised of several different +tools. Program developers must build and install all of these tools. + + People who just want to build programs from distributed sources +normally do not need any special tools beyond a Unix shell, a make +program, and a C compiler. + +autoconf + provides a general portability framework, based on testing the + features of the host system at build time. + +automake + a system for describing how to build a program, permitting the + developer to write a simplified `Makefile'. + +libtool + a standardized approach to building shared libraries. + +gettext + provides a framework for translation of text messages into other + languages; not really discussed in this document. + +m4 + autoconf requires the GNU version of m4; the standard Unix m4 does + not suffice. + +perl + automake requires perl. + + +File: configure.info, Node: History, Next: Building, Prev: Tools, Up: Introduction + +1.3 History +=========== + +This is a very brief and probably inaccurate history. + + As the number of Unix variants increased during the 1980s, it became +harder to write programs which could run on all variants. While it was +often possible to use `#ifdef' to identify particular systems, +developers frequently did not have access to every system, and the +characteristics of some systems changed from version to version. + + By 1992, at least three different approaches had been developed: + * The Metaconfig program, by Larry Wall, Harlan Stenn, and Raphael + Manfredi. + + * The Cygnus configure script, by K. Richard Pixley, and the gcc + configure script, by Richard Stallman. These use essentially the + same approach, and the developers communicated regularly. + + * The autoconf program, by David MacKenzie. + + The Metaconfig program is still used for Perl and a few other +programs. It is part of the Dist package. I do not know if it is +being developed. + + In 1994, David MacKenzie and others modified autoconf to incorporate +all the features of Cygnus configure. Since then, there has been a +slow but steady conversion of GNU programs from Cygnus configure to +autoconf. gcc has been converted, eliminating the gcc configure script. + + GNU autoconf was regularly maintained until late 1996. As of this +writing in June, 1998, it has no public maintainer. + + Most programs are built using the make program, which requires the +developer to write Makefiles describing how to build the programs. +Since most programs are built in pretty much the same way, this led to a +lot of duplication. + + The X Window system is built using the imake tool, which uses a +database of rules to eliminate the duplication. However, building a +tool which was developed using imake requires that the builder have +imake installed, violating one of the goals of the GNU system. + + The new BSD make provides a standard library of Makefile fragments, +which permits developers to write very simple Makefiles. However, this +requires that the builder install the new BSD make program. + + In 1994, David MacKenzie wrote the first version of automake, which +permitted writing a simple build description which was converted into a +Makefile which could be used by the standard make program. In 1995, Tom +Tromey completely rewrote automake in Perl, and he continues to enhance +it. + + Various free packages built libraries, and by around 1995 several +included support to build shared libraries on various platforms. +However, there was no consistent approach. In early 1996, Gordon +Matzigkeit began working on libtool, which provided a standardized +approach to building shared libraries. This was integrated into +automake from the start. + + The development of automake and libtool was driven by the GNITS +project, a group of GNU maintainers who designed standardized tools to +help meet the GNU coding standards. + + +File: configure.info, Node: Building, Prev: History, Up: Introduction + +1.4 Building +============ + +Most readers of this document should already know how to build a tool by +running `configure' and `make'. This section may serve as a quick +introduction or reminder. + + Building a tool is normally as simple as running `configure' +followed by `make'. You should normally run `configure' from an empty +directory, using some path to refer to the `configure' script in the +source directory. The directory in which you run `configure' is called +the "object directory". + + In order to use a object directory which is different from the source +directory, you must be using the GNU version of `make', which has the +required `VPATH' support. Despite this restriction, using a different +object directory is highly recommended: + * It keeps the files generated during the build from cluttering up + your sources. + + * It permits you to remove the built files by simply removing the + entire build directory. + + * It permits you to build from the same sources with several sets of + configure options simultaneously. + + If you don't have GNU `make', you will have to run `configure' in +the source directory. All GNU packages should support this; in +particular, GNU packages should not assume the presence of GNU `make'. + + After running `configure', you can build the tools by running `make'. + + To install the tools, run `make install'. Installing the tools will +copy the programs and any required support files to the "installation +directory". The location of the installation directory is controlled +by `configure' options, as described below. + + In the Cygnus tree at present, the info files are built and +installed as a separate step. To build them, run `make info'. To +install them, run `make install-info'. The equivalent html files are +also built and installed in a separate step. To build the html files, +run `make html'. To install the html files run `make install-html'. + + All `configure' scripts support a wide variety of options. The most +interesting ones are `--with' and `--enable' options which are +generally specific to particular tools. You can usually use the +`--help' option to get a list of interesting options for a particular +configure script. + + The only generic options you are likely to use are the `--prefix' +and `--exec-prefix' options. These options are used to specify the +installation directory. + + The directory named by the `--prefix' option will hold machine +independent files such as info files. + + The directory named by the `--exec-prefix' option, which is normally +a subdirectory of the `--prefix' directory, will hold machine dependent +files such as executables. + + The default for `--prefix' is `/usr/local'. The default for +`--exec-prefix' is the value used for `--prefix'. + + The convention used in Cygnus releases is to use a `--prefix' option +of `/usr/cygnus/RELEASE', where RELEASE is the name of the release, and +to use a `--exec-prefix' option of `/usr/cygnus/RELEASE/H-HOST', where +HOST is the configuration name of the host system (*note Configuration +Names::). + + Do not use either the source or the object directory as the +installation directory. That will just lead to confusion. + + +File: configure.info, Node: Getting Started, Next: Files, Prev: Introduction, Up: Top + +2 Getting Started +***************** + +To start using the GNU configure and build system with your software +package, you must write three files, and you must run some tools to +manually generate additional files. + +* Menu: + +* Write configure.in:: Write configure.in. +* Write Makefile.am:: Write Makefile.am. +* Write acconfig.h:: Write acconfig.h. +* Generate files:: Generate files. +* Getting Started Example:: Example. + + +File: configure.info, Node: Write configure.in, Next: Write Makefile.am, Up: Getting Started + +2.1 Write configure.in +====================== + +You must first write the file `configure.in'. This is an autoconf +input file, and the autoconf manual describes in detail what this file +should look like. + + You will write tests in your `configure.in' file to check for +conditions that may change from one system to another, such as the +presence of particular header files or functions. + + For example, not all systems support the `gettimeofday' function. +If you want to use the `gettimeofday' function when it is available, +and to use some other function when it is not, you would check for this +by putting `AC_CHECK_FUNCS(gettimeofday)' in `configure.in'. + + When the configure script is run at build time, this will arrange to +define the preprocessor macro `HAVE_GETTIMEOFDAY' to the value 1 if the +`gettimeofday' function is available, and to not define the macro at +all if the function is not available. Your code can then use `#ifdef' +to test whether it is safe to call `gettimeofday'. + + If you have an existing body of code, the `autoscan' program may +help identify potential portability problems, and hence configure tests +that you will want to use. *Note Invoking autoscan: (autoconf)Invoking +autoscan. + + Another handy tool for an existing body of code is `ifnames'. This +will show you all the preprocessor conditionals that the code already +uses. *Note Invoking ifnames: (autoconf)Invoking ifnames. + + Besides the portability tests which are specific to your particular +package, every `configure.in' file should contain the following macros. + +`AC_INIT' + This macro takes a single argument, which is the name of a file in + your package. For example, `AC_INIT(foo.c)'. + +`AC_PREREQ(VERSION)' + This macro is optional. It may be used to indicate the version of + `autoconf' that you are using. This will prevent users from + running an earlier version of `autoconf' and perhaps getting an + invalid `configure' script. For example, `AC_PREREQ(2.12)'. + +`AM_INIT_AUTOMAKE' + This macro takes two arguments: the name of the package, and a + version number. For example, `AM_INIT_AUTOMAKE(foo, 1.0)'. (This + macro is not needed if you are not using automake). + +`AM_CONFIG_HEADER' + This macro names the header file which will hold the preprocessor + macro definitions at run time. Normally this should be + `config.h'. Your sources would then use `#include "config.h"' to + include it. + + This macro may optionally name the input file for that header + file; by default, this is `config.h.in', but that file name works + poorly on DOS filesystems. Therefore, it is often better to name + it explicitly as `config.in'. + + This is what you should normally put in `configure.in': + AM_CONFIG_HEADER(config.h:config.in) + + (If you are not using automake, use `AC_CONFIG_HEADER' rather than + `AM_CONFIG_HEADER'). + +`AM_MAINTAINER_MODE' + This macro always appears in Cygnus configure scripts. Other + programs may or may not use it. + + If this macro is used, the `--enable-maintainer-mode' option is + required to enable automatic rebuilding of generated files used by + the configure system. This of course requires that developers be + aware of, and use, that option. + + If this macro is not used, then the generated files will always be + rebuilt automatically. This will cause problems if the wrong + versions of autoconf, automake, or others are in the builder's + `PATH'. + + (If you are not using automake, you do not need to use this macro). + +`AC_EXEEXT' + Either this macro or `AM_EXEEXT' always appears in Cygnus configure + files. Other programs may or may not use one of them. + + This macro looks for the executable suffix used on the host + system. On Unix systems, this is the empty string. On Windows + systems, this is `.exe'. This macro directs automake to use the + executable suffix as appropriate when creating programs. This + macro does not take any arguments. + + The `AC_EXEEXT' form is new, and is part of a Cygnus patch to + autoconf to support compiling with Visual C++. Older programs use + `AM_EXEEXT' instead. + + (Programs which do not use automake use neither `AC_EXEEXT' nor + `AM_EXEEXT'). + +`AC_PROG_CC' + If you are writing C code, you will normally want to use this + macro. It locates the C compiler to use. It does not take any + arguments. + + However, if this `configure.in' file is for a library which is to + be compiled by a cross compiler which may not fully work, then you + will not want to use `AC_PROG_CC'. Instead, you will want to use a + variant which does not call the macro `AC_PROG_CC_WORKS'. Examples + can be found in various `configure.in' files for libraries that are + compiled with cross compilers, such as libiberty or libgloss. + This is essentially a bug in autoconf, and there will probably be + a better workaround at some point. + +`AC_PROG_CXX' + If you are writing C++ code, you will want to use this macro. It + locates the C++ compiler to use. It does not take any arguments. + The same cross compiler comments apply as for `AC_PROG_CC'. + +`AM_PROG_LIBTOOL' + If you want to build libraries, and you want to permit them to be + shared, or you want to link against libraries which were built + using libtool, then you will need this macro. This macro is + required in order to use libtool. + + By default, this will cause all libraries to be built as shared + libraries. To prevent this-to change the default-use + `AM_DISABLE_SHARED' before `AM_PROG_LIBTOOL'. The configure + options `--enable-shared' and `--disable-shared' may be used to + override the default at build time. + +`AC_DEFINE(_GNU_SOURCE)' + GNU packages should normally include this line before any other + feature tests. This defines the macro `_GNU_SOURCE' when + compiling, which directs the libc header files to provide the + standard GNU system interfaces including all GNU extensions. If + this macro is not defined, certain GNU extensions may not be + available. + +`AC_OUTPUT' + This macro takes a list of file names which the configure process + should produce. This is normally a list of one or more `Makefile' + files in different directories. If your package lives entirely in + a single directory, you would use simply `AC_OUTPUT(Makefile)'. + If you also have, for example, a `lib' subdirectory, you would use + `AC_OUTPUT(Makefile lib/Makefile)'. + + If you want to use locally defined macros in your `configure.in' +file, then you will need to write a `acinclude.m4' file which defines +them (if not using automake, this file is called `aclocal.m4'). +Alternatively, you can put separate macros in an `m4' subdirectory, and +put `ACLOCAL_AMFLAGS = -I m4' in your `Makefile.am' file so that the +`aclocal' program will be able to find them. + + The different macro prefixes indicate which tool defines the macro. +Macros which start with `AC_' are part of autoconf. Macros which start +with `AM_' are provided by automake or libtool. + + +File: configure.info, Node: Write Makefile.am, Next: Write acconfig.h, Prev: Write configure.in, Up: Getting Started + +2.2 Write Makefile.am +===================== + +You must write the file `Makefile.am'. This is an automake input file, +and the automake manual describes in detail what this file should look +like. + + The automake commands in `Makefile.am' mostly look like variable +assignments in a `Makefile'. automake recognizes special variable +names, and automatically add make rules to the output as needed. + + There will be one `Makefile.am' file for each directory in your +package. For each directory with subdirectories, the `Makefile.am' +file should contain the line + SUBDIRS = DIR DIR ... + where each DIR is the name of a subdirectory. + + For each `Makefile.am', there should be a corresponding `Makefile' +in the `AC_OUTPUT' macro in `configure.in'. + + Every `Makefile.am' written at Cygnus should contain the line + AUTOMAKE_OPTIONS = cygnus + This puts automake into Cygnus mode. See the automake manual for +details. + + You may to include the version number of `automake' that you are +using on the `AUTOMAKE_OPTIONS' line. For example, + AUTOMAKE_OPTIONS = cygnus 1.3 + This will prevent users from running an earlier version of +`automake' and perhaps getting an invalid `Makefile.in'. + + If your package builds a program, then in the directory where that +program is built you will normally want a line like + bin_PROGRAMS = PROGRAM + where PROGRAM is the name of the program. You will then want a line +like + PROGRAM_SOURCES = FILE FILE ... + where each FILE is the name of a source file to link into the +program (e.g., `foo.c'). + + If your package builds a library, and you do not want the library to +ever be built as a shared library, then in the directory where that +library is built you will normally want a line like + lib_LIBRARIES = libNAME.a + where `libNAME.a' is the name of the library. You will then want a +line like + libNAME_a_SOURCES = FILE FILE ... + where each FILE is the name of a source file to add to the library. + + If your package builds a library, and you want to permit building the +library as a shared library, then in the directory where that library is +built you will normally want a line like + lib_LTLIBRARIES = libNAME.la + The use of `LTLIBRARIES', and the `.la' extension, indicate a +library to be built using libtool. As usual, you will then want a line +like + libNAME_la_SOURCES = FILE FILE ... + + The strings `bin' and `lib' that appear above in `bin_PROGRAMS' and +`lib_LIBRARIES' are not arbitrary. They refer to particular +directories, which may be set by the `--bindir' and `--libdir' options +to `configure'. If those options are not used, the default values are +based on the `--prefix' or `--exec-prefix' options to `configure'. It +is possible to use other names if the program or library should be +installed in some other directory. + + The `Makefile.am' file may also contain almost anything that may +appear in a normal `Makefile'. automake also supports many other +special variables, as well as conditionals. + + See the automake manual for more information. + + +File: configure.info, Node: Write acconfig.h, Next: Generate files, Prev: Write Makefile.am, Up: Getting Started + +2.3 Write acconfig.h +==================== + +If you are generating a portability header file, (i.e., you are using +`AM_CONFIG_HEADER' in `configure.in'), then you will have to write a +`acconfig.h' file. It will have to contain the following lines. + + /* Name of package. */ + #undef PACKAGE + + /* Version of package. */ + #undef VERSION + + This requirement is really a bug in the system, and the requirement +may be eliminated at some later date. + + The `acconfig.h' file will also similar comment and `#undef' lines +for any unusual macros in the `configure.in' file, including any macro +which appears in a `AC_DEFINE' macro. + + In particular, if you are writing a GNU package and therefore include +`AC_DEFINE(_GNU_SOURCE)' in `configure.in' as suggested above, you will +need lines like this in `acconfig.h': + /* Enable GNU extensions. */ + #undef _GNU_SOURCE + + Normally the `autoheader' program will inform you of any such +requirements by printing an error message when it is run. However, if +you do anything particular odd in your `configure.in' file, you will +have to make sure that the right entries appear in `acconfig.h', since +otherwise the results of the tests may not be available in the +`config.h' file which your code will use. + + (Thee `PACKAGE' and `VERSION' lines are not required if you are not +using automake, and in that case you may not need a `acconfig.h' file +at all). + + +File: configure.info, Node: Generate files, Next: Getting Started Example, Prev: Write acconfig.h, Up: Getting Started + +2.4 Generate files +================== + +Once you have written `configure.in', `Makefile.am', `acconfig.h', and +possibly `acinclude.m4', you must use autoconf and automake programs to +produce the first versions of the generated files. This is done by +executing the following sequence of commands. + + aclocal + autoconf + autoheader + automake + + The `aclocal' and `automake' commands are part of the automake +package, and the `autoconf' and `autoheader' commands are part of the +autoconf package. + + If you are using a `m4' subdirectory for your macros, you will need +to use the `-I m4' option when you run `aclocal'. + + If you are not using the Cygnus tree, use the `-a' option when +running `automake' command in order to copy the required support files +into your source directory. + + If you are using libtool, you must build and install the libtool +package with the same `--prefix' and `--exec-prefix' options as you +used with the autoconf and automake packages. You must do this before +running any of the above commands. If you are not using the Cygnus +tree, you will need to run the `libtoolize' program to copy the libtool +support files into your directory. + + Once you have managed to run these commands without getting any +errors, you should create a new empty directory, and run the `configure' +script which will have been created by `autoconf' with the +`--enable-maintainer-mode' option. This will give you a set of +Makefiles which will include rules to automatically rebuild all the +generated files. + + After doing that, whenever you have changed some of the input files +and want to regenerated the other files, go to your object directory +and run `make'. Doing this is more reliable than trying to rebuild the +files manually, because there are complex order dependencies and it is +easy to forget something. + + +File: configure.info, Node: Getting Started Example, Prev: Generate files, Up: Getting Started + +2.5 Example +=========== + +Let's consider a trivial example. + + Suppose we want to write a simple version of `touch'. Our program, +which we will call `poke', will take a single file name argument, and +use the `utime' system call to set the modification and access times of +the file to the current time. We want this program to be highly +portable. + + We'll first see what this looks like without using autoconf and +automake, and then see what it looks like with them. + +* Menu: + +* Getting Started Example 1:: First Try. +* Getting Started Example 2:: Second Try. +* Getting Started Example 3:: Third Try. +* Generate Files in Example:: Generate Files. + + +File: configure.info, Node: Getting Started Example 1, Next: Getting Started Example 2, Up: Getting Started Example + +2.5.1 First Try +--------------- + +Here is our first try at `poke.c'. Note that we've written it without +ANSI/ISO C prototypes, since we want it to be highly portable. + + #include <stdio.h> + #include <stdlib.h> + #include <sys/types.h> + #include <utime.h> + + int + main (argc, argv) + int argc; + char **argv; + { + if (argc != 2) + { + fprintf (stderr, "Usage: poke file\n"); + exit (1); + } + + if (utime (argv[1], NULL) < 0) + { + perror ("utime"); + exit (1); + } + + exit (0); + } + + We also write a simple `Makefile'. + + CC = gcc + CFLAGS = -g -O2 + + all: poke + + poke: poke.o + $(CC) -o poke $(CFLAGS) $(LDFLAGS) poke.o + + So far, so good. + + Unfortunately, there are a few problems. + + On older Unix systems derived from BSD 4.3, the `utime' system call +does not accept a second argument of `NULL'. On those systems, we need +to pass a pointer to `struct utimbuf' structure. Unfortunately, even +older systems don't define that structure; on those systems, we need to +pass an array of two `long' values. + + The header file `stdlib.h' was invented by ANSI C, and older systems +don't have a copy. We included it above to get a declaration of `exit'. + + We can find some of these portability problems by running +`autoscan', which will create a `configure.scan' file which we can use +as a prototype for our `configure.in' file. I won't show the output, +but it will notice the potential problems with `utime' and `stdlib.h'. + + In our `Makefile', we don't provide any way to install the program. +This doesn't matter much for such a simple example, but a real program +will need an `install' target. For that matter, we will also want a +`clean' target. + + +File: configure.info, Node: Getting Started Example 2, Next: Getting Started Example 3, Prev: Getting Started Example 1, Up: Getting Started Example + +2.5.2 Second Try +---------------- + +Here is our second try at this program. + + We modify `poke.c' to use preprocessor macros to control what +features are available. (I've cheated a bit by using the same macro +names which autoconf will use). + + #include <stdio.h> + + #ifdef STDC_HEADERS + #include <stdlib.h> + #endif + + #include <sys/types.h> + + #ifdef HAVE_UTIME_H + #include <utime.h> + #endif + + #ifndef HAVE_UTIME_NULL + + #include <time.h> + + #ifndef HAVE_STRUCT_UTIMBUF + + struct utimbuf + { + long actime; + long modtime; + }; + + #endif + + static int + utime_now (file) + char *file; + { + struct utimbuf now; + + now.actime = now.modtime = time (NULL); + return utime (file, &now); + } + + #define utime(f, p) utime_now (f) + + #endif /* HAVE_UTIME_NULL */ + + int + main (argc, argv) + int argc; + char **argv; + { + if (argc != 2) + { + fprintf (stderr, "Usage: poke file\n"); + exit (1); + } + + if (utime (argv[1], NULL) < 0) + { + perror ("utime"); + exit (1); + } + + exit (0); + } + + Here is the associated `Makefile'. We've added support for the +preprocessor flags we use. We've also added `install' and `clean' +targets. + + # Set this to your installation directory. + bindir = /usr/local/bin + + # Uncomment this if you have the standard ANSI/ISO C header files. + # STDC_HDRS = -DSTDC_HEADERS + + # Uncomment this if you have utime.h. + # UTIME_H = -DHAVE_UTIME_H + + # Uncomment this if utime (FILE, NULL) works on your system. + # UTIME_NULL = -DHAVE_UTIME_NULL + + # Uncomment this if struct utimbuf is defined in utime.h. + # UTIMBUF = -DHAVE_STRUCT_UTIMBUF + + CC = gcc + CFLAGS = -g -O2 + + ALL_CFLAGS = $(STDC_HDRS) $(UTIME_H) $(UTIME_NULL) $(UTIMBUF) $(CFLAGS) + + all: poke + + poke: poke.o + $(CC) -o poke $(ALL_CFLAGS) $(LDFLAGS) poke.o + + .c.o: + $(CC) -c $(ALL_CFLAGS) poke.c + + install: poke + cp poke $(bindir)/poke + + clean: + rm poke poke.o + + Some problems with this approach should be clear. + + Users who want to compile poke will have to know how `utime' works +on their systems, so that they can uncomment the `Makefile' correctly. + + The installation is done using `cp', but many systems have an +`install' program which may be used, and which supports optional +features such as stripping debugging information out of the installed +binary. + + The use of `Makefile' variables like `CC', `CFLAGS' and `LDFLAGS' +follows the requirements of the GNU standards. This is convenient for +all packages, since it reduces surprises for users. However, it is +easy to get the details wrong, and wind up with a slightly nonstandard +distribution. + + +File: configure.info, Node: Getting Started Example 3, Next: Generate Files in Example, Prev: Getting Started Example 2, Up: Getting Started Example + +2.5.3 Third Try +--------------- + +For our third try at this program, we will write a `configure.in' +script to discover the configuration features on the host system, rather +than requiring the user to edit the `Makefile'. We will also write a +`Makefile.am' rather than a `Makefile'. + + The only change to `poke.c' is to add a line at the start of the +file: + #include "config.h" + + The new `configure.in' file is as follows. + + AC_INIT(poke.c) + AM_INIT_AUTOMAKE(poke, 1.0) + AM_CONFIG_HEADER(config.h:config.in) + AC_PROG_CC + AC_HEADER_STDC + AC_CHECK_HEADERS(utime.h) + AC_EGREP_HEADER(utimbuf, utime.h, AC_DEFINE(HAVE_STRUCT_UTIMBUF)) + AC_FUNC_UTIME_NULL + AC_OUTPUT(Makefile) + + The first four macros in this file, and the last one, were described +above; see *note Write configure.in::. If we omit these macros, then +when we run `automake' we will get a reminder that we need them. + + The other macros are standard autoconf macros. + +`AC_HEADER_STDC' + Check for standard C headers. + +`AC_CHECK_HEADERS' + Check whether a particular header file exists. + +`AC_EGREP_HEADER' + Check for a particular string in a particular header file, in this + case checking for `utimbuf' in `utime.h'. + +`AC_FUNC_UTIME_NULL' + Check whether `utime' accepts a NULL second argument to set the + file change time to the current time. + + See the autoconf manual for a more complete description. + + The new `Makefile.am' file is as follows. Note how simple this is +compared to our earlier `Makefile'. + + bin_PROGRAMS = poke + + poke_SOURCES = poke.c + + This means that we should build a single program name `poke'. It +should be installed in the binary directory, which we called `bindir' +earlier. The program `poke' is built from the source file `poke.c'. + + We must also write a `acconfig.h' file. Besides `PACKAGE' and +`VERSION', which must be mentioned for all packages which use automake, +we must include `HAVE_STRUCT_UTIMBUF', since we mentioned it in an +`AC_DEFINE'. + + /* Name of package. */ + #undef PACKAGE + + /* Version of package. */ + #undef VERSION + + /* Whether utime.h defines struct utimbuf. */ + #undef HAVE_STRUCT_UTIMBUF + + +File: configure.info, Node: Generate Files in Example, Prev: Getting Started Example 3, Up: Getting Started Example + +2.5.4 Generate Files +-------------------- + +We must now generate the other files, using the following commands. + + aclocal + autoconf + autoheader + automake + + When we run `autoheader', it will remind us of any macros we forgot +to add to `acconfig.h'. + + When we run `automake', it will want to add some files to our +distribution. It will add them automatically if we use the +`--add-missing' option. + + By default, `automake' will run in GNU mode, which means that it +will want us to create certain additional files; as of this writing, it +will want `NEWS', `README', `AUTHORS', and `ChangeLog', all of which +are files which should appear in a standard GNU distribution. We can +either add those files, or run `automake' with the `--foreign' option. + + Running these tools will generate the following files, all of which +are described in the next chapter. + + * `aclocal.m4' + + * `configure' + + * `config.in' + + * `Makefile.in' + + * `stamp-h.in' + + +File: configure.info, Node: Files, Next: Configuration Names, Prev: Getting Started, Up: Top + +3 Files +******* + +As was seen in the previous chapter, the GNU configure and build system +uses a number of different files. The developer must write a few files. +The others are generated by various tools. + + The system is rather flexible, and can be used in many different +ways. In describing the files that it uses, I will describe the common +case, and mention some other cases that may arise. + +* Menu: + +* Developer Files:: Developer Files. +* Build Files:: Build Files. +* Support Files:: Support Files. + + +File: configure.info, Node: Developer Files, Next: Build Files, Up: Files + +3.1 Developer Files +=================== + +This section describes the files written or generated by the developer +of a package. + +* Menu: + +* Developer Files Picture:: Developer Files Picture. +* Written Developer Files:: Written Developer Files. +* Generated Developer Files:: Generated Developer Files. + + +File: configure.info, Node: Developer Files Picture, Next: Written Developer Files, Up: Developer Files + +3.1.1 Developer Files Picture +----------------------------- + +Here is a picture of the files which are written by the developer, the +generated files which would be included with a complete source +distribution, and the tools which create those files. The file names +are plain text and the tool names are enclosed by `*' characters (e.g., +`autoheader' is the name of a tool, not the name of a file). + + acconfig.h configure.in Makefile.am + | | | + | --------------+---------------------- | + | | | | | + v v | acinclude.m4 | | + *autoheader* | | v v + | | v --->*automake* + v |--->*aclocal* | | + config.in | | | v + | v | Makefile.in + | aclocal.m4--- + | | + v v + *autoconf* + | + v + configure + + +File: configure.info, Node: Written Developer Files, Next: Generated Developer Files, Prev: Developer Files Picture, Up: Developer Files + +3.1.2 Written Developer Files +----------------------------- + +The following files would be written by the developer. + +`configure.in' + This is the configuration script. This script contains + invocations of autoconf macros. It may also contain ordinary + shell script code. This file will contain feature tests for + portability issues. The last thing in the file will normally be + an `AC_OUTPUT' macro listing which files to create when the + builder runs the configure script. This file is always required + when using the GNU configure system. *Note Write configure.in::. + +`Makefile.am' + This is the automake input file. It describes how the code should + be built. It consists of definitions of automake variables. It + may also contain ordinary Makefile targets. This file is only + needed when using automake (newer tools normally use automake, but + there are still older tools which have not been converted, in + which the developer writes `Makefile.in' directly). *Note Write + Makefile.am::. + +`acconfig.h' + When the configure script creates a portability header file, by + using `AM_CONFIG_HEADER' (or, if not using automake, + `AC_CONFIG_HEADER'), this file is used to describe macros which are + not recognized by the `autoheader' command. This is normally a + fairly uninteresting file, consisting of a collection of `#undef' + lines with comments. Normally any call to `AC_DEFINE' in + `configure.in' will require a line in this file. *Note Write + acconfig.h::. + +`acinclude.m4' + This file is not always required. It defines local autoconf + macros. These macros may then be used in `configure.in'. If you + don't need any local autoconf macros, then you don't need this + file at all. In fact, in general, you never need local autoconf + macros, since you can put everything in `configure.in', but + sometimes a local macro is convenient. + + Newer tools may omit `acinclude.m4', and instead use a + subdirectory, typically named `m4', and define `ACLOCAL_AMFLAGS = + -I m4' in `Makefile.am' to force `aclocal' to look there for macro + definitions. The macro definitions are then placed in separate + files in that directory. + + The `acinclude.m4' file is only used when using automake; in older + tools, the developer writes `aclocal.m4' directly, if it is needed. + + +File: configure.info, Node: Generated Developer Files, Prev: Written Developer Files, Up: Developer Files + +3.1.3 Generated Developer Files +------------------------------- + +The following files would be generated by the developer. + + When using automake, these files are normally not generated manually +after the first time. Instead, the generated `Makefile' contains rules +to automatically rebuild the files as required. When +`AM_MAINTAINER_MODE' is used in `configure.in' (the normal case in +Cygnus code), the automatic rebuilding rules will only be defined if +you configure using the `--enable-maintainer-mode' option. + + When using automatic rebuilding, it is important to ensure that all +the various tools have been built and installed on your `PATH'. Using +automatic rebuilding is highly recommended, so much so that I'm not +going to explain what you have to do if you don't use it. + +`configure' + This is the configure script which will be run when building the + package. This is generated by `autoconf' from `configure.in' and + `aclocal.m4'. This is a shell script. + +`Makefile.in' + This is the file which the configure script will turn into the + `Makefile' at build time. This file is generated by `automake' + from `Makefile.am'. If you aren't using automake, you must write + this file yourself. This file is pretty much a normal `Makefile', + with some configure substitutions for certain variables. + +`aclocal.m4' + This file is created by the `aclocal' program, based on the + contents of `configure.in' and `acinclude.m4' (or, as noted in the + description of `acinclude.m4' above, on the contents of an `m4' + subdirectory). This file contains definitions of autoconf macros + which `autoconf' will use when generating the file `configure'. + These autoconf macros may be defined by you in `acinclude.m4' or + they may be defined by other packages such as automake, libtool or + gettext. If you aren't using automake, you will normally write + this file yourself; in that case, if `configure.in' uses only + standard autoconf macros, this file will not be needed at all. + +`config.in' + This file is created by `autoheader' based on `acconfig.h' and + `configure.in'. At build time, the configure script will define + some of the macros in it to create `config.h', which may then be + included by your program. This permits your C code to use + preprocessor conditionals to change its behaviour based on the + characteristics of the host system. This file may also be called + `config.h.in'. + +`stamp.h-in' + This rather uninteresting file, which I omitted from the picture, + is generated by `automake'. It always contains the string + `timestamp'. It is used as a timestamp file indicating whether + `config.in' is up to date. Using a timestamp file means that + `config.in' can be marked as up to date without actually changing + its modification time. This is useful since `config.in' depends + upon `configure.in', but it is easy to change `configure.in' in a + way which does not affect `config.in'. + + +File: configure.info, Node: Build Files, Next: Support Files, Prev: Developer Files, Up: Files + +3.2 Build Files +=============== + +This section describes the files which are created at configure and +build time. These are the files which somebody who builds the package +will see. + + Of course, the developer will also build the package. The +distinction between developer files and build files is not that the +developer does not see the build files, but that somebody who only +builds the package does not have to worry about the developer files. + +* Menu: + +* Build Files Picture:: Build Files Picture. +* Build Files Description:: Build Files Description. + + +File: configure.info, Node: Build Files Picture, Next: Build Files Description, Up: Build Files + +3.2.1 Build Files Picture +------------------------- + +Here is a picture of the files which will be created at build time. +`config.status' is both a created file and a shell script which is run +to create other files, and the picture attempts to show that. + + config.in *configure* Makefile.in + | | | + | v | + | config.status | + | | | + *config.status*<======+==========>*config.status* + | | + v v + config.h Makefile + + +File: configure.info, Node: Build Files Description, Prev: Build Files Picture, Up: Build Files + +3.2.2 Build Files Description +----------------------------- + +This is a description of the files which are created at build time. + +`config.status' + The first step in building a package is to run the `configure' + script. The `configure' script will create the file + `config.status', which is itself a shell script. When you first + run `configure', it will automatically run `config.status'. An + `Makefile' derived from an automake generated `Makefile.in' will + contain rules to automatically run `config.status' again when + necessary to recreate certain files if their inputs change. + +`Makefile' + This is the file which make will read to build the program. The + `config.status' script will transform `Makefile.in' into + `Makefile'. + +`config.h' + This file defines C preprocessor macros which C code can use to + adjust its behaviour on different systems. The `config.status' + script will transform `config.in' into `config.h'. + +`config.cache' + This file did not fit neatly into the picture, and I omitted it. + It is used by the `configure' script to cache results between + runs. This can be an important speedup. If you modify + `configure.in' in such a way that the results of old tests should + change (perhaps you have added a new library to `LDFLAGS'), then + you will have to remove `config.cache' to force the tests to be + rerun. + + The autoconf manual explains how to set up a site specific cache + file. This can speed up running `configure' scripts on your + system. + +`stamp.h' + This file, which I omitted from the picture, is similar to + `stamp-h.in'. It is used as a timestamp file indicating whether + `config.h' is up to date. This is useful since `config.h' depends + upon `config.status', but it is easy for `config.status' to change + in a way which does not affect `config.h'. + + +File: configure.info, Node: Support Files, Prev: Build Files, Up: Files + +3.3 Support Files +================= + +The GNU configure and build system requires several support files to be +included with your distribution. You do not normally need to concern +yourself with these. If you are using the Cygnus tree, most are already +present. Otherwise, they will be installed with your source by +`automake' (with the `--add-missing' option) and `libtoolize'. + + You don't have to put the support files in the top level directory. +You can put them in a subdirectory, and use the `AC_CONFIG_AUX_DIR' +macro in `configure.in' to tell `automake' and the `configure' script +where they are. + + In this section, I describe the support files, so that you can know +what they are and why they are there. + +`ABOUT-NLS' + Added by automake if you are using gettext. This is a + documentation file about the gettext project. + +`ansi2knr.c' + Used by an automake generated `Makefile' if you put `ansi2knr' in + `AUTOMAKE_OPTIONS' in `Makefile.am'. This permits compiling ANSI + C code with a K&R C compiler. + +`ansi2knr.1' + The man page which goes with `ansi2knr.c'. + +`config.guess' + A shell script which determines the configuration name for the + system on which it is run. + +`config.sub' + A shell script which canonicalizes a configuration name entered by + a user. + +`elisp-comp' + Used to compile Emacs LISP files. + +`install-sh' + A shell script which installs a program. This is used if the + configure script can not find an install binary. + +`ltconfig' + Used by libtool. This is a shell script which configures libtool + for the particular system on which it is used. + +`ltmain.sh' + Used by libtool. This is the actual libtool script which is used, + after it is configured by `ltconfig' to build a library. + +`mdate-sh' + A shell script used by an automake generated `Makefile' to pretty + print the modification time of a file. This is used to maintain + version numbers for texinfo files. + +`missing' + A shell script used if some tool is missing entirely. This is + used by an automake generated `Makefile' to avoid certain sorts of + timestamp problems. + +`mkinstalldirs' + A shell script which creates a directory, including all parent + directories. This is used by an automake generated `Makefile' + during installation. + +`texinfo.tex' + Required if you have any texinfo files. This is used when + converting Texinfo files into DVI using `texi2dvi' and TeX. + +`ylwrap' + A shell script used by an automake generated `Makefile' to run + programs like `bison', `yacc', `flex', and `lex'. These programs + default to producing output files with a fixed name, and the + `ylwrap' script runs them in a subdirectory to avoid file name + conflicts when using a parallel make program. + + +File: configure.info, Node: Configuration Names, Next: Cross Compilation Tools, Prev: Files, Up: Top + +4 Configuration Names +********************* + +The GNU configure system names all systems using a "configuration +name". All such names used to be triplets (they may now contain four +parts in certain cases), and the term "configuration triplet" is still +seen. + +* Menu: + +* Configuration Name Definition:: Configuration Name Definition. +* Using Configuration Names:: Using Configuration Names. + + +File: configure.info, Node: Configuration Name Definition, Next: Using Configuration Names, Up: Configuration Names + +4.1 Configuration Name Definition +================================= + +This is a string of the form CPU-MANUFACTURER-OPERATING_SYSTEM. In +some cases, this is extended to a four part form: +CPU-MANUFACTURER-KERNEL-OPERATING_SYSTEM. + + When using a configuration name in a configure option, it is normally +not necessary to specify an entire name. In particular, the +MANUFACTURER field is often omitted, leading to strings such as +`i386-linux' or `sparc-sunos'. The shell script `config.sub' will +translate these shortened strings into the canonical form. autoconf +will arrange for `config.sub' to be run automatically when it is needed. + + The fields of a configuration name are as follows: + +CPU + The type of processor. This is typically something like `i386' or + `sparc'. More specific variants are used as well, such as + `mipsel' to indicate a little endian MIPS processor. + +MANUFACTURER + A somewhat freeform field which indicates the manufacturer of the + system. This is often simply `unknown'. Other common strings are + `pc' for an IBM PC compatible system, or the name of a workstation + vendor, such as `sun'. + +OPERATING_SYSTEM + The name of the operating system which is run on the system. This + will be something like `solaris2.5' or `irix6.3'. There is no + particular restriction on the version number, and strings like + `aix4.1.4.0' are seen. For an embedded system, which has no + operating system, this field normally indicates the type of object + file format, such as `elf' or `coff'. + +KERNEL + This is used mainly for GNU/Linux. A typical GNU/Linux + configuration name is `i586-pc-linux-gnulibc1'. In this case the + kernel, `linux', is separated from the operating system, + `gnulibc1'. + + The shell script `config.guess' will normally print the correct +configuration name for the system on which it is run. It does by +running `uname' and by examining other characteristics of the system. + + Because `config.guess' can normally determine the configuration name +for a machine, it is normally only necessary to specify a configuration +name when building a cross-compiler or when building using a +cross-compiler. + + +File: configure.info, Node: Using Configuration Names, Prev: Configuration Name Definition, Up: Configuration Names + +4.2 Using Configuration Names +============================= + +A configure script will sometimes have to make a decision based on a +configuration name. You will need to do this if you have to compile +code differently based on something which can not be tested using a +standard autoconf feature test. + + It is normally better to test for particular features, rather than to +test for a particular system. This is because as Unix evolves, +different systems copy features from one another. Even if you need to +determine whether the feature is supported based on a configuration +name, you should define a macro which describes the feature, rather than +defining a macro which describes the particular system you are on. + + Testing for a particular system is normally done using a case +statement in `configure.in'. The case statement might look something +like the following, assuming that `host' is a shell variable holding a +canonical configuration name (which will be the case if `configure.in' +uses the `AC_CANONICAL_HOST' or `AC_CANONICAL_SYSTEM' macro). + + case "${host}" in + i[3-7]86-*-linux-gnu*) do something ;; + sparc*-sun-solaris2.[56789]*) do something ;; + sparc*-sun-solaris*) do something ;; + mips*-*-elf*) do something ;; + esac + + It is particularly important to use `*' after the operating system +field, in order to match the version number which will be generated by +`config.guess'. + + In most cases you must be careful to match a range of processor +types. For most processor families, a trailing `*' suffices, as in +`mips*' above. For the i386 family, something along the lines of +`i[3-7]86' suffices at present. For the m68k family, you will need +something like `m68*'. Of course, if you do not need to match on the +processor, it is simpler to just replace the entire field by a `*', as +in `*-*-irix*'. + + +File: configure.info, Node: Cross Compilation Tools, Next: Canadian Cross, Prev: Configuration Names, Up: Top + +5 Cross Compilation Tools +************************* + +The GNU configure and build system can be used to build "cross +compilation" tools. A cross compilation tool is a tool which runs on +one system and produces code which runs on another system. + +* Menu: + +* Cross Compilation Concepts:: Cross Compilation Concepts. +* Host and Target:: Host and Target. +* Using the Host Type:: Using the Host Type. +* Specifying the Target:: Specifying the Target. +* Using the Target Type:: Using the Target Type. +* Cross Tools in the Cygnus Tree:: Cross Tools in the Cygnus Tree + + +File: configure.info, Node: Cross Compilation Concepts, Next: Host and Target, Up: Cross Compilation Tools + +5.1 Cross Compilation Concepts +============================== + +A compiler which produces programs which run on a different system is a +cross compilation compiler, or simply a "cross compiler". Similarly, +we speak of cross assemblers, cross linkers, etc. + + In the normal case, a compiler produces code which runs on the same +system as the one on which the compiler runs. When it is necessary to +distinguish this case from the cross compilation case, such a compiler +is called a "native compiler". Similarly, we speak of native +assemblers, etc. + + Although the debugger is not strictly speaking a compilation tool, +it is nevertheless meaningful to speak of a cross debugger: a debugger +which is used to debug code which runs on another system. Everything +that is said below about configuring cross compilation tools applies to +the debugger as well. + + +File: configure.info, Node: Host and Target, Next: Using the Host Type, Prev: Cross Compilation Concepts, Up: Cross Compilation Tools + +5.2 Host and Target +=================== + +When building cross compilation tools, there are two different systems +involved: the system on which the tools will run, and the system for +which the tools generate code. + + The system on which the tools will run is called the "host" system. + + The system for which the tools generate code is called the "target" +system. + + For example, suppose you have a compiler which runs on a GNU/Linux +system and generates ELF programs for a MIPS embedded system. In this +case the GNU/Linux system is the host, and the MIPS ELF system is the +target. Such a compiler could be called a GNU/Linux cross MIPS ELF +compiler, or, equivalently, a `i386-linux-gnu' cross `mips-elf' +compiler. + + Naturally, most programs are not cross compilation tools. For those +programs, it does not make sense to speak of a target. It only makes +sense to speak of a target for tools like `gcc' or the `binutils' which +actually produce running code. For example, it does not make sense to +speak of the target of a tool like `bison' or `make'. + + Most cross compilation tools can also serve as native tools. For a +native compilation tool, it is still meaningful to speak of a target. +For a native tool, the target is the same as the host. For example, for +a GNU/Linux native compiler, the host is GNU/Linux, and the target is +also GNU/Linux. + + +File: configure.info, Node: Using the Host Type, Next: Specifying the Target, Prev: Host and Target, Up: Cross Compilation Tools + +5.3 Using the Host Type +======================= + +In almost all cases the host system is the system on which you run the +`configure' script, and on which you build the tools (for the case when +they differ, *note Canadian Cross::). + + If your configure script needs to know the configuration name of the +host system, and the package is not a cross compilation tool and +therefore does not have a target, put `AC_CANONICAL_HOST' in +`configure.in'. This macro will arrange to define a few shell +variables when the `configure' script is run. + +`host' + The canonical configuration name of the host. This will normally + be determined by running the `config.guess' shell script, although + the user is permitted to override this by using an explicit + `--host' option. + +`host_alias' + In the unusual case that the user used an explicit `--host' option, + this will be the argument to `--host'. In the normal case, this + will be the same as the `host' variable. + +`host_cpu' +`host_vendor' +`host_os' + The first three parts of the canonical configuration name. + + The shell variables may be used by putting shell code in +`configure.in'. For an example, see *note Using Configuration Names::. + + +File: configure.info, Node: Specifying the Target, Next: Using the Target Type, Prev: Using the Host Type, Up: Cross Compilation Tools + +5.4 Specifying the Target +========================= + +By default, the `configure' script will assume that the target is the +same as the host. This is the more common case; for example, it leads +to a native compiler rather than a cross compiler. + + If you want to build a cross compilation tool, you must specify the +target explicitly by using the `--target' option when you run +`configure'. The argument to `--target' is the configuration name of +the system for which you wish to generate code. *Note Configuration +Names::. + + For example, to build tools which generate code for a MIPS ELF +embedded system, you would use `--target mips-elf'. + + +File: configure.info, Node: Using the Target Type, Next: Cross Tools in the Cygnus Tree, Prev: Specifying the Target, Up: Cross Compilation Tools + +5.5 Using the Target Type +========================= + +When writing `configure.in' for a cross compilation tool, you will need +to use information about the target. To do this, put +`AC_CANONICAL_SYSTEM' in `configure.in'. + + `AC_CANONICAL_SYSTEM' will look for a `--target' option and +canonicalize it using the `config.sub' shell script. It will also run +`AC_CANONICAL_HOST' (*note Using the Host Type::). + + The target type will be recorded in the following shell variables. +Note that the host versions of these variables will also be defined by +`AC_CANONICAL_HOST'. + +`target' + The canonical configuration name of the target. + +`target_alias' + The argument to the `--target' option. If the user did not specify + a `--target' option, this will be the same as `host_alias'. + +`target_cpu' +`target_vendor' +`target_os' + The first three parts of the canonical target configuration name. + + Note that if `host' and `target' are the same string, you can assume +a native configuration. If they are different, you can assume a cross +configuration. + + It is arguably possible for `host' and `target' to represent the +same system, but for the strings to not be identical. For example, if +`config.guess' returns `sparc-sun-sunos4.1.4', and somebody configures +with `--target sparc-sun-sunos4.1', then the slight differences between +the two versions of SunOS may be unimportant for your tool. However, +in the general case it can be quite difficult to determine whether the +differences between two configuration names are significant or not. +Therefore, by convention, if the user specifies a `--target' option +without specifying a `--host' option, it is assumed that the user wants +to configure a cross compilation tool. + + The variables `target' and `target_alias' should be handled +differently. + + In general, whenever the user may actually see a string, +`target_alias' should be used. This includes anything which may appear +in the file system, such as a directory name or part of a tool name. +It also includes any tool output, unless it is clearly labelled as the +canonical target configuration name. This permits the user to use the +`--target' option to specify how the tool will appear to the outside +world. + + On the other hand, when checking for characteristics of the target +system, `target' should be used. This is because a wide variety of +`--target' options may map into the same canonical configuration name. +You should not attempt to duplicate the canonicalization done by +`config.sub' in your own code. + + By convention, cross tools are installed with a prefix of the +argument used with the `--target' option, also known as `target_alias' +(*note Using the Target Type::). If the user does not use the +`--target' option, and thus is building a native tool, no prefix is +used. + + For example, if gcc is configured with `--target mips-elf', then the +installed binary will be named `mips-elf-gcc'. If gcc is configured +without a `--target' option, then the installed binary will be named +`gcc'. + + The autoconf macro `AC_ARG_PROGRAM' will handle this for you. If +you are using automake, no more need be done; the programs will +automatically be installed with the correct prefixes. Otherwise, see +the autoconf documentation for `AC_ARG_PROGRAM'. + + +File: configure.info, Node: Cross Tools in the Cygnus Tree, Prev: Using the Target Type, Up: Cross Compilation Tools + +5.6 Cross Tools in the Cygnus Tree +================================== + +The Cygnus tree is used for various packages including gdb, the GNU +binutils, and egcs. It is also, of course, used for Cygnus releases. + + In the Cygnus tree, the top level `configure' script uses the old +Cygnus configure system, not autoconf. The top level `Makefile.in' is +written to build packages based on what is in the source tree, and +supports building a large number of tools in a single +`configure'/`make' step. + + The Cygnus tree may be configured with a `--target' option. The +`--target' option applies recursively to every subdirectory, and +permits building an entire set of cross tools at once. + +* Menu: + +* Host and Target Libraries:: Host and Target Libraries. +* Target Library Configure Scripts:: Target Library Configure Scripts. +* Make Targets in Cygnus Tree:: Make Targets in Cygnus Tree. +* Target libiberty:: Target libiberty + + +File: configure.info, Node: Host and Target Libraries, Next: Target Library Configure Scripts, Up: Cross Tools in the Cygnus Tree + +5.6.1 Host and Target Libraries +------------------------------- + +The Cygnus tree distinguishes host libraries from target libraries. + + Host libraries are built with the compiler used to build the programs +which run on the host, which is called the host compiler. This includes +libraries such as `bfd' and `tcl'. These libraries are built with the +host compiler, and are linked into programs like the binutils or gcc +which run on the host. + + Target libraries are built with the target compiler. If gcc is +present in the source tree, then the target compiler is the gcc that is +built using the host compiler. Target libraries are libraries such as +`newlib' and `libstdc++'. These libraries are not linked into the host +programs, but are instead made available for use with programs built +with the target compiler. + + For the rest of this section, assume that gcc is present in the +source tree, so that it will be used to build the target libraries. + + There is a complication here. The configure process needs to know +which compiler you are going to use to build a tool; otherwise, the +feature tests will not work correctly. The Cygnus tree handles this by +not configuring the target libraries until the target compiler is +built. In order to permit everything to build using a single +`configure'/`make', the configuration of the target libraries is +actually triggered during the make step. + + When the target libraries are configured, the `--target' option is +not used. Instead, the `--host' option is used with the argument of +the `--target' option for the overall configuration. If no `--target' +option was used for the overall configuration, the `--host' option will +be passed with the output of the `config.guess' shell script. Any +`--build' option is passed down unchanged. + + This translation of configuration options is done because since the +target libraries are compiled with the target compiler, they are being +built in order to run on the target of the overall configuration. By +the definition of host, this means that their host system is the same as +the target system of the overall configuration. + + The same process is used for both a native configuration and a cross +configuration. Even when using a native configuration, the target +libraries will be configured and built using the newly built compiler. +This is particularly important for the C++ libraries, since there is no +reason to assume that the C++ compiler used to build the host tools (if +there even is one) uses the same ABI as the g++ compiler which will be +used to build the target libraries. + + There is one difference between a native configuration and a cross +configuration. In a native configuration, the target libraries are +normally configured and built as siblings of the host tools. In a cross +configuration, the target libraries are normally built in a subdirectory +whose name is the argument to `--target'. This is mainly for +historical reasons. + + To summarize, running `configure' in the Cygnus tree configures all +the host libraries and tools, but does not configure any of the target +libraries. Running `make' then does the following steps: + + * Build the host libraries. + + * Build the host programs, including gcc. Note that we call gcc + both a host program (since it runs on the host) and a target + compiler (since it generates code for the target). + + * Using the newly built target compiler, configure the target + libraries. + + * Build the target libraries. + + The steps need not be done in precisely this order, since they are +actually controlled by `Makefile' targets. + + +File: configure.info, Node: Target Library Configure Scripts, Next: Make Targets in Cygnus Tree, Prev: Host and Target Libraries, Up: Cross Tools in the Cygnus Tree + +5.6.2 Target Library Configure Scripts +-------------------------------------- + +There are a few things you must know in order to write a configure +script for a target library. This is just a quick sketch, and beginners +shouldn't worry if they don't follow everything here. + + The target libraries are configured and built using a newly built +target compiler. There may not be any startup files or libraries for +this target compiler. In fact, those files will probably be built as +part of some target library, which naturally means that they will not +exist when your target library is configured. + + This means that the configure script for a target library may not use +any test which requires doing a link. This unfortunately includes many +useful autoconf macros, such as `AC_CHECK_FUNCS'. autoconf macros +which do a compile but not a link, such as `AC_CHECK_HEADERS', may be +used. + + This is a severe restriction, but normally not a fatal one, as target +libraries can often assume the presence of other target libraries, and +thus know which functions will be available. + + As of this writing, the autoconf macro `AC_PROG_CC' does a link to +make sure that the compiler works. This may fail in a target library, +so target libraries must use a different set of macros to locate the +compiler. See the `configure.in' file in a directory like `libiberty' +or `libgloss' for an example. + + As noted in the previous section, target libraries are sometimes +built in directories which are siblings to the host tools, and are +sometimes built in a subdirectory. The `--with-target-subdir' configure +option will be passed when the library is configured. Its value will be +an empty string if the target library is a sibling. Its value will be +the name of the subdirectory if the target library is in a subdirectory. + + If the overall build is not a native build (i.e., the overall +configure used the `--target' option), then the library will be +configured with the `--with-cross-host' option. The value of this +option will be the host system of the overall build. Recall that the +host system of the library will be the target of the overall build. If +the overall build is a native build, the `--with-cross-host' option +will not be used. + + A library which can be built both standalone and as a target library +may want to install itself into different directories depending upon the +case. When built standalone, or when built native, the library should +be installed in `$(libdir)'. When built as a target library which is +not native, the library should be installed in `$(tooldir)/lib'. The +`--with-cross-host' option may be used to distinguish these cases. + + This same test of `--with-cross-host' may be used to see whether it +is OK to use link tests in the configure script. If the +`--with-cross-host' option is not used, then the library is being built +either standalone or native, and a link should work. + + +File: configure.info, Node: Make Targets in Cygnus Tree, Next: Target libiberty, Prev: Target Library Configure Scripts, Up: Cross Tools in the Cygnus Tree + +5.6.3 Make Targets in Cygnus Tree +--------------------------------- + +The top level `Makefile' in the Cygnus tree defines targets for every +known subdirectory. + + For every subdirectory DIR which holds a host library or program, +the `Makefile' target `all-DIR' will build that library or program. + + There are dependencies among host tools. For example, building gcc +requires first building gas, because the gcc build process invokes the +target assembler. These dependencies are reflected in the top level +`Makefile'. + + For every subdirectory DIR which holds a target library, the +`Makefile' target `configure-target-DIR' will configure that library. +The `Makefile' target `all-target-DIR' will build that library. + + Every `configure-target-DIR' target depends upon `all-gcc', since +gcc, the target compiler, is required to configure the tool. Every +`all-target-DIR' target depends upon the corresponding +`configure-target-DIR' target. + + There are several other targets which may be of interest for each +directory: `install-DIR', `clean-DIR', and `check-DIR'. There are also +corresponding `target' versions of these for the target libraries , +such as `install-target-DIR'. + + +File: configure.info, Node: Target libiberty, Prev: Make Targets in Cygnus Tree, Up: Cross Tools in the Cygnus Tree + +5.6.4 Target libiberty +---------------------- + +The `libiberty' subdirectory is currently a special case, in that it is +the only directory which is built both using the host compiler and +using the target compiler. + + This is because the files in `libiberty' are used when building the +host tools, and they are also incorporated into the `libstdc++' target +library as support code. + + This duality does not pose any particular difficulties. It means +that there are targets for both `all-libiberty' and +`all-target-libiberty'. + + In a native configuration, when target libraries are not built in a +subdirectory, the same objects are normally used as both the host build +and the target build. This is normally OK, since libiberty contains +only C code, and in a native configuration the results of the host +compiler and the target compiler are normally interoperable. + + Irix 6 is again an exception here, since the SGI native compiler +defaults to using the `O32' ABI, and gcc defaults to using the `N32' +ABI. On Irix 6, the target libraries are built in a subdirectory even +for a native configuration, avoiding this problem. + + There are currently no other libraries built for both the host and +the target, but there is no conceptual problem with adding more. + + +File: configure.info, Node: Canadian Cross, Next: Cygnus Configure, Prev: Cross Compilation Tools, Up: Top + +6 Canadian Cross +**************** + +It is possible to use the GNU configure and build system to build a +program which will run on a system which is different from the system on +which the tools are built. In other words, it is possible to build +programs using a cross compiler. + + This is referred to as a "Canadian Cross". + +* Menu: + +* Canadian Cross Example:: Canadian Cross Example. +* Canadian Cross Concepts:: Canadian Cross Concepts. +* Build Cross Host Tools:: Build Cross Host Tools. +* Build and Host Options:: Build and Host Options. +* CCross not in Cygnus Tree:: Canadian Cross not in Cygnus Tree. +* CCross in Cygnus Tree:: Canadian Cross in Cygnus Tree. +* Supporting Canadian Cross:: Supporting Canadian Cross. + + +File: configure.info, Node: Canadian Cross Example, Next: Canadian Cross Concepts, Up: Canadian Cross + +6.1 Canadian Cross Example +========================== + +Here is an example of a Canadian Cross. + + While running on a GNU/Linux, you can build a program which will run +on a Solaris system. You would use a GNU/Linux cross Solaris compiler +to build the program. + + Of course, you could not run the resulting program on your GNU/Linux +system. You would have to copy it over to a Solaris system before you +would run it. + + Of course, you could also simply build the programs on the Solaris +system in the first place. However, perhaps the Solaris system is not +available for some reason; perhaps you actually don't have one, but you +want to build the tools for somebody else to use. Or perhaps your +GNU/Linux system is much faster than your Solaris system. + + A Canadian Cross build is most frequently used when building +programs to run on a non-Unix system, such as DOS or Windows. It may +be simpler to configure and build on a Unix system than to support the +configuration machinery on a non-Unix system. + + +File: configure.info, Node: Canadian Cross Concepts, Next: Build Cross Host Tools, Prev: Canadian Cross Example, Up: Canadian Cross + +6.2 Canadian Cross Concepts +=========================== + +When building a Canadian Cross, there are at least two different systems +involved: the system on which the tools are being built, and the system +on which the tools will run. + + The system on which the tools are being built is called the "build" +system. + + The system on which the tools will run is called the host system. + + For example, if you are building a Solaris program on a GNU/Linux +system, as in the previous section, the build system would be GNU/Linux, +and the host system would be Solaris. + + It is, of course, possible to build a cross compiler using a Canadian +Cross (i.e., build a cross compiler using a cross compiler). In this +case, the system for which the resulting cross compiler generates code +is called the target system. (For a more complete discussion of host +and target systems, *note Host and Target::). + + An example of building a cross compiler using a Canadian Cross would +be building a Windows cross MIPS ELF compiler on a GNU/Linux system. In +this case the build system would be GNU/Linux, the host system would be +Windows, and the target system would be MIPS ELF. + + The name Canadian Cross comes from the case when the build, host, and +target systems are all different. At the time that these issues were +all being hashed out, Canada had three national political parties. + + +File: configure.info, Node: Build Cross Host Tools, Next: Build and Host Options, Prev: Canadian Cross Concepts, Up: Canadian Cross + +6.3 Build Cross Host Tools +========================== + +In order to configure a program for a Canadian Cross build, you must +first build and install the set of cross tools you will use to build the +program. + + These tools will be build cross host tools. That is, they will run +on the build system, and will produce code that runs on the host system. + + It is easy to confuse the meaning of build and host here. Always +remember that the build system is where you are doing the build, and the +host system is where the resulting program will run. Therefore, you +need a build cross host compiler. + + In general, you must have a complete cross environment in order to do +the build. This normally means a cross compiler, cross assembler, and +so forth, as well as libraries and include files for the host system. + + +File: configure.info, Node: Build and Host Options, Next: CCross not in Cygnus Tree, Prev: Build Cross Host Tools, Up: Canadian Cross + +6.4 Build and Host Options +========================== + +When you run `configure', you must use both the `--build' and `--host' +options. + + The `--build' option is used to specify the configuration name of +the build system. This can normally be the result of running the +`config.guess' shell script, and it is reasonable to use +`--build=`config.guess`'. + + The `--host' option is used to specify the configuration name of the +host system. + + As we explained earlier, `config.guess' is used to set the default +value for the `--host' option (*note Using the Host Type::). We can +now see that since `config.guess' returns the type of system on which +it is run, it really identifies the build system. Since the host +system is normally the same as the build system (i.e., people do not +normally build using a cross compiler), it is reasonable to use the +result of `config.guess' as the default for the host system when the +`--host' option is not used. + + It might seem that if the `--host' option were used without the +`--build' option that the configure script could run `config.guess' to +determine the build system, and presume a Canadian Cross if the result +of `config.guess' differed from the `--host' option. However, for +historical reasons, some configure scripts are routinely run using an +explicit `--host' option, rather than using the default from +`config.guess'. As noted earlier, it is difficult or impossible to +reliably compare configuration names (*note Using the Target Type::). +Therefore, by convention, if the `--host' option is used, but the +`--build' option is not used, then the build system defaults to the +host system. + + +File: configure.info, Node: CCross not in Cygnus Tree, Next: CCross in Cygnus Tree, Prev: Build and Host Options, Up: Canadian Cross + +6.5 Canadian Cross not in Cygnus Tree. +====================================== + +If you are not using the Cygnus tree, you must explicitly specify the +cross tools which you want to use to build the program. This is done by +setting environment variables before running the `configure' script. + + You must normally set at least the environment variables `CC', `AR', +and `RANLIB' to the cross tools which you want to use to build. + + For some programs, you must set additional cross tools as well, such +as `AS', `LD', or `NM'. + + You would set these environment variables to the build cross tools +which you are going to use. + + For example, if you are building a Solaris program on a GNU/Linux +system, and your GNU/Linux cross Solaris compiler were named +`solaris-gcc', then you would set the environment variable `CC' to +`solaris-gcc'. + + +File: configure.info, Node: CCross in Cygnus Tree, Next: Supporting Canadian Cross, Prev: CCross not in Cygnus Tree, Up: Canadian Cross + +6.6 Canadian Cross in Cygnus Tree +================================= + +This section describes configuring and building a Canadian Cross when +using the Cygnus tree. + +* Menu: + +* Standard Cygnus CCross:: Building a Normal Program. +* Cross Cygnus CCross:: Building a Cross Program. + + +File: configure.info, Node: Standard Cygnus CCross, Next: Cross Cygnus CCross, Up: CCross in Cygnus Tree + +6.6.1 Building a Normal Program +------------------------------- + +When configuring a Canadian Cross in the Cygnus tree, all the +appropriate environment variables are automatically set to `HOST-TOOL', +where HOST is the value used for the `--host' option, and TOOL is the +name of the tool (e.g., `gcc', `as', etc.). These tools must be on +your `PATH'. + + Adding a prefix of HOST will give the usual name for the build cross +host tools. To see this, consider that when these cross tools were +built, they were configured to run on the build system and to produce +code for the host system. That is, they were configured with a +`--target' option that is the same as the system which we are now +calling the host. Recall that the default name for installed cross +tools uses the target system as a prefix (*note Using the Target +Type::). Since that is the system which we are now calling the host, +HOST is the right prefix to use. + + For example, if you configure with `--build=i386-linux-gnu' and +`--host=solaris', then the Cygnus tree will automatically default to +using the compiler `solaris-gcc'. You must have previously built and +installed this compiler, probably by doing a build with no `--host' +option and with a `--target' option of `solaris'. + + +File: configure.info, Node: Cross Cygnus CCross, Prev: Standard Cygnus CCross, Up: CCross in Cygnus Tree + +6.6.2 Building a Cross Program +------------------------------ + +There are additional considerations if you want to build a cross +compiler, rather than a native compiler, in the Cygnus tree using a +Canadian Cross. + + When you build a cross compiler using the Cygnus tree, then the +target libraries will normally be built with the newly built target +compiler (*note Host and Target Libraries::). However, this will not +work when building with a Canadian Cross. This is because the newly +built target compiler will be a program which runs on the host system, +and therefore will not be able to run on the build system. + + Therefore, when building a cross compiler with the Cygnus tree, you +must first install a set of build cross target tools. These tools will +be used when building the target libraries. + + Note that this is not a requirement of a Canadian Cross in general. +For example, it would be possible to build just the host cross target +tools on the build system, to copy the tools to the host system, and to +build the target libraries on the host system. The requirement for +build cross target tools is imposed by the Cygnus tree, which expects +to be able to build both host programs and target libraries in a single +`configure'/`make' step. Because it builds these in a single step, it +expects to be able to build the target libraries on the build system, +which means that it must use a build cross target toolchain. + + For example, suppose you want to build a Windows cross MIPS ELF +compiler on a GNU/Linux system. You must have previously installed +both a GNU/Linux cross Windows compiler and a GNU/Linux cross MIPS ELF +compiler. + + In order to build the Windows (configuration name `i386-cygwin32') +cross MIPS ELF (configure name `mips-elf') compiler, you might execute +the following commands (long command lines are broken across lines with +a trailing backslash as a continuation character). + + mkdir linux-x-cygwin32 + cd linux-x-cygwin32 + SRCDIR/configure --target i386-cygwin32 --prefix=INSTALLDIR \ + --exec-prefix=INSTALLDIR/H-i386-linux + make + make install + cd .. + mkdir linux-x-mips-elf + cd linux-x-mips-elf + SRCDIR/configure --target mips-elf --prefix=INSTALLDIR \ + --exec-prefix=INSTALLDIR/H-i386-linux + make + make install + cd .. + mkdir cygwin32-x-mips-elf + cd cygwin32-x-mips-elf + SRCDIR/configure --build=i386-linux-gnu --host=i386-cygwin32 \ + --target=mips-elf --prefix=WININSTALLDIR \ + --exec-prefix=WININSTALLDIR/H-i386-cygwin32 + make + make install + + You would then copy the contents of WININSTALLDIR over to the +Windows machine, and run the resulting programs. + + +File: configure.info, Node: Supporting Canadian Cross, Prev: CCross in Cygnus Tree, Up: Canadian Cross + +6.7 Supporting Canadian Cross +============================= + +If you want to make it possible to build a program you are developing +using a Canadian Cross, you must take some care when writing your +configure and make rules. Simple cases will normally work correctly. +However, it is not hard to write configure and make tests which will +fail in a Canadian Cross. + +* Menu: + +* CCross in Configure:: Supporting Canadian Cross in Configure Scripts. +* CCross in Make:: Supporting Canadian Cross in Makefiles. + + +File: configure.info, Node: CCross in Configure, Next: CCross in Make, Up: Supporting Canadian Cross + +6.7.1 Supporting Canadian Cross in Configure Scripts +---------------------------------------------------- + +In a `configure.in' file, after calling `AC_PROG_CC', you can find out +whether this is a Canadian Cross configure by examining the shell +variable `cross_compiling'. In a Canadian Cross, which means that the +compiler is a cross compiler, `cross_compiling' will be `yes'. In a +normal configuration, `cross_compiling' will be `no'. + + You ordinarily do not need to know the type of the build system in a +configure script. However, if you do need that information, you can get +it by using the macro `AC_CANONICAL_SYSTEM', the same macro that is +used to determine the target system. This macro will set the variables +`build', `build_alias', `build_cpu', `build_vendor', and `build_os', +which correspond to the similar `target' and `host' variables, except +that they describe the build system. + + When writing tests in `configure.in', you must remember that you +want to test the host environment, not the build environment. + + Macros like `AC_CHECK_FUNCS' which use the compiler will test the +host environment. That is because the tests will be done by running the +compiler, which is actually a build cross host compiler. If the +compiler can find the function, that means that the function is present +in the host environment. + + Tests like `test -f /dev/ptyp0', on the other hand, will test the +build environment. Remember that the configure script is running on the +build system, not the host system. If your configure scripts examines +files, those files will be on the build system. Whatever you determine +based on those files may or may not be the case on the host system. + + Most autoconf macros will work correctly for a Canadian Cross. The +main exception is `AC_TRY_RUN'. This macro tries to compile and run a +test program. This will fail in a Canadian Cross, because the program +will be compiled for the host system, which means that it will not run +on the build system. + + The `AC_TRY_RUN' macro provides an optional argument to tell the +configure script what to do in a Canadian Cross. If that argument is +not present, you will get a warning when you run `autoconf': + warning: AC_TRY_RUN called without default to allow cross compiling + This tells you that the resulting `configure' script will not work +with a Canadian Cross. + + In some cases while it may better to perform a test at configure +time, it is also possible to perform the test at run time. In such a +case you can use the cross compiling argument to `AC_TRY_RUN' to tell +your program that the test could not be performed at configure time. + + There are a few other autoconf macros which will not work correctly +with a Canadian Cross: a partial list is `AC_FUNC_GETPGRP', +`AC_FUNC_SETPGRP', `AC_FUNC_SETVBUF_REVERSED', and +`AC_SYS_RESTARTABLE_SYSCALLS'. The `AC_CHECK_SIZEOF' macro is +generally not very useful with a Canadian Cross; it permits an optional +argument indicating the default size, but there is no way to know what +the correct default should be. + + +File: configure.info, Node: CCross in Make, Prev: CCross in Configure, Up: Supporting Canadian Cross + +6.7.2 Supporting Canadian Cross in Makefiles. +--------------------------------------------- + +The main Canadian Cross issue in a `Makefile' arises when you want to +use a subsidiary program to generate code or data which you will then +include in your real program. + + If you compile this subsidiary program using `$(CC)' in the usual +way, you will not be able to run it. This is because `$(CC)' will +build a program for the host system, but the program is being built on +the build system. + + You must instead use a compiler for the build system, rather than the +host system. In the Cygnus tree, this make variable `$(CC_FOR_BUILD)' +will hold a compiler for the build system. + + Note that you should not include `config.h' in a file you are +compiling with `$(CC_FOR_BUILD)'. The `configure' script will build +`config.h' with information for the host system. However, you are +compiling the file using a compiler for the build system (a native +compiler). Subsidiary programs are normally simple filters which do no +user interaction, and it is normally possible to write them in a highly +portable fashion so that the absence of `config.h' is not crucial. + + The gcc `Makefile.in' shows a complex situation in which certain +files, such as `rtl.c', must be compiled into both subsidiary programs +run on the build system and into the final program. This approach may +be of interest for advanced build system hackers. Note that the build +system compiler is rather confusingly called `HOST_CC'. + + +File: configure.info, Node: Cygnus Configure, Next: Multilibs, Prev: Canadian Cross, Up: Top + +7 Cygnus Configure +****************** + +The Cygnus configure script predates autoconf. All of its interesting +features have been incorporated into autoconf. No new programs should +be written to use the Cygnus configure script. + + However, the Cygnus configure script is still used in a few places: +at the top of the Cygnus tree and in a few target libraries in the +Cygnus tree. Until those uses have been replaced with autoconf, some +brief notes are appropriate here. This is not complete documentation, +but it should be possible to use this as a guide while examining the +scripts themselves. + +* Menu: + +* Cygnus Configure Basics:: Cygnus Configure Basics. +* Cygnus Configure in C++ Libraries:: Cygnus Configure in C++ Libraries. + + +File: configure.info, Node: Cygnus Configure Basics, Next: Cygnus Configure in C++ Libraries, Up: Cygnus Configure + +7.1 Cygnus Configure Basics +=========================== + +Cygnus configure does not use any generated files; there is no program +corresponding to `autoconf'. Instead, there is a single shell script +named `configure' which may be found at the top of the Cygnus tree. +This shell script was written by hand; it was not generated by +autoconf, and it is incorrect, and indeed harmful, to run `autoconf' in +the top level of a Cygnus tree. + + Cygnus configure works in a particular directory by examining the +file `configure.in' in that directory. That file is broken into four +separate shell scripts. + + The first is the contents of `configure.in' up to a line that starts +with `# per-host:'. This is the common part. + + The second is the rest of `configure.in' up to a line that starts +with `# per-target:'. This is the per host part. + + The third is the rest of `configure.in' up to a line that starts +with `# post-target:'. This is the per target part. + + The fourth is the remainder of `configure.in'. This is the post +target part. + + If any of these comment lines are missing, the corresponding shell +script is empty. + + Cygnus configure will first execute the common part. This must set +the shell variable `srctrigger' to the name of a source file, to +confirm that Cygnus configure is looking at the right directory. This +may set the shell variables `package_makefile_frag' and +`package_makefile_rules_frag'. + + Cygnus configure will next set the `build' and `host' shell +variables, and execute the per host part. This may set the shell +variable `host_makefile_frag'. + + Cygnus configure will next set the `target' variable, and execute +the per target part. This may set the shell variable +`target_makefile_frag'. + + Any of these scripts may set the `subdirs' shell variable. This +variable is a list of subdirectories where a `Makefile.in' file may be +found. Cygnus configure will automatically look for a `Makefile.in' +file in the current directory. The `subdirs' shell variable is not +normally used, and I believe that the only directory which uses it at +present is `newlib'. + + For each `Makefile.in', Cygnus configure will automatically create a +`Makefile' by adding definitions for `make' variables such as `host' +and `target', and automatically editing the values of `make' variables +such as `prefix' if they are present. + + Also, if any of the `makefile_frag' shell variables are set, Cygnus +configure will interpret them as file names relative to either the +working directory or the source directory, and will read the contents of +the file into the generated `Makefile'. The file contents will be read +in after the first line in `Makefile.in' which starts with `####'. + + These `Makefile' fragments are used to customize behaviour for a +particular host or target. They serve to select particular files to +compile, and to define particular preprocessor macros by providing +values for `make' variables which are then used during compilation. +Cygnus configure, unlike autoconf, normally does not do feature tests, +and normally requires support to be added manually for each new host. + + The `Makefile' fragment support is similar to the autoconf +`AC_SUBST_FILE' macro. + + After creating each `Makefile', the post target script will be run +(i.e., it may be run several times). This script may further customize +the `Makefile'. When it is run, the shell variable `Makefile' will +hold the name of the `Makefile', including the appropriate directory +component. + + Like an autoconf generated `configure' script, Cygnus configure will +create a file named `config.status' which, when run, will automatically +recreate the configuration. The `config.status' file will simply +execute the Cygnus configure script again with the appropriate +arguments. + + Any of the parts of `configure.in' may set the shell variables +`files' and `links'. Cygnus configure will set up symlinks from the +names in `links' to the files named in `files'. This is similar to the +autoconf `AC_LINK_FILES' macro. + + Finally, any of the parts of `configure.in' may set the shell +variable `configdirs' to a set of subdirectories. If it is set, Cygnus +configure will recursively run the configure process in each +subdirectory. If the subdirectory uses Cygnus configure, it will +contain a `configure.in' file but no `configure' file, in which case +Cygnus configure will invoke itself recursively. If the subdirectory +has a `configure' file, Cygnus configure assumes that it is an autoconf +generated `configure' script, and simply invokes it directly. + + +File: configure.info, Node: Cygnus Configure in C++ Libraries, Prev: Cygnus Configure Basics, Up: Cygnus Configure + +7.2 Cygnus Configure in C++ Libraries +===================================== + +The C++ library configure system, written by Per Bothner, deserves +special mention. It uses Cygnus configure, but it does feature testing +like that done by autoconf generated `configure' scripts. This +approach is used in the libraries `libio', `libstdc++', and `libg++'. + + Most of the `Makefile' information is written out by the shell +script `libio/config.shared'. Each `configure.in' file sets certain +shell variables, and then invokes `config.shared' to create two package +`Makefile' fragments. These fragments are then incorporated into the +resulting `Makefile' by the Cygnus configure script. + + The file `_G_config.h' is created in the `libio' object directory by +running the shell script `libio/gen-params'. This shell script uses +feature tests to define macros and typedefs in `_G_config.h'. + + +File: configure.info, Node: Multilibs, Next: FAQ, Prev: Cygnus Configure, Up: Top + +8 Multilibs +*********** + +For some targets gcc may have different processor requirements depending +upon command line options. An obvious example is the `-msoft-float' +option supported on several processors. This option means that the +floating point registers are not available, which means that floating +point operations must be done by calling an emulation subroutine rather +than by using machine instructions. + + For such options, gcc is often configured to compile target libraries +twice: once with `-msoft-float' and once without. When gcc compiles +target libraries more than once, the resulting libraries are called +"multilibs". + + Multilibs are not really part of the GNU configure and build system, +but we discuss them here since they require support in the `configure' +scripts and `Makefile's used for target libraries. + +* Menu: + +* Multilibs in gcc:: Multilibs in gcc. +* Multilibs in Target Libraries:: Multilibs in Target Libraries. + + +File: configure.info, Node: Multilibs in gcc, Next: Multilibs in Target Libraries, Up: Multilibs + +8.1 Multilibs in gcc +==================== + +In gcc, multilibs are defined by setting the variable +`MULTILIB_OPTIONS' in the target `Makefile' fragment. Several other +`MULTILIB' variables may also be defined there. *Note The Target +Makefile Fragment: (gcc)Target Fragment. + + If you have built gcc, you can see what multilibs it uses by running +it with the `-print-multi-lib' option. The output `.;' means that no +multilibs are used. In general, the output is a sequence of lines, one +per multilib. The first part of each line, up to the `;', is the name +of the multilib directory. The second part is a list of compiler +options separated by `@' characters. + + Multilibs are built in a tree of directories. The top of the tree, +represented by `.' in the list of multilib directories, is the default +library to use when no special compiler options are used. The +subdirectories of the tree hold versions of the library to use when +particular compiler options are used. + + +File: configure.info, Node: Multilibs in Target Libraries, Prev: Multilibs in gcc, Up: Multilibs + +8.2 Multilibs in Target Libraries +================================= + +The target libraries in the Cygnus tree are automatically built with +multilibs. That means that each library is built multiple times. + + This default is set in the top level `configure.in' file, by adding +`--enable-multilib' to the list of arguments passed to configure when +it is run for the target libraries (*note Host and Target Libraries::). + + Each target library uses the shell script `config-ml.in', written by +Doug Evans, to prepare to build target libraries. This shell script is +invoked after the `Makefile' has been created by the `configure' +script. If multilibs are not enabled, it does nothing, otherwise it +modifies the `Makefile' to support multilibs. + + The `config-ml.in' script makes one copy of the `Makefile' for each +multilib in the appropriate subdirectory. When configuring in the +source directory (which is not recommended), it will build a symlink +tree of the sources in each subdirectory. + + The `config-ml.in' script sets several variables in the various +`Makefile's. The `Makefile.in' must have definitions for these +variables already; `config-ml.in' simply changes the existing values. +The `Makefile' should use default values for these variables which will +do the right thing in the subdirectories. + +`MULTISRCTOP' + `config-ml.in' will set this to a sequence of `../' strings, where + the number of strings is the number of multilib levels in the + source tree. The default value should be the empty string. + +`MULTIBUILDTOP' + `config-ml.in' will set this to a sequence of `../' strings, where + the number of strings is number of multilib levels in the object + directory. The default value should be the empty string. This + will differ from `MULTISRCTOP' when configuring in the source tree + (which is not recommended). + +`MULTIDIRS' + In the top level `Makefile' only, `config-ml.in' will set this to + the list of multilib subdirectories. The default value should be + the empty string. + +`MULTISUBDIR' + `config-ml.in' will set this to the installed subdirectory name to + use for this subdirectory, with a leading `/'. The default value + shold be the empty string. + +`MULTIDO' +`MULTICLEAN' + In the top level `Makefile' only, `config-ml.in' will set these + variables to commands to use when doing a recursive make. These + variables should both default to the string `true', so that by + default nothing happens. + + All references to the parent of the source directory should use the +variable `MULTISRCTOP'. Instead of writing `$(srcdir)/..', you must +write `$(srcdir)/$(MULTISRCTOP)..'. + + Similarly, references to the parent of the object directory should +use the variable `MULTIBUILDTOP'. + + In the installation target, the libraries should be installed in the +subdirectory `MULTISUBDIR'. Instead of installing +`$(libdir)/libfoo.a', install `$(libdir)$(MULTISUBDIR)/libfoo.a'. + + The `config-ml.in' script also modifies the top level `Makefile' to +add `multi-do' and `multi-clean' targets which are used when building +multilibs. + + The default target of the `Makefile' should include the following +command: + @$(MULTIDO) $(FLAGS_TO_PASS) DO=all multi-do + This assumes that `$(FLAGS_TO_PASS)' is defined as a set of +variables to pass to a recursive invocation of `make'. This will build +all the multilibs. Note that the default value of `MULTIDO' is `true', +so by default this command will do nothing. It will only do something +in the top level `Makefile' if multilibs were enabled. + + The `install' target of the `Makefile' should include the following +command: + @$(MULTIDO) $(FLAGS_TO_PASS) DO=install multi-do + + In general, any operation, other than clean, which should be +performed on all the multilibs should use a `$(MULTIDO)' line, setting +the variable `DO' to the target of each recursive call to `make'. + + The `clean' targets (`clean', `mostlyclean', etc.) should use +`$(MULTICLEAN)'. For example, the `clean' target should do this: + @$(MULTICLEAN) DO=clean multi-clean + + +File: configure.info, Node: FAQ, Next: Index, Prev: Multilibs, Up: Top + +9 Frequently Asked Questions +**************************** + +Which do I run first, `autoconf' or `automake'? + Except when you first add autoconf or automake support to a + package, you shouldn't run either by hand. Instead, configure + with the `--enable-maintainer-mode' option, and let `make' take + care of it. + +`autoconf' says something about undefined macros. + This means that you have macros in your `configure.in' which are + not defined by `autoconf'. You may be using an old version of + `autoconf'; try building and installing a newer one. Make sure the + newly installled `autoconf' is first on your `PATH'. Also, see + the next question. + +My `configure' script has stuff like `CY_GNU_GETTEXT' in it. + This means that you have macros in your `configure.in' which should + be defined in your `aclocal.m4' file, but aren't. This usually + means that `aclocal' was not able to appropriate definitions of the + macros. Make sure that you have installed all the packages you + need. In particular, make sure that you have installed libtool + (this is where `AM_PROG_LIBTOOL' is defined) and gettext (this is + where `CY_GNU_GETTEXT' is defined, at least in the Cygnus version + of gettext). + +My `Makefile' has `@' characters in it. + This may mean that you tried to use an autoconf substitution in + your `Makefile.in' without adding the appropriate `AC_SUBST' call + to your `configure' script. Or it may just mean that you need to + rebuild `Makefile' in your build directory. To rebuild `Makefile' + from `Makefile.in', run the shell script `config.status' with no + arguments. If you need to force `configure' to run again, first + run `config.status --recheck'. These runs are normally done + automatically by `Makefile' targets, but if your `Makefile' has + gotten messed up you'll need to help them along. + +Why do I have to run both `config.status --recheck' and `config.status'? + Normally, you don't; they will be run automatically by `Makefile' + targets. If you do need to run them, use `config.status --recheck' + to run the `configure' script again with the same arguments as the + first time you ran it. Use `config.status' (with no arguments) to + regenerate all files (`Makefile', `config.h', etc.) based on the + results of the configure script. The two cases are separate + because it isn't always necessary to regenerate all the files + after running `config.status --recheck'. The `Makefile' targets + generated by automake will use the environment variables + `CONFIG_FILES' and `CONFIG_HEADERS' to only regenerate files as + they are needed. + +What is the Cygnus tree? + The Cygnus tree is used for various packages including gdb, the GNU + binutils, and egcs. It is also, of course, used for Cygnus + releases. It is the build system which was developed at Cygnus, + using the Cygnus configure script. It permits building many + different packages with a single configure and make. The + configure scripts in the tree are being converted to autoconf, but + the general build structure remains intact. + +Why do I have to keep rebuilding and reinstalling the tools? + I know, it's a pain. Unfortunately, there are bugs in the tools + themselves which need to be fixed, and each time that happens + everybody who uses the tools need to reinstall new versions of + them. I don't know if there is going to be a clever fix until the + tools stabilize. + +Why not just have a Cygnus tree `make' target to update the tools? + The tools unfortunately need to be installed before they can be + used. That means that they must be built using an appropriate + prefix, and it seems unwise to assume that every configuration + uses an appropriate prefix. It might be possible to make them + work in place, or it might be possible to install them in some + subdirectory; so far these approaches have not been implemented. + + +File: configure.info, Node: Index, Prev: FAQ, Up: Top + +Index +***** + + +* Menu: + +* --build option: Build and Host Options. + (line 9) +* --host option: Build and Host Options. + (line 14) +* --target option: Specifying the Target. + (line 10) +* _GNU_SOURCE: Write configure.in. (line 134) +* AC_CANONICAL_HOST: Using the Host Type. (line 10) +* AC_CANONICAL_SYSTEM: Using the Target Type. + (line 6) +* AC_CONFIG_HEADER: Write configure.in. (line 66) +* AC_EXEEXT: Write configure.in. (line 86) +* AC_INIT: Write configure.in. (line 38) +* AC_OUTPUT: Write configure.in. (line 142) +* AC_PREREQ: Write configure.in. (line 42) +* AC_PROG_CC: Write configure.in. (line 103) +* AC_PROG_CXX: Write configure.in. (line 117) +* acconfig.h: Written Developer Files. + (line 27) +* acconfig.h, writing: Write acconfig.h. (line 6) +* acinclude.m4: Written Developer Files. + (line 37) +* aclocal.m4: Generated Developer Files. + (line 33) +* AM_CONFIG_HEADER: Write configure.in. (line 53) +* AM_DISABLE_SHARED: Write configure.in. (line 127) +* AM_EXEEXT: Write configure.in. (line 86) +* AM_INIT_AUTOMAKE: Write configure.in. (line 48) +* AM_MAINTAINER_MODE: Write configure.in. (line 70) +* AM_PROG_LIBTOOL: Write configure.in. (line 122) +* AM_PROG_LIBTOOL in configure: FAQ. (line 19) +* build option: Build and Host Options. + (line 9) +* building with a cross compiler: Canadian Cross. (line 6) +* canadian cross: Canadian Cross. (line 6) +* canadian cross in configure: CCross in Configure. (line 6) +* canadian cross in cygnus tree: CCross in Cygnus Tree. + (line 6) +* canadian cross in makefile: CCross in Make. (line 6) +* canadian cross, configuring: Build and Host Options. + (line 6) +* canonical system names: Configuration Names. (line 6) +* config.cache: Build Files Description. + (line 28) +* config.h: Build Files Description. + (line 23) +* config.h.in: Generated Developer Files. + (line 45) +* config.in: Generated Developer Files. + (line 45) +* config.status: Build Files Description. + (line 9) +* config.status --recheck: FAQ. (line 40) +* configuration names: Configuration Names. (line 6) +* configuration triplets: Configuration Names. (line 6) +* configure: Generated Developer Files. + (line 21) +* configure build system: Build and Host Options. + (line 9) +* configure host: Build and Host Options. + (line 14) +* configure target: Specifying the Target. + (line 10) +* configure.in: Written Developer Files. + (line 9) +* configure.in, writing: Write configure.in. (line 6) +* configuring a canadian cross: Build and Host Options. + (line 6) +* cross compiler: Cross Compilation Concepts. + (line 6) +* cross compiler, building with: Canadian Cross. (line 6) +* cross tools: Cross Compilation Tools. + (line 6) +* CY_GNU_GETTEXT in configure: FAQ. (line 19) +* cygnus configure: Cygnus Configure. (line 6) +* goals: Goals. (line 6) +* history: History. (line 6) +* host names: Configuration Names. (line 6) +* host option: Build and Host Options. + (line 14) +* host system: Host and Target. (line 6) +* host triplets: Configuration Names. (line 6) +* HOST_CC: CCross in Make. (line 27) +* libg++ configure: Cygnus Configure in C++ Libraries. + (line 6) +* libio configure: Cygnus Configure in C++ Libraries. + (line 6) +* libstdc++ configure: Cygnus Configure in C++ Libraries. + (line 6) +* Makefile: Build Files Description. + (line 18) +* Makefile, garbage characters: FAQ. (line 29) +* Makefile.am: Written Developer Files. + (line 18) +* Makefile.am, writing: Write Makefile.am. (line 6) +* Makefile.in: Generated Developer Files. + (line 26) +* multilibs: Multilibs. (line 6) +* stamp-h: Build Files Description. + (line 41) +* stamp-h.in: Generated Developer Files. + (line 54) +* system names: Configuration Names. (line 6) +* system types: Configuration Names. (line 6) +* target option: Specifying the Target. + (line 10) +* target system: Host and Target. (line 6) +* triplets: Configuration Names. (line 6) +* undefined macros: FAQ. (line 12) + + + +Tag Table: +Node: Top994 +Node: Introduction1522 +Node: Goals2604 +Node: Tools3328 +Node: History4322 +Node: Building7320 +Node: Getting Started10583 +Node: Write configure.in11096 +Node: Write Makefile.am18347 +Node: Write acconfig.h21524 +Node: Generate files23061 +Node: Getting Started Example25027 +Node: Getting Started Example 125782 +Node: Getting Started Example 227703 +Node: Getting Started Example 330698 +Node: Generate Files in Example33062 +Node: Files34152 +Node: Developer Files34763 +Node: Developer Files Picture35143 +Node: Written Developer Files36431 +Node: Generated Developer Files38983 +Node: Build Files42127 +Node: Build Files Picture42788 +Node: Build Files Description43552 +Node: Support Files45558 +Node: Configuration Names48440 +Node: Configuration Name Definition48940 +Node: Using Configuration Names51263 +Node: Cross Compilation Tools53233 +Node: Cross Compilation Concepts53924 +Node: Host and Target54892 +Node: Using the Host Type56393 +Node: Specifying the Target57742 +Node: Using the Target Type58531 +Node: Cross Tools in the Cygnus Tree61962 +Node: Host and Target Libraries63019 +Node: Target Library Configure Scripts66768 +Node: Make Targets in Cygnus Tree69860 +Node: Target libiberty71208 +Node: Canadian Cross72595 +Node: Canadian Cross Example73436 +Node: Canadian Cross Concepts74555 +Node: Build Cross Host Tools76067 +Node: Build and Host Options77019 +Node: CCross not in Cygnus Tree78805 +Node: CCross in Cygnus Tree79783 +Node: Standard Cygnus CCross80204 +Node: Cross Cygnus CCross81568 +Node: Supporting Canadian Cross84368 +Node: CCross in Configure84983 +Node: CCross in Make88151 +Node: Cygnus Configure89754 +Node: Cygnus Configure Basics90589 +Node: Cygnus Configure in C++ Libraries95267 +Node: Multilibs96274 +Node: Multilibs in gcc97319 +Node: Multilibs in Target Libraries98397 +Node: FAQ102588 +Node: Index106688 + +End Tag Table diff --git a/Unix/info/standards.info b/Unix/info/standards.info new file mode 100644 index 0000000..a459aeb --- /dev/null +++ b/Unix/info/standards.info @@ -0,0 +1,4928 @@ +This is standards.info, produced by makeinfo version 4.13 from ../../newlib-1.15.0/etc/standards.texi. + +START-INFO-DIR-ENTRY +* Standards: (standards). GNU coding standards. +END-INFO-DIR-ENTRY + + GNU Coding Standards Copyright (C) 1992, 1993, 1994, 1995, 1996, +1997, 1998, 1999, 2000, 2001 Free Software Foundation, Inc. + + Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.1 or +any later version published by the Free Software Foundation; with no +Invariant Sections, with no Front-Cover Texts, and with no Back-Cover +Texts. A copy of the license is included in the section entitled "GNU +Free Documentation License". + + +File: standards.info, Node: Top, Next: Preface, Prev: (dir), Up: (dir) + +Version +******* + +Last updated February 14, 2002. + +* Menu: + +* Preface:: About the GNU Coding Standards +* Legal Issues:: Keeping Free Software Free +* Design Advice:: General Program Design +* Program Behavior:: Program Behavior for All Programs +* Writing C:: Making The Best Use of C +* Documentation:: Documenting Programs +* Managing Releases:: The Release Process +* References:: References to Non-Free Software or Documentation +* Copying This Manual:: How to Make Copies of This Manual +* Index:: + + +File: standards.info, Node: Preface, Next: Legal Issues, Prev: Top, Up: Top + +1 About the GNU Coding Standards +******************************** + +The GNU Coding Standards were written by Richard Stallman and other GNU +Project volunteers. Their purpose is to make the GNU system clean, +consistent, and easy to install. This document can also be read as a +guide to writing portable, robust and reliable programs. It focuses on +programs written in C, but many of the rules and principles are useful +even if you write in another programming language. The rules often +state reasons for writing in a certain way. + + This release of the GNU Coding Standards was last updated February +14, 2002. + + If you did not obtain this file directly from the GNU project and +recently, please check for a newer version. You can ftp the GNU Coding +Standards from any GNU FTP host in the directory `/pub/gnu/standards/'. +The GNU Coding Standards are available there in several different +formats: `standards.text', `standards.info', and `standards.dvi', as +well as the Texinfo "source" which is divided in two files: +`standards.texi' and `make-stds.texi'. The GNU Coding Standards are +also available on the GNU World Wide Web server: +`http://www.gnu.org/prep/standards_toc.html'. + + Corrections or suggestions for this document should be sent to +<bug-standards@gnu.org>. If you make a suggestion, please include a +suggested new wording for it; our time is limited. We prefer a context +diff to the `standards.texi' or `make-stds.texi' files, but if you +don't have those files, please mail your suggestion anyway. + + These standards cover the minimum of what is important when writing a +GNU package. Likely, the needs for additional standards will come up. +Sometimes, you might suggest that such standards be added to this +document. If you think your standards would be generally useful, please +do suggest them. + + You should also set standards for your package on many questions not +addressed or not firmly specified here. The most important point is to +be self-consistent--try to stick to the conventions you pick, and try +to document them as much as possible. That way, your program will be +more maintainable by others. + + +File: standards.info, Node: Legal Issues, Next: Design Advice, Prev: Preface, Up: Top + +2 Keeping Free Software Free +**************************** + +This node discusses how you can make sure that GNU software avoids +legal difficulties, and other related issues. + +* Menu: + +* Reading Non-Free Code:: Referring to Proprietary Programs +* Contributions:: Accepting Contributions +* Trademarks:: How We Deal with Trademark Issues + + +File: standards.info, Node: Reading Non-Free Code, Next: Contributions, Up: Legal Issues + +2.1 Referring to Proprietary Programs +===================================== + +Don't in any circumstances refer to Unix source code for or during your +work on GNU! (Or to any other proprietary programs.) + + If you have a vague recollection of the internals of a Unix program, +this does not absolutely mean you can't write an imitation of it, but +do try to organize the imitation internally along different lines, +because this is likely to make the details of the Unix version +irrelevant and dissimilar to your results. + + For example, Unix utilities were generally optimized to minimize +memory use; if you go for speed instead, your program will be very +different. You could keep the entire input file in core and scan it +there instead of using stdio. Use a smarter algorithm discovered more +recently than the Unix program. Eliminate use of temporary files. Do +it in one pass instead of two (we did this in the assembler). + + Or, on the contrary, emphasize simplicity instead of speed. For some +applications, the speed of today's computers makes simpler algorithms +adequate. + + Or go for generality. For example, Unix programs often have static +tables or fixed-size strings, which make for arbitrary limits; use +dynamic allocation instead. Make sure your program handles NULs and +other funny characters in the input files. Add a programming language +for extensibility and write part of the program in that language. + + Or turn some parts of the program into independently usable +libraries. Or use a simple garbage collector instead of tracking +precisely when to free memory, or use a new GNU facility such as +obstacks. + + +File: standards.info, Node: Contributions, Next: Trademarks, Prev: Reading Non-Free Code, Up: Legal Issues + +2.2 Accepting Contributions +=========================== + +If the program you are working on is copyrighted by the Free Software +Foundation, then when someone else sends you a piece of code to add to +the program, we need legal papers to use it--just as we asked you to +sign papers initially. _Each_ person who makes a nontrivial +contribution to a program must sign some sort of legal papers in order +for us to have clear title to the program; the main author alone is not +enough. + + So, before adding in any contributions from other people, please tell +us, so we can arrange to get the papers. Then wait until we tell you +that we have received the signed papers, before you actually use the +contribution. + + This applies both before you release the program and afterward. If +you receive diffs to fix a bug, and they make significant changes, we +need legal papers for that change. + + This also applies to comments and documentation files. For copyright +law, comments and code are just text. Copyright applies to all kinds of +text, so we need legal papers for all kinds. + + We know it is frustrating to ask for legal papers; it's frustrating +for us as well. But if you don't wait, you are going out on a limb--for +example, what if the contributor's employer won't sign a disclaimer? +You might have to take that code out again! + + You don't need papers for changes of a few lines here or there, since +they are not significant for copyright purposes. Also, you don't need +papers if all you get from the suggestion is some ideas, not actual code +which you use. For example, if someone send you one implementation, but +you write a different implementation of the same idea, you don't need to +get papers. + + The very worst thing is if you forget to tell us about the other +contributor. We could be very embarrassed in court some day as a +result. + + We have more detailed advice for maintainers of programs; if you have +reached the stage of actually maintaining a program for GNU (whether +released or not), please ask us for a copy. + + +File: standards.info, Node: Trademarks, Prev: Contributions, Up: Legal Issues + +2.3 Trademarks +============== + +Please do not include any trademark acknowledgements in GNU software +packages or documentation. + + Trademark acknowledgements are the statements that such-and-such is a +trademark of so-and-so. The GNU Project has no objection to the basic +idea of trademarks, but these acknowledgements feel like kowtowing, so +we don't use them. There is no legal requirement for them. + + What is legally required, as regards other people's trademarks, is to +avoid using them in ways which a reader might read as naming or labeling +our own programs or activities. For example, since "Objective C" is +(or at least was) a trademark, we made sure to say that we provide a +"compiler for the Objective C language" rather than an "Objective C +compiler". The latter is meant to be short for the former, but it does +not explicitly state the relationship, so it could be misinterpreted as +using "Objective C" as a label for the compiler rather than for the +language. + + +File: standards.info, Node: Design Advice, Next: Program Behavior, Prev: Legal Issues, Up: Top + +3 General Program Design +************************ + +This node discusses some of the issues you should take into account +when designing your program. + +* Menu: + +* Source Language:: Which languges to use. +* Compatibility:: Compatibility with other implementations +* Using Extensions:: Using non-standard features +* Standard C:: Using Standard C features +* Conditional Compilation:: Compiling Code Only If A Conditional is True + + +File: standards.info, Node: Source Language, Next: Compatibility, Up: Design Advice + +3.1 Which Languages to Use +========================== + +When you want to use a language that gets compiled and runs at high +speed, the best language to use is C. Using another language is like +using a non-standard feature: it will cause trouble for users. Even if +GCC supports the other language, users may find it inconvenient to have +to install the compiler for that other language in order to build your +program. For example, if you write your program in C++, people will +have to install the GNU C++ compiler in order to compile your program. + + C has one other advantage over C++ and other compiled languages: more +people know C, so more people will find it easy to read and modify the +program if it is written in C. + + So in general it is much better to use C, rather than the comparable +alternatives. + + But there are two exceptions to that conclusion: + + * It is no problem to use another language to write a tool + specifically intended for use with that language. That is because + the only people who want to build the tool will be those who have + installed the other language anyway. + + * If an application is of interest only to a narrow part of the + community, then the question of which language it is written in + has less effect on other people, so you may as well please + yourself. + + Many programs are designed to be extensible: they include an +interpreter for a language that is higher level than C. Often much of +the program is written in that language, too. The Emacs editor +pioneered this technique. + + The standard extensibility interpreter for GNU software is GUILE, +which implements the language Scheme (an especially clean and simple +dialect of Lisp). `http://www.gnu.org/software/guile/'. We don't +reject programs written in other "scripting languages" such as Perl and +Python, but using GUILE is very important for the overall consistency of +the GNU system. + + +File: standards.info, Node: Compatibility, Next: Using Extensions, Prev: Source Language, Up: Design Advice + +3.2 Compatibility with Other Implementations +============================================ + +With occasional exceptions, utility programs and libraries for GNU +should be upward compatible with those in Berkeley Unix, and upward +compatible with Standard C if Standard C specifies their behavior, and +upward compatible with POSIX if POSIX specifies their behavior. + + When these standards conflict, it is useful to offer compatibility +modes for each of them. + + Standard C and POSIX prohibit many kinds of extensions. Feel free +to make the extensions anyway, and include a `--ansi', `--posix', or +`--compatible' option to turn them off. However, if the extension has +a significant chance of breaking any real programs or scripts, then it +is not really upward compatible. So you should try to redesign its +interface to make it upward compatible. + + Many GNU programs suppress extensions that conflict with POSIX if the +environment variable `POSIXLY_CORRECT' is defined (even if it is +defined with a null value). Please make your program recognize this +variable if appropriate. + + When a feature is used only by users (not by programs or command +files), and it is done poorly in Unix, feel free to replace it +completely with something totally different and better. (For example, +`vi' is replaced with Emacs.) But it is nice to offer a compatible +feature as well. (There is a free `vi' clone, so we offer it.) + + Additional useful features are welcome regardless of whether there +is any precedent for them. + + +File: standards.info, Node: Using Extensions, Next: Standard C, Prev: Compatibility, Up: Design Advice + +3.3 Using Non-standard Features +=============================== + +Many GNU facilities that already exist support a number of convenient +extensions over the comparable Unix facilities. Whether to use these +extensions in implementing your program is a difficult question. + + On the one hand, using the extensions can make a cleaner program. +On the other hand, people will not be able to build the program unless +the other GNU tools are available. This might cause the program to +work on fewer kinds of machines. + + With some extensions, it might be easy to provide both alternatives. +For example, you can define functions with a "keyword" `INLINE' and +define that as a macro to expand into either `inline' or nothing, +depending on the compiler. + + In general, perhaps it is best not to use the extensions if you can +straightforwardly do without them, but to use the extensions if they +are a big improvement. + + An exception to this rule are the large, established programs (such +as Emacs) which run on a great variety of systems. Using GNU +extensions in such programs would make many users unhappy, so we don't +do that. + + Another exception is for programs that are used as part of +compilation: anything that must be compiled with other compilers in +order to bootstrap the GNU compilation facilities. If these require +the GNU compiler, then no one can compile them without having them +installed already. That would be extremely troublesome in certain +cases. + + +File: standards.info, Node: Standard C, Next: Conditional Compilation, Prev: Using Extensions, Up: Design Advice + +3.4 Standard C and Pre-Standard C +================================= + +1989 Standard C is widespread enough now that it is ok to use its +features in new programs. There is one exception: do not ever use the +"trigraph" feature of Standard C. + + 1999 Standard C is not widespread yet, so please do not require its +features in programs. It is ok to use its features if they are present. + + However, it is easy to support pre-standard compilers in most +programs, so if you know how to do that, feel free. If a program you +are maintaining has such support, you should try to keep it working. + + To support pre-standard C, instead of writing function definitions in +standard prototype form, + + int + foo (int x, int y) + ... + +write the definition in pre-standard style like this, + + int + foo (x, y) + int x, y; + ... + +and use a separate declaration to specify the argument prototype: + + int foo (int, int); + + You need such a declaration anyway, in a header file, to get the +benefit of prototypes in all the files where the function is called. +And once you have the declaration, you normally lose nothing by writing +the function definition in the pre-standard style. + + This technique does not work for integer types narrower than `int'. +If you think of an argument as being of a type narrower than `int', +declare it as `int' instead. + + There are a few special cases where this technique is hard to use. +For example, if a function argument needs to hold the system type +`dev_t', you run into trouble, because `dev_t' is shorter than `int' on +some machines; but you cannot use `int' instead, because `dev_t' is +wider than `int' on some machines. There is no type you can safely use +on all machines in a non-standard definition. The only way to support +non-standard C and pass such an argument is to check the width of +`dev_t' using Autoconf and choose the argument type accordingly. This +may not be worth the trouble. + + In order to support pre-standard compilers that do not recognize +prototypes, you may want to use a preprocessor macro like this: + + /* Declare the prototype for a general external function. */ + #if defined (__STDC__) || defined (WINDOWSNT) + #define P_(proto) proto + #else + #define P_(proto) () + #endif + + +File: standards.info, Node: Conditional Compilation, Prev: Standard C, Up: Design Advice + +3.5 Conditional Compilation +=========================== + +When supporting configuration options already known when building your +program we prefer using `if (... )' over conditional compilation, as in +the former case the compiler is able to perform more extensive checking +of all possible code paths. + + For example, please write + + if (HAS_FOO) + ... + else + ... + + instead of: + + #ifdef HAS_FOO + ... + #else + ... + #endif + + A modern compiler such as GCC will generate exactly the same code in +both cases, and we have been using similar techniques with good success +in several projects. + + While this is not a silver bullet solving all portability problems, +following this policy would have saved the GCC project alone many person +hours if not days per year. + + In the case of function-like macros like `REVERSIBLE_CC_MODE' in GCC +which cannot be simply used in `if( ...)' statements, there is an easy +workaround. Simply introduce another macro `HAS_REVERSIBLE_CC_MODE' as +in the following example: + + #ifdef REVERSIBLE_CC_MODE + #define HAS_REVERSIBLE_CC_MODE 1 + #else + #define HAS_REVERSIBLE_CC_MODE 0 + #endif + + +File: standards.info, Node: Program Behavior, Next: Writing C, Prev: Design Advice, Up: Top + +4 Program Behavior for All Programs +*********************************** + +This node describes conventions for writing robust software. It also +describes general standards for error messages, the command line +interface, and how libraries should behave. + +* Menu: + +* Semantics:: Writing robust programs +* Libraries:: Library behavior +* Errors:: Formatting error messages +* User Interfaces:: Standards about interfaces generally +* Graphical Interfaces:: Standards for graphical interfaces +* Command-Line Interfaces:: Standards for command line interfaces +* Option Table:: Table of long options +* Memory Usage:: When and how to care about memory needs +* File Usage:: Which files to use, and where + + +File: standards.info, Node: Semantics, Next: Libraries, Up: Program Behavior + +4.1 Writing Robust Programs +=========================== + +Avoid arbitrary limits on the length or number of _any_ data structure, +including file names, lines, files, and symbols, by allocating all data +structures dynamically. In most Unix utilities, "long lines are +silently truncated". This is not acceptable in a GNU utility. + + Utilities reading files should not drop NUL characters, or any other +nonprinting characters _including those with codes above 0177_. The +only sensible exceptions would be utilities specifically intended for +interface to certain types of terminals or printers that can't handle +those characters. Whenever possible, try to make programs work +properly with sequences of bytes that represent multibyte characters, +using encodings such as UTF-8 and others. + + Check every system call for an error return, unless you know you +wish to ignore errors. Include the system error text (from `perror' or +equivalent) in _every_ error message resulting from a failing system +call, as well as the name of the file if any and the name of the +utility. Just "cannot open foo.c" or "stat failed" is not sufficient. + + Check every call to `malloc' or `realloc' to see if it returned +zero. Check `realloc' even if you are making the block smaller; in a +system that rounds block sizes to a power of 2, `realloc' may get a +different block if you ask for less space. + + In Unix, `realloc' can destroy the storage block if it returns zero. +GNU `realloc' does not have this bug: if it fails, the original block +is unchanged. Feel free to assume the bug is fixed. If you wish to +run your program on Unix, and wish to avoid lossage in this case, you +can use the GNU `malloc'. + + You must expect `free' to alter the contents of the block that was +freed. Anything you want to fetch from the block, you must fetch before +calling `free'. + + If `malloc' fails in a noninteractive program, make that a fatal +error. In an interactive program (one that reads commands from the +user), it is better to abort the command and return to the command +reader loop. This allows the user to kill other processes to free up +virtual memory, and then try the command again. + + Use `getopt_long' to decode arguments, unless the argument syntax +makes this unreasonable. + + When static storage is to be written in during program execution, use +explicit C code to initialize it. Reserve C initialized declarations +for data that will not be changed. + + Try to avoid low-level interfaces to obscure Unix data structures +(such as file directories, utmp, or the layout of kernel memory), since +these are less likely to work compatibly. If you need to find all the +files in a directory, use `readdir' or some other high-level interface. +These are supported compatibly by GNU. + + The preferred signal handling facilities are the BSD variant of +`signal', and the POSIX `sigaction' function; the alternative USG +`signal' interface is an inferior design. + + Nowadays, using the POSIX signal functions may be the easiest way to +make a program portable. If you use `signal', then on GNU/Linux +systems running GNU libc version 1, you should include `bsd/signal.h' +instead of `signal.h', so as to get BSD behavior. It is up to you +whether to support systems where `signal' has only the USG behavior, or +give up on them. + + In error checks that detect "impossible" conditions, just abort. +There is usually no point in printing any message. These checks +indicate the existence of bugs. Whoever wants to fix the bugs will have +to read the source code and run a debugger. So explain the problem with +comments in the source. The relevant data will be in variables, which +are easy to examine with the debugger, so there is no point moving them +elsewhere. + + Do not use a count of errors as the exit status for a program. +_That does not work_, because exit status values are limited to 8 bits +(0 through 255). A single run of the program might have 256 errors; if +you try to return 256 as the exit status, the parent process will see 0 +as the status, and it will appear that the program succeeded. + + If you make temporary files, check the `TMPDIR' environment +variable; if that variable is defined, use the specified directory +instead of `/tmp'. + + In addition, be aware that there is a possible security problem when +creating temporary files in world-writable directories. In C, you can +avoid this problem by creating temporary files in this manner: + + fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0600); + +or by using the `mkstemps' function from libiberty. + + In bash, use `set -C' to avoid this problem. + + +File: standards.info, Node: Libraries, Next: Errors, Prev: Semantics, Up: Program Behavior + +4.2 Library Behavior +==================== + +Try to make library functions reentrant. If they need to do dynamic +storage allocation, at least try to avoid any nonreentrancy aside from +that of `malloc' itself. + + Here are certain name conventions for libraries, to avoid name +conflicts. + + Choose a name prefix for the library, more than two characters long. +All external function and variable names should start with this prefix. +In addition, there should only be one of these in any given library +member. This usually means putting each one in a separate source file. + + An exception can be made when two external symbols are always used +together, so that no reasonable program could use one without the +other; then they can both go in the same file. + + External symbols that are not documented entry points for the user +should have names beginning with `_'. The `_' should be followed by +the chosen name prefix for the library, to prevent collisions with +other libraries. These can go in the same files with user entry points +if you like. + + Static functions and variables can be used as you like and need not +fit any naming convention. + + +File: standards.info, Node: Errors, Next: User Interfaces, Prev: Libraries, Up: Program Behavior + +4.3 Formatting Error Messages +============================= + +Error messages from compilers should look like this: + + SOURCE-FILE-NAME:LINENO: MESSAGE + +If you want to mention the column number, use this format: + + SOURCE-FILE-NAME:LINENO:COLUMN: MESSAGE + +Line numbers should start from 1 at the beginning of the file, and +column numbers should start from 1 at the beginning of the line. (Both +of these conventions are chosen for compatibility.) Calculate column +numbers assuming that space and all ASCII printing characters have +equal width, and assuming tab stops every 8 columns. + + Error messages from other noninteractive programs should look like +this: + + PROGRAM:SOURCE-FILE-NAME:LINENO: MESSAGE + +when there is an appropriate source file, or like this: + + PROGRAM: MESSAGE + +when there is no relevant source file. + + If you want to mention the column number, use this format: + + PROGRAM:SOURCE-FILE-NAME:LINENO:COLUMN: MESSAGE + + In an interactive program (one that is reading commands from a +terminal), it is better not to include the program name in an error +message. The place to indicate which program is running is in the +prompt or with the screen layout. (When the same program runs with +input from a source other than a terminal, it is not interactive and +would do best to print error messages using the noninteractive style.) + + The string MESSAGE should not begin with a capital letter when it +follows a program name and/or file name. Also, it should not end with +a period. + + Error messages from interactive programs, and other messages such as +usage messages, should start with a capital letter. But they should not +end with a period. + + +File: standards.info, Node: User Interfaces, Next: Graphical Interfaces, Prev: Errors, Up: Program Behavior + +4.4 Standards for Interfaces Generally +====================================== + +Please don't make the behavior of a utility depend on the name used to +invoke it. It is useful sometimes to make a link to a utility with a +different name, and that should not change what it does. + + Instead, use a run time option or a compilation switch or both to +select among the alternate behaviors. + + Likewise, please don't make the behavior of the program depend on the +type of output device it is used with. Device independence is an +important principle of the system's design; do not compromise it merely +to save someone from typing an option now and then. (Variation in error +message syntax when using a terminal is ok, because that is a side issue +that people do not depend on.) + + If you think one behavior is most useful when the output is to a +terminal, and another is most useful when the output is a file or a +pipe, then it is usually best to make the default behavior the one that +is useful with output to a terminal, and have an option for the other +behavior. + + Compatibility requires certain programs to depend on the type of +output device. It would be disastrous if `ls' or `sh' did not do so in +the way all users expect. In some of these cases, we supplement the +program with a preferred alternate version that does not depend on the +output device type. For example, we provide a `dir' program much like +`ls' except that its default output format is always multi-column +format. + + +File: standards.info, Node: Graphical Interfaces, Next: Command-Line Interfaces, Prev: User Interfaces, Up: Program Behavior + +4.5 Standards for Graphical Interfaces +====================================== + +When you write a program that provides a graphical user interface, +please make it work with X Windows and the GTK toolkit unless the +functionality specifically requires some alternative (for example, +"displaying jpeg images while in console mode"). + + In addition, please provide a command-line interface to control the +functionality. (In many cases, the graphical user interface can be a +separate program which invokes the command-line program.) This is so +that the same jobs can be done from scripts. + + Please also consider providing a CORBA interface (for use from +GNOME), a library interface (for use from C), and perhaps a +keyboard-driven console interface (for use by users from console mode). +Once you are doing the work to provide the functionality and the +graphical interface, these won't be much extra work. + + +File: standards.info, Node: Command-Line Interfaces, Next: Option Table, Prev: Graphical Interfaces, Up: Program Behavior + +4.6 Standards for Command Line Interfaces +========================================= + +It is a good idea to follow the POSIX guidelines for the command-line +options of a program. The easiest way to do this is to use `getopt' to +parse them. Note that the GNU version of `getopt' will normally permit +options anywhere among the arguments unless the special argument `--' +is used. This is not what POSIX specifies; it is a GNU extension. + + Please define long-named options that are equivalent to the +single-letter Unix-style options. We hope to make GNU more user +friendly this way. This is easy to do with the GNU function +`getopt_long'. + + One of the advantages of long-named options is that they can be +consistent from program to program. For example, users should be able +to expect the "verbose" option of any GNU program which has one, to be +spelled precisely `--verbose'. To achieve this uniformity, look at the +table of common long-option names when you choose the option names for +your program (*note Option Table::). + + It is usually a good idea for file names given as ordinary arguments +to be input files only; any output files would be specified using +options (preferably `-o' or `--output'). Even if you allow an output +file name as an ordinary argument for compatibility, try to provide an +option as another way to specify it. This will lead to more consistency +among GNU utilities, and fewer idiosyncracies for users to remember. + + All programs should support two standard options: `--version' and +`--help'. + +`--version' + This option should direct the program to print information about + its name, version, origin and legal status, all on standard + output, and then exit successfully. Other options and arguments + should be ignored once this is seen, and the program should not + perform its normal function. + + The first line is meant to be easy for a program to parse; the + version number proper starts after the last space. In addition, + it contains the canonical name for this program, in this format: + + GNU Emacs 19.30 + + The program's name should be a constant string; _don't_ compute it + from `argv[0]'. The idea is to state the standard or canonical + name for the program, not its file name. There are other ways to + find out the precise file name where a command is found in `PATH'. + + If the program is a subsidiary part of a larger package, mention + the package name in parentheses, like this: + + emacsserver (GNU Emacs) 19.30 + + If the package has a version number which is different from this + program's version number, you can mention the package version + number just before the close-parenthesis. + + If you *need* to mention the version numbers of libraries which + are distributed separately from the package which contains this + program, you can do so by printing an additional line of version + info for each library you want to mention. Use the same format + for these lines as for the first line. + + Please do not mention all of the libraries that the program uses + "just for completeness"--that would produce a lot of unhelpful + clutter. Please mention library version numbers only if you find + in practice that they are very important to you in debugging. + + The following line, after the version number line or lines, should + be a copyright notice. If more than one copyright notice is + called for, put each on a separate line. + + Next should follow a brief statement that the program is free + software, and that users are free to copy and change it on certain + conditions. If the program is covered by the GNU GPL, say so + here. Also mention that there is no warranty, to the extent + permitted by law. + + It is ok to finish the output with a list of the major authors of + the program, as a way of giving credit. + + Here's an example of output that follows these rules: + + GNU Emacs 19.34.5 + Copyright (C) 1996 Free Software Foundation, Inc. + GNU Emacs comes with NO WARRANTY, + to the extent permitted by law. + You may redistribute copies of GNU Emacs + under the terms of the GNU General Public License. + For more information about these matters, + see the files named COPYING. + + You should adapt this to your program, of course, filling in the + proper year, copyright holder, name of program, and the references + to distribution terms, and changing the rest of the wording as + necessary. + + This copyright notice only needs to mention the most recent year in + which changes were made--there's no need to list the years for + previous versions' changes. You don't have to mention the name of + the program in these notices, if that is inconvenient, since it + appeared in the first line. + + Translations of the above lines must preserve the validity of the + copyright notices (*note Internationalization::). If the + translation's character set supports it, the `(C)' should be + replaced with the copyright symbol, as follows: + + (the official copyright symbol, which is the letter C in a circle); + + Write the word "Copyright" exactly like that, in English. Do not + translate it into another language. International treaties + recognize the English word "Copyright"; translations into other + languages do not have legal significance. + +`--help' + This option should output brief documentation for how to invoke the + program, on standard output, then exit successfully. Other + options and arguments should be ignored once this is seen, and the + program should not perform its normal function. + + Near the end of the `--help' option's output there should be a line + that says where to mail bug reports. It should have this format: + + Report bugs to MAILING-ADDRESS. + + +File: standards.info, Node: Option Table, Next: Memory Usage, Prev: Command-Line Interfaces, Up: Program Behavior + +4.7 Table of Long Options +========================= + +Here is a table of long options used by GNU programs. It is surely +incomplete, but we aim to list all the options that a new program might +want to be compatible with. If you use names not already in the table, +please send <bug-standards@gnu.org> a list of them, with their +meanings, so we can update the table. + +`after-date' + `-N' in `tar'. + +`all' + `-a' in `du', `ls', `nm', `stty', `uname', and `unexpand'. + +`all-text' + `-a' in `diff'. + +`almost-all' + `-A' in `ls'. + +`append' + `-a' in `etags', `tee', `time'; `-r' in `tar'. + +`archive' + `-a' in `cp'. + +`archive-name' + `-n' in `shar'. + +`arglength' + `-l' in `m4'. + +`ascii' + `-a' in `diff'. + +`assign' + `-v' in `gawk'. + +`assume-new' + `-W' in Make. + +`assume-old' + `-o' in Make. + +`auto-check' + `-a' in `recode'. + +`auto-pager' + `-a' in `wdiff'. + +`auto-reference' + `-A' in `ptx'. + +`avoid-wraps' + `-n' in `wdiff'. + +`background' + For server programs, run in the background. + +`backward-search' + `-B' in `ctags'. + +`basename' + `-f' in `shar'. + +`batch' + Used in GDB. + +`baud' + Used in GDB. + +`before' + `-b' in `tac'. + +`binary' + `-b' in `cpio' and `diff'. + +`bits-per-code' + `-b' in `shar'. + +`block-size' + Used in `cpio' and `tar'. + +`blocks' + `-b' in `head' and `tail'. + +`break-file' + `-b' in `ptx'. + +`brief' + Used in various programs to make output shorter. + +`bytes' + `-c' in `head', `split', and `tail'. + +`c++' + `-C' in `etags'. + +`catenate' + `-A' in `tar'. + +`cd' + Used in various programs to specify the directory to use. + +`changes' + `-c' in `chgrp' and `chown'. + +`classify' + `-F' in `ls'. + +`colons' + `-c' in `recode'. + +`command' + `-c' in `su'; `-x' in GDB. + +`compare' + `-d' in `tar'. + +`compat' + Used in `gawk'. + +`compress' + `-Z' in `tar' and `shar'. + +`concatenate' + `-A' in `tar'. + +`confirmation' + `-w' in `tar'. + +`context' + Used in `diff'. + +`copyleft' + `-W copyleft' in `gawk'. + +`copyright' + `-C' in `ptx', `recode', and `wdiff'; `-W copyright' in `gawk'. + +`core' + Used in GDB. + +`count' + `-q' in `who'. + +`count-links' + `-l' in `du'. + +`create' + Used in `tar' and `cpio'. + +`cut-mark' + `-c' in `shar'. + +`cxref' + `-x' in `ctags'. + +`date' + `-d' in `touch'. + +`debug' + `-d' in Make and `m4'; `-t' in Bison. + +`define' + `-D' in `m4'. + +`defines' + `-d' in Bison and `ctags'. + +`delete' + `-D' in `tar'. + +`dereference' + `-L' in `chgrp', `chown', `cpio', `du', `ls', and `tar'. + +`dereference-args' + `-D' in `du'. + +`device' + Specify an I/O device (special file name). + +`diacritics' + `-d' in `recode'. + +`dictionary-order' + `-d' in `look'. + +`diff' + `-d' in `tar'. + +`digits' + `-n' in `csplit'. + +`directory' + Specify the directory to use, in various programs. In `ls', it + means to show directories themselves rather than their contents. + In `rm' and `ln', it means to not treat links to directories + specially. + +`discard-all' + `-x' in `strip'. + +`discard-locals' + `-X' in `strip'. + +`dry-run' + `-n' in Make. + +`ed' + `-e' in `diff'. + +`elide-empty-files' + `-z' in `csplit'. + +`end-delete' + `-x' in `wdiff'. + +`end-insert' + `-z' in `wdiff'. + +`entire-new-file' + `-N' in `diff'. + +`environment-overrides' + `-e' in Make. + +`eof' + `-e' in `xargs'. + +`epoch' + Used in GDB. + +`error-limit' + Used in `makeinfo'. + +`error-output' + `-o' in `m4'. + +`escape' + `-b' in `ls'. + +`exclude-from' + `-X' in `tar'. + +`exec' + Used in GDB. + +`exit' + `-x' in `xargs'. + +`exit-0' + `-e' in `unshar'. + +`expand-tabs' + `-t' in `diff'. + +`expression' + `-e' in `sed'. + +`extern-only' + `-g' in `nm'. + +`extract' + `-i' in `cpio'; `-x' in `tar'. + +`faces' + `-f' in `finger'. + +`fast' + `-f' in `su'. + +`fatal-warnings' + `-E' in `m4'. + +`file' + `-f' in `info', `gawk', Make, `mt', and `tar'; `-n' in `sed'; `-r' + in `touch'. + +`field-separator' + `-F' in `gawk'. + +`file-prefix' + `-b' in Bison. + +`file-type' + `-F' in `ls'. + +`files-from' + `-T' in `tar'. + +`fill-column' + Used in `makeinfo'. + +`flag-truncation' + `-F' in `ptx'. + +`fixed-output-files' + `-y' in Bison. + +`follow' + `-f' in `tail'. + +`footnote-style' + Used in `makeinfo'. + +`force' + `-f' in `cp', `ln', `mv', and `rm'. + +`force-prefix' + `-F' in `shar'. + +`foreground' + For server programs, run in the foreground; in other words, don't + do anything special to run the server in the background. + +`format' + Used in `ls', `time', and `ptx'. + +`freeze-state' + `-F' in `m4'. + +`fullname' + Used in GDB. + +`gap-size' + `-g' in `ptx'. + +`get' + `-x' in `tar'. + +`graphic' + `-i' in `ul'. + +`graphics' + `-g' in `recode'. + +`group' + `-g' in `install'. + +`gzip' + `-z' in `tar' and `shar'. + +`hashsize' + `-H' in `m4'. + +`header' + `-h' in `objdump' and `recode' + +`heading' + `-H' in `who'. + +`help' + Used to ask for brief usage information. + +`here-delimiter' + `-d' in `shar'. + +`hide-control-chars' + `-q' in `ls'. + +`html' + In `makeinfo', output HTML. + +`idle' + `-u' in `who'. + +`ifdef' + `-D' in `diff'. + +`ignore' + `-I' in `ls'; `-x' in `recode'. + +`ignore-all-space' + `-w' in `diff'. + +`ignore-backups' + `-B' in `ls'. + +`ignore-blank-lines' + `-B' in `diff'. + +`ignore-case' + `-f' in `look' and `ptx'; `-i' in `diff' and `wdiff'. + +`ignore-errors' + `-i' in Make. + +`ignore-file' + `-i' in `ptx'. + +`ignore-indentation' + `-I' in `etags'. + +`ignore-init-file' + `-f' in Oleo. + +`ignore-interrupts' + `-i' in `tee'. + +`ignore-matching-lines' + `-I' in `diff'. + +`ignore-space-change' + `-b' in `diff'. + +`ignore-zeros' + `-i' in `tar'. + +`include' + `-i' in `etags'; `-I' in `m4'. + +`include-dir' + `-I' in Make. + +`incremental' + `-G' in `tar'. + +`info' + `-i', `-l', and `-m' in Finger. + +`init-file' + In some programs, specify the name of the file to read as the + user's init file. + +`initial' + `-i' in `expand'. + +`initial-tab' + `-T' in `diff'. + +`inode' + `-i' in `ls'. + +`interactive' + `-i' in `cp', `ln', `mv', `rm'; `-e' in `m4'; `-p' in `xargs'; + `-w' in `tar'. + +`intermix-type' + `-p' in `shar'. + +`iso-8601' + Used in `date' + +`jobs' + `-j' in Make. + +`just-print' + `-n' in Make. + +`keep-going' + `-k' in Make. + +`keep-files' + `-k' in `csplit'. + +`kilobytes' + `-k' in `du' and `ls'. + +`language' + `-l' in `etags'. + +`less-mode' + `-l' in `wdiff'. + +`level-for-gzip' + `-g' in `shar'. + +`line-bytes' + `-C' in `split'. + +`lines' + Used in `split', `head', and `tail'. + +`link' + `-l' in `cpio'. + +`lint' +`lint-old' + Used in `gawk'. + +`list' + `-t' in `cpio'; `-l' in `recode'. + +`list' + `-t' in `tar'. + +`literal' + `-N' in `ls'. + +`load-average' + `-l' in Make. + +`login' + Used in `su'. + +`machine' + No listing of which programs already use this; someone should + check to see if any actually do, and tell <gnu@gnu.org>. + +`macro-name' + `-M' in `ptx'. + +`mail' + `-m' in `hello' and `uname'. + +`make-directories' + `-d' in `cpio'. + +`makefile' + `-f' in Make. + +`mapped' + Used in GDB. + +`max-args' + `-n' in `xargs'. + +`max-chars' + `-n' in `xargs'. + +`max-lines' + `-l' in `xargs'. + +`max-load' + `-l' in Make. + +`max-procs' + `-P' in `xargs'. + +`mesg' + `-T' in `who'. + +`message' + `-T' in `who'. + +`minimal' + `-d' in `diff'. + +`mixed-uuencode' + `-M' in `shar'. + +`mode' + `-m' in `install', `mkdir', and `mkfifo'. + +`modification-time' + `-m' in `tar'. + +`multi-volume' + `-M' in `tar'. + +`name-prefix' + `-a' in Bison. + +`nesting-limit' + `-L' in `m4'. + +`net-headers' + `-a' in `shar'. + +`new-file' + `-W' in Make. + +`no-builtin-rules' + `-r' in Make. + +`no-character-count' + `-w' in `shar'. + +`no-check-existing' + `-x' in `shar'. + +`no-common' + `-3' in `wdiff'. + +`no-create' + `-c' in `touch'. + +`no-defines' + `-D' in `etags'. + +`no-deleted' + `-1' in `wdiff'. + +`no-dereference' + `-d' in `cp'. + +`no-inserted' + `-2' in `wdiff'. + +`no-keep-going' + `-S' in Make. + +`no-lines' + `-l' in Bison. + +`no-piping' + `-P' in `shar'. + +`no-prof' + `-e' in `gprof'. + +`no-regex' + `-R' in `etags'. + +`no-sort' + `-p' in `nm'. + +`no-split' + Used in `makeinfo'. + +`no-static' + `-a' in `gprof'. + +`no-time' + `-E' in `gprof'. + +`no-timestamp' + `-m' in `shar'. + +`no-validate' + Used in `makeinfo'. + +`no-wait' + Used in `emacsclient'. + +`no-warn' + Used in various programs to inhibit warnings. + +`node' + `-n' in `info'. + +`nodename' + `-n' in `uname'. + +`nonmatching' + `-f' in `cpio'. + +`nstuff' + `-n' in `objdump'. + +`null' + `-0' in `xargs'. + +`number' + `-n' in `cat'. + +`number-nonblank' + `-b' in `cat'. + +`numeric-sort' + `-n' in `nm'. + +`numeric-uid-gid' + `-n' in `cpio' and `ls'. + +`nx' + Used in GDB. + +`old-archive' + `-o' in `tar'. + +`old-file' + `-o' in Make. + +`one-file-system' + `-l' in `tar', `cp', and `du'. + +`only-file' + `-o' in `ptx'. + +`only-prof' + `-f' in `gprof'. + +`only-time' + `-F' in `gprof'. + +`options' + `-o' in `getopt', `fdlist', `fdmount', `fdmountd', and `fdumount'. + +`output' + In various programs, specify the output file name. + +`output-prefix' + `-o' in `shar'. + +`override' + `-o' in `rm'. + +`overwrite' + `-c' in `unshar'. + +`owner' + `-o' in `install'. + +`paginate' + `-l' in `diff'. + +`paragraph-indent' + Used in `makeinfo'. + +`parents' + `-p' in `mkdir' and `rmdir'. + +`pass-all' + `-p' in `ul'. + +`pass-through' + `-p' in `cpio'. + +`port' + `-P' in `finger'. + +`portability' + `-c' in `cpio' and `tar'. + +`posix' + Used in `gawk'. + +`prefix-builtins' + `-P' in `m4'. + +`prefix' + `-f' in `csplit'. + +`preserve' + Used in `tar' and `cp'. + +`preserve-environment' + `-p' in `su'. + +`preserve-modification-time' + `-m' in `cpio'. + +`preserve-order' + `-s' in `tar'. + +`preserve-permissions' + `-p' in `tar'. + +`print' + `-l' in `diff'. + +`print-chars' + `-L' in `cmp'. + +`print-data-base' + `-p' in Make. + +`print-directory' + `-w' in Make. + +`print-file-name' + `-o' in `nm'. + +`print-symdefs' + `-s' in `nm'. + +`printer' + `-p' in `wdiff'. + +`prompt' + `-p' in `ed'. + +`proxy' + Specify an HTTP proxy. + +`query-user' + `-X' in `shar'. + +`question' + `-q' in Make. + +`quiet' + Used in many programs to inhibit the usual output. *Note_* every + program accepting `--quiet' should accept `--silent' as a synonym. + +`quiet-unshar' + `-Q' in `shar' + +`quote-name' + `-Q' in `ls'. + +`rcs' + `-n' in `diff'. + +`re-interval' + Used in `gawk'. + +`read-full-blocks' + `-B' in `tar'. + +`readnow' + Used in GDB. + +`recon' + `-n' in Make. + +`record-number' + `-R' in `tar'. + +`recursive' + Used in `chgrp', `chown', `cp', `ls', `diff', and `rm'. + +`reference-limit' + Used in `makeinfo'. + +`references' + `-r' in `ptx'. + +`regex' + `-r' in `tac' and `etags'. + +`release' + `-r' in `uname'. + +`reload-state' + `-R' in `m4'. + +`relocation' + `-r' in `objdump'. + +`rename' + `-r' in `cpio'. + +`replace' + `-i' in `xargs'. + +`report-identical-files' + `-s' in `diff'. + +`reset-access-time' + `-a' in `cpio'. + +`reverse' + `-r' in `ls' and `nm'. + +`reversed-ed' + `-f' in `diff'. + +`right-side-defs' + `-R' in `ptx'. + +`same-order' + `-s' in `tar'. + +`same-permissions' + `-p' in `tar'. + +`save' + `-g' in `stty'. + +`se' + Used in GDB. + +`sentence-regexp' + `-S' in `ptx'. + +`separate-dirs' + `-S' in `du'. + +`separator' + `-s' in `tac'. + +`sequence' + Used by `recode' to chose files or pipes for sequencing passes. + +`shell' + `-s' in `su'. + +`show-all' + `-A' in `cat'. + +`show-c-function' + `-p' in `diff'. + +`show-ends' + `-E' in `cat'. + +`show-function-line' + `-F' in `diff'. + +`show-tabs' + `-T' in `cat'. + +`silent' + Used in many programs to inhibit the usual output. *Note_* every + program accepting `--silent' should accept `--quiet' as a synonym. + +`size' + `-s' in `ls'. + +`socket' + Specify a file descriptor for a network server to use for its + socket, instead of opening and binding a new socket. This + provides a way to run, in a nonpriveledged process, a server that + normally needs a reserved port number. + +`sort' + Used in `ls'. + +`source' + `-W source' in `gawk'. + +`sparse' + `-S' in `tar'. + +`speed-large-files' + `-H' in `diff'. + +`split-at' + `-E' in `unshar'. + +`split-size-limit' + `-L' in `shar'. + +`squeeze-blank' + `-s' in `cat'. + +`start-delete' + `-w' in `wdiff'. + +`start-insert' + `-y' in `wdiff'. + +`starting-file' + Used in `tar' and `diff' to specify which file within a directory + to start processing with. + +`statistics' + `-s' in `wdiff'. + +`stdin-file-list' + `-S' in `shar'. + +`stop' + `-S' in Make. + +`strict' + `-s' in `recode'. + +`strip' + `-s' in `install'. + +`strip-all' + `-s' in `strip'. + +`strip-debug' + `-S' in `strip'. + +`submitter' + `-s' in `shar'. + +`suffix' + `-S' in `cp', `ln', `mv'. + +`suffix-format' + `-b' in `csplit'. + +`sum' + `-s' in `gprof'. + +`summarize' + `-s' in `du'. + +`symbolic' + `-s' in `ln'. + +`symbols' + Used in GDB and `objdump'. + +`synclines' + `-s' in `m4'. + +`sysname' + `-s' in `uname'. + +`tabs' + `-t' in `expand' and `unexpand'. + +`tabsize' + `-T' in `ls'. + +`terminal' + `-T' in `tput' and `ul'. `-t' in `wdiff'. + +`text' + `-a' in `diff'. + +`text-files' + `-T' in `shar'. + +`time' + Used in `ls' and `touch'. + +`timeout' + Specify how long to wait before giving up on some operation. + +`to-stdout' + `-O' in `tar'. + +`total' + `-c' in `du'. + +`touch' + `-t' in Make, `ranlib', and `recode'. + +`trace' + `-t' in `m4'. + +`traditional' + `-t' in `hello'; `-W traditional' in `gawk'; `-G' in `ed', `m4', + and `ptx'. + +`tty' + Used in GDB. + +`typedefs' + `-t' in `ctags'. + +`typedefs-and-c++' + `-T' in `ctags'. + +`typeset-mode' + `-t' in `ptx'. + +`uncompress' + `-z' in `tar'. + +`unconditional' + `-u' in `cpio'. + +`undefine' + `-U' in `m4'. + +`undefined-only' + `-u' in `nm'. + +`update' + `-u' in `cp', `ctags', `mv', `tar'. + +`usage' + Used in `gawk'; same as `--help'. + +`uuencode' + `-B' in `shar'. + +`vanilla-operation' + `-V' in `shar'. + +`verbose' + Print more information about progress. Many programs support this. + +`verify' + `-W' in `tar'. + +`version' + Print the version number. + +`version-control' + `-V' in `cp', `ln', `mv'. + +`vgrind' + `-v' in `ctags'. + +`volume' + `-V' in `tar'. + +`what-if' + `-W' in Make. + +`whole-size-limit' + `-l' in `shar'. + +`width' + `-w' in `ls' and `ptx'. + +`word-regexp' + `-W' in `ptx'. + +`writable' + `-T' in `who'. + +`zeros' + `-z' in `gprof'. + + +File: standards.info, Node: Memory Usage, Next: File Usage, Prev: Option Table, Up: Program Behavior + +4.8 Memory Usage +================ + +If a program typically uses just a few meg of memory, don't bother +making any effort to reduce memory usage. For example, if it is +impractical for other reasons to operate on files more than a few meg +long, it is reasonable to read entire input files into core to operate +on them. + + However, for programs such as `cat' or `tail', that can usefully +operate on very large files, it is important to avoid using a technique +that would artificially limit the size of files it can handle. If a +program works by lines and could be applied to arbitrary user-supplied +input files, it should keep only a line in memory, because this is not +very hard and users will want to be able to operate on input files that +are bigger than will fit in core all at once. + + If your program creates complicated data structures, just make them +in core and give a fatal error if `malloc' returns zero. + + +File: standards.info, Node: File Usage, Prev: Memory Usage, Up: Program Behavior + +4.9 File Usage +============== + +Programs should be prepared to operate when `/usr' and `/etc' are +read-only file systems. Thus, if the program manages log files, lock +files, backup files, score files, or any other files which are modified +for internal purposes, these files should not be stored in `/usr' or +`/etc'. + + There are two exceptions. `/etc' is used to store system +configuration information; it is reasonable for a program to modify +files in `/etc' when its job is to update the system configuration. +Also, if the user explicitly asks to modify one file in a directory, it +is reasonable for the program to store other files in the same +directory. + + +File: standards.info, Node: Writing C, Next: Documentation, Prev: Program Behavior, Up: Top + +5 Making The Best Use of C +************************** + +This node provides advice on how best to use the C language when +writing GNU software. + +* Menu: + +* Formatting:: Formatting Your Source Code +* Comments:: Commenting Your Work +* Syntactic Conventions:: Clean Use of C Constructs +* Names:: Naming Variables, Functions, and Files +* System Portability:: Portability between different operating systems +* CPU Portability:: Supporting the range of CPU types +* System Functions:: Portability and ``standard'' library functions +* Internationalization:: Techniques for internationalization +* Mmap:: How you can safely use `mmap'. + + +File: standards.info, Node: Formatting, Next: Comments, Up: Writing C + +5.1 Formatting Your Source Code +=============================== + +It is important to put the open-brace that starts the body of a C +function in column zero, and avoid putting any other open-brace or +open-parenthesis or open-bracket in column zero. Several tools look +for open-braces in column zero to find the beginnings of C functions. +These tools will not work on code not formatted that way. + + It is also important for function definitions to start the name of +the function in column zero. This helps people to search for function +definitions, and may also help certain tools recognize them. Thus, the +proper format is this: + + static char * + concat (s1, s2) /* Name starts in column zero here */ + char *s1, *s2; + { /* Open brace in column zero here */ + ... + } + +or, if you want to use Standard C syntax, format the definition like +this: + + static char * + concat (char *s1, char *s2) + { + ... + } + + In Standard C, if the arguments don't fit nicely on one line, split +it like this: + + int + lots_of_args (int an_integer, long a_long, short a_short, + double a_double, float a_float) + ... + + The rest of this section gives our recommendations for other aspects +of C formatting style, which is also the default style of the `indent' +program in version 1.2 and newer. It corresponds to the options + + -nbad -bap -nbc -bbo -bl -bli2 -bls -ncdb -nce -cp1 -cs -di2 + -ndj -nfc1 -nfca -hnl -i2 -ip5 -lp -pcs -psl -nsc -nsob + + We don't think of these recommendations as requirements, because it +causes no problems for users if two different programs have different +formatting styles. + + But whatever style you use, please use it consistently, since a +mixture of styles within one program tends to look ugly. If you are +contributing changes to an existing program, please follow the style of +that program. + + For the body of the function, our recommended style looks like this: + + if (x < foo (y, z)) + haha = bar[4] + 5; + else + { + while (z) + { + haha += foo (z, z); + z--; + } + return ++x + bar (); + } + + We find it easier to read a program when it has spaces before the +open-parentheses and after the commas. Especially after the commas. + + When you split an expression into multiple lines, split it before an +operator, not after one. Here is the right way: + + if (foo_this_is_long && bar > win (x, y, z) + && remaining_condition) + + Try to avoid having two operators of different precedence at the same +level of indentation. For example, don't write this: + + mode = (inmode[j] == VOIDmode + || GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j]) + ? outmode[j] : inmode[j]); + + Instead, use extra parentheses so that the indentation shows the +nesting: + + mode = ((inmode[j] == VOIDmode + || (GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j]))) + ? outmode[j] : inmode[j]); + + Insert extra parentheses so that Emacs will indent the code properly. +For example, the following indentation looks nice if you do it by hand, + + v = rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000 + + rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000; + +but Emacs would alter it. Adding a set of parentheses produces +something that looks equally nice, and which Emacs will preserve: + + v = (rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000 + + rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000); + + Format do-while statements like this: + + do + { + a = foo (a); + } + while (a > 0); + + Please use formfeed characters (control-L) to divide the program into +pages at logical places (but not within a function). It does not matter +just how long the pages are, since they do not have to fit on a printed +page. The formfeeds should appear alone on lines by themselves. + + +File: standards.info, Node: Comments, Next: Syntactic Conventions, Prev: Formatting, Up: Writing C + +5.2 Commenting Your Work +======================== + +Every program should start with a comment saying briefly what it is for. +Example: `fmt - filter for simple filling of text'. + + Please write the comments in a GNU program in English, because +English is the one language that nearly all programmers in all +countries can read. If you do not write English well, please write +comments in English as well as you can, then ask other people to help +rewrite them. If you can't write comments in English, please find +someone to work with you and translate your comments into English. + + Please put a comment on each function saying what the function does, +what sorts of arguments it gets, and what the possible values of +arguments mean and are used for. It is not necessary to duplicate in +words the meaning of the C argument declarations, if a C type is being +used in its customary fashion. If there is anything nonstandard about +its use (such as an argument of type `char *' which is really the +address of the second character of a string, not the first), or any +possible values that would not work the way one would expect (such as, +that strings containing newlines are not guaranteed to work), be sure +to say so. + + Also explain the significance of the return value, if there is one. + + Please put two spaces after the end of a sentence in your comments, +so that the Emacs sentence commands will work. Also, please write +complete sentences and capitalize the first word. If a lower-case +identifier comes at the beginning of a sentence, don't capitalize it! +Changing the spelling makes it a different identifier. If you don't +like starting a sentence with a lower case letter, write the sentence +differently (e.g., "The identifier lower-case is ..."). + + The comment on a function is much clearer if you use the argument +names to speak about the argument values. The variable name itself +should be lower case, but write it in upper case when you are speaking +about the value rather than the variable itself. Thus, "the inode +number NODE_NUM" rather than "an inode". + + There is usually no purpose in restating the name of the function in +the comment before it, because the reader can see that for himself. +There might be an exception when the comment is so long that the +function itself would be off the bottom of the screen. + + There should be a comment on each static variable as well, like this: + + /* Nonzero means truncate lines in the display; + zero means continue them. */ + int truncate_lines; + + Every `#endif' should have a comment, except in the case of short +conditionals (just a few lines) that are not nested. The comment should +state the condition of the conditional that is ending, _including its +sense_. `#else' should have a comment describing the condition _and +sense_ of the code that follows. For example: + + #ifdef foo + ... + #else /* not foo */ + ... + #endif /* not foo */ + #ifdef foo + ... + #endif /* foo */ + +but, by contrast, write the comments this way for a `#ifndef': + + #ifndef foo + ... + #else /* foo */ + ... + #endif /* foo */ + #ifndef foo + ... + #endif /* not foo */ + + +File: standards.info, Node: Syntactic Conventions, Next: Names, Prev: Comments, Up: Writing C + +5.3 Clean Use of C Constructs +============================= + +Please explicitly declare the types of all objects. For example, you +should explicitly declare all arguments to functions, and you should +declare functions to return `int' rather than omitting the `int'. + + Some programmers like to use the GCC `-Wall' option, and change the +code whenever it issues a warning. If you want to do this, then do. +Other programmers prefer not to use `-Wall', because it gives warnings +for valid and legitimate code which they do not want to change. If you +want to do this, then do. The compiler should be your servant, not +your master. + + Declarations of external functions and functions to appear later in +the source file should all go in one place near the beginning of the +file (somewhere before the first function definition in the file), or +else should go in a header file. Don't put `extern' declarations inside +functions. + + It used to be common practice to use the same local variables (with +names like `tem') over and over for different values within one +function. Instead of doing this, it is better declare a separate local +variable for each distinct purpose, and give it a name which is +meaningful. This not only makes programs easier to understand, it also +facilitates optimization by good compilers. You can also move the +declaration of each local variable into the smallest scope that includes +all its uses. This makes the program even cleaner. + + Don't use local variables or parameters that shadow global +identifiers. + + Don't declare multiple variables in one declaration that spans lines. +Start a new declaration on each line, instead. For example, instead of +this: + + int foo, + bar; + +write either this: + + int foo, bar; + +or this: + + int foo; + int bar; + +(If they are global variables, each should have a comment preceding it +anyway.) + + When you have an `if'-`else' statement nested in another `if' +statement, always put braces around the `if'-`else'. Thus, never write +like this: + + if (foo) + if (bar) + win (); + else + lose (); + +always like this: + + if (foo) + { + if (bar) + win (); + else + lose (); + } + + If you have an `if' statement nested inside of an `else' statement, +either write `else if' on one line, like this, + + if (foo) + ... + else if (bar) + ... + +with its `then'-part indented like the preceding `then'-part, or write +the nested `if' within braces like this: + + if (foo) + ... + else + { + if (bar) + ... + } + + Don't declare both a structure tag and variables or typedefs in the +same declaration. Instead, declare the structure tag separately and +then use it to declare the variables or typedefs. + + Try to avoid assignments inside `if'-conditions. For example, don't +write this: + + if ((foo = (char *) malloc (sizeof *foo)) == 0) + fatal ("virtual memory exhausted"); + +instead, write this: + + foo = (char *) malloc (sizeof *foo); + if (foo == 0) + fatal ("virtual memory exhausted"); + + Don't make the program ugly to placate `lint'. Please don't insert +any casts to `void'. Zero without a cast is perfectly fine as a null +pointer constant, except when calling a varargs function. + + +File: standards.info, Node: Names, Next: System Portability, Prev: Syntactic Conventions, Up: Writing C + +5.4 Naming Variables, Functions, and Files +========================================== + +The names of global variables and functions in a program serve as +comments of a sort. So don't choose terse names--instead, look for +names that give useful information about the meaning of the variable or +function. In a GNU program, names should be English, like other +comments. + + Local variable names can be shorter, because they are used only +within one context, where (presumably) comments explain their purpose. + + Try to limit your use of abbreviations in symbol names. It is ok to +make a few abbreviations, explain what they mean, and then use them +frequently, but don't use lots of obscure abbreviations. + + Please use underscores to separate words in a name, so that the Emacs +word commands can be useful within them. Stick to lower case; reserve +upper case for macros and `enum' constants, and for name-prefixes that +follow a uniform convention. + + For example, you should use names like `ignore_space_change_flag'; +don't use names like `iCantReadThis'. + + Variables that indicate whether command-line options have been +specified should be named after the meaning of the option, not after +the option-letter. A comment should state both the exact meaning of +the option and its letter. For example, + + /* Ignore changes in horizontal whitespace (-b). */ + int ignore_space_change_flag; + + When you want to define names with constant integer values, use +`enum' rather than `#define'. GDB knows about enumeration constants. + + You might want to make sure that none of the file names would +conflict the files were loaded onto an MS-DOS file system which +shortens the names. You can use the program `doschk' to test for this. + + Some GNU programs were designed to limit themselves to file names of +14 characters or less, to avoid file name conflicts if they are read +into older System V systems. Please preserve this feature in the +existing GNU programs that have it, but there is no need to do this in +new GNU programs. `doschk' also reports file names longer than 14 +characters. + + +File: standards.info, Node: System Portability, Next: CPU Portability, Prev: Names, Up: Writing C + +5.5 Portability between System Types +==================================== + +In the Unix world, "portability" refers to porting to different Unix +versions. For a GNU program, this kind of portability is desirable, but +not paramount. + + The primary purpose of GNU software is to run on top of the GNU +kernel, compiled with the GNU C compiler, on various types of CPU. So +the kinds of portability that are absolutely necessary are quite +limited. But it is important to support Linux-based GNU systems, since +they are the form of GNU that is popular. + + Beyond that, it is good to support the other free operating systems +(*BSD), and it is nice to support other Unix-like systems if you want +to. Supporting a variety of Unix-like systems is desirable, although +not paramount. It is usually not too hard, so you may as well do it. +But you don't have to consider it an obligation, if it does turn out to +be hard. + + The easiest way to achieve portability to most Unix-like systems is +to use Autoconf. It's unlikely that your program needs to know more +information about the host platform than Autoconf can provide, simply +because most of the programs that need such knowledge have already been +written. + + Avoid using the format of semi-internal data bases (e.g., +directories) when there is a higher-level alternative (`readdir'). + + As for systems that are not like Unix, such as MSDOS, Windows, the +Macintosh, VMS, and MVS, supporting them is often a lot of work. When +that is the case, it is better to spend your time adding features that +will be useful on GNU and GNU/Linux, rather than on supporting other +incompatible systems. + + It is a good idea to define the "feature test macro" `_GNU_SOURCE' +when compiling your C files. When you compile on GNU or GNU/Linux, +this will enable the declarations of GNU library extension functions, +and that will usually give you a compiler error message if you define +the same function names in some other way in your program. (You don't +have to actually _use_ these functions, if you prefer to make the +program more portable to other systems.) + + But whether or not you use these GNU extensions, you should avoid +using their names for any other meanings. Doing so would make it hard +to move your code into other GNU programs. + + +File: standards.info, Node: CPU Portability, Next: System Functions, Prev: System Portability, Up: Writing C + +5.6 Portability between CPUs +============================ + +Even GNU systems will differ because of differences among CPU +types--for example, difference in byte ordering and alignment +requirements. It is absolutely essential to handle these differences. +However, don't make any effort to cater to the possibility that an +`int' will be less than 32 bits. We don't support 16-bit machines in +GNU. + + Similarly, don't make any effort to cater to the possibility that +`long' will be smaller than predefined types like `size_t'. For +example, the following code is ok: + + printf ("size = %lu\n", (unsigned long) sizeof array); + printf ("diff = %ld\n", (long) (pointer2 - pointer1)); + + 1989 Standard C requires this to work, and we know of only one +counterexample: 64-bit programs on Microsoft Windows IA-64. We will +leave it to those who want to port GNU programs to that environment to +figure out how to do it. + + Predefined file-size types like `off_t' are an exception: they are +longer than `long' on many platforms, so code like the above won't work +with them. One way to print an `off_t' value portably is to print its +digits yourself, one by one. + + Don't assume that the address of an `int' object is also the address +of its least-significant byte. This is false on big-endian machines. +Thus, don't make the following mistake: + + int c; + ... + while ((c = getchar()) != EOF) + write(file_descriptor, &c, 1); + + When calling functions, you need not worry about the difference +between pointers of various types, or between pointers and integers. +On most machines, there's no difference anyway. As for the few +machines where there is a difference, all of them support Standard C +prototypes, so you can use prototypes (perhaps conditionalized to be +active only in Standard C) to make the code work on those systems. + + In certain cases, it is ok to pass integer and pointer arguments +indiscriminately to the same function, and use no prototype on any +system. For example, many GNU programs have error-reporting functions +that pass their arguments along to `printf' and friends: + + error (s, a1, a2, a3) + char *s; + char *a1, *a2, *a3; + { + fprintf (stderr, "error: "); + fprintf (stderr, s, a1, a2, a3); + } + +In practice, this works on all machines, since a pointer is generally +the widest possible kind of argument; it is much simpler than any +"correct" alternative. Be sure _not_ to use a prototype for such +functions. + + If you have decided to use Standard C, then you can instead define +`error' using `stdarg.h', and pass the arguments along to `vfprintf'. + + Avoid casting pointers to integers if you can. Such casts greatly +reduce portability, and in most programs they are easy to avoid. In the +cases where casting pointers to integers is essential--such as, a Lisp +interpreter which stores type information as well as an address in one +word--you'll have to make explicit provisions to handle different word +sizes. You will also need to make provision for systems in which the +normal range of addresses you can get from `malloc' starts far away +from zero. + + +File: standards.info, Node: System Functions, Next: Internationalization, Prev: CPU Portability, Up: Writing C + +5.7 Calling System Functions +============================ + +C implementations differ substantially. Standard C reduces but does +not eliminate the incompatibilities; meanwhile, many GNU packages still +support pre-standard compilers because this is not hard to do. This +chapter gives recommendations for how to use the more-or-less standard C +library functions to avoid unnecessary loss of portability. + + * Don't use the return value of `sprintf'. It returns the number of + characters written on some systems, but not on all systems. + + * Be aware that `vfprintf' is not always available. + + * `main' should be declared to return type `int'. It should + terminate either by calling `exit' or by returning the integer + status code; make sure it cannot ever return an undefined value. + + * Don't declare system functions explicitly. + + Almost any declaration for a system function is wrong on some + system. To minimize conflicts, leave it to the system header + files to declare system functions. If the headers don't declare a + function, let it remain undeclared. + + While it may seem unclean to use a function without declaring it, + in practice this works fine for most system library functions on + the systems where this really happens; thus, the disadvantage is + only theoretical. By contrast, actual declarations have + frequently caused actual conflicts. + + * If you must declare a system function, don't specify the argument + types. Use an old-style declaration, not a Standard C prototype. + The more you specify about the function, the more likely a + conflict. + + * In particular, don't unconditionally declare `malloc' or `realloc'. + + Most GNU programs use those functions just once, in functions + conventionally named `xmalloc' and `xrealloc'. These functions + call `malloc' and `realloc', respectively, and check the results. + + Because `xmalloc' and `xrealloc' are defined in your program, you + can declare them in other files without any risk of type conflict. + + On most systems, `int' is the same length as a pointer; thus, the + calls to `malloc' and `realloc' work fine. For the few + exceptional systems (mostly 64-bit machines), you can use + *conditionalized* declarations of `malloc' and `realloc'--or put + these declarations in configuration files specific to those + systems. + + * The string functions require special treatment. Some Unix systems + have a header file `string.h'; others have `strings.h'. Neither + file name is portable. There are two things you can do: use + Autoconf to figure out which file to include, or don't include + either file. + + * If you don't include either strings file, you can't get + declarations for the string functions from the header file in the + usual way. + + That causes less of a problem than you might think. The newer + standard string functions should be avoided anyway because many + systems still don't support them. The string functions you can + use are these: + + strcpy strncpy strcat strncat + strlen strcmp strncmp + strchr strrchr + + The copy and concatenate functions work fine without a declaration + as long as you don't use their values. Using their values without + a declaration fails on systems where the width of a pointer + differs from the width of `int', and perhaps in other cases. It + is trivial to avoid using their values, so do that. + + The compare functions and `strlen' work fine without a declaration + on most systems, possibly all the ones that GNU software runs on. + You may find it necessary to declare them *conditionally* on a few + systems. + + The search functions must be declared to return `char *'. Luckily, + there is no variation in the data type they return. But there is + variation in their names. Some systems give these functions the + names `index' and `rindex'; other systems use the names `strchr' + and `strrchr'. Some systems support both pairs of names, but + neither pair works on all systems. + + You should pick a single pair of names and use it throughout your + program. (Nowadays, it is better to choose `strchr' and `strrchr' + for new programs, since those are the standard names.) Declare + both of those names as functions returning `char *'. On systems + which don't support those names, define them as macros in terms of + the other pair. For example, here is what to put at the beginning + of your file (or in a header) if you want to use the names + `strchr' and `strrchr' throughout: + + #ifndef HAVE_STRCHR + #define strchr index + #endif + #ifndef HAVE_STRRCHR + #define strrchr rindex + #endif + + char *strchr (); + char *strrchr (); + + Here we assume that `HAVE_STRCHR' and `HAVE_STRRCHR' are macros +defined in systems where the corresponding functions exist. One way to +get them properly defined is to use Autoconf. + + +File: standards.info, Node: Internationalization, Next: Mmap, Prev: System Functions, Up: Writing C + +5.8 Internationalization +======================== + +GNU has a library called GNU gettext that makes it easy to translate the +messages in a program into various languages. You should use this +library in every program. Use English for the messages as they appear +in the program, and let gettext provide the way to translate them into +other languages. + + Using GNU gettext involves putting a call to the `gettext' macro +around each string that might need translation--like this: + + printf (gettext ("Processing file `%s'...")); + +This permits GNU gettext to replace the string `"Processing file +`%s'..."' with a translated version. + + Once a program uses gettext, please make a point of writing calls to +`gettext' when you add new strings that call for translation. + + Using GNU gettext in a package involves specifying a "text domain +name" for the package. The text domain name is used to separate the +translations for this package from the translations for other packages. +Normally, the text domain name should be the same as the name of the +package--for example, `fileutils' for the GNU file utilities. + + To enable gettext to work well, avoid writing code that makes +assumptions about the structure of words or sentences. When you want +the precise text of a sentence to vary depending on the data, use two or +more alternative string constants each containing a complete sentences, +rather than inserting conditionalized words or phrases into a single +sentence framework. + + Here is an example of what not to do: + + printf ("%d file%s processed", nfiles, + nfiles != 1 ? "s" : ""); + +The problem with that example is that it assumes that plurals are made +by adding `s'. If you apply gettext to the format string, like this, + + printf (gettext ("%d file%s processed"), nfiles, + nfiles != 1 ? "s" : ""); + +the message can use different words, but it will still be forced to use +`s' for the plural. Here is a better way: + + printf ((nfiles != 1 ? "%d files processed" + : "%d file processed"), + nfiles); + +This way, you can apply gettext to each of the two strings +independently: + + printf ((nfiles != 1 ? gettext ("%d files processed") + : gettext ("%d file processed")), + nfiles); + +This can be any method of forming the plural of the word for "file", and +also handles languages that require agreement in the word for +"processed". + + A similar problem appears at the level of sentence structure with +this code: + + printf ("# Implicit rule search has%s been done.\n", + f->tried_implicit ? "" : " not"); + +Adding `gettext' calls to this code cannot give correct results for all +languages, because negation in some languages requires adding words at +more than one place in the sentence. By contrast, adding `gettext' +calls does the job straightfowardly if the code starts out like this: + + printf (f->tried_implicit + ? "# Implicit rule search has been done.\n", + : "# Implicit rule search has not been done.\n"); + + +File: standards.info, Node: Mmap, Prev: Internationalization, Up: Writing C + +5.9 Mmap +======== + +Don't assume that `mmap' either works on all files or fails for all +files. It may work on some files and fail on others. + + The proper way to use `mmap' is to try it on the specific file for +which you want to use it--and if `mmap' doesn't work, fall back on +doing the job in another way using `read' and `write'. + + The reason this precaution is needed is that the GNU kernel (the +HURD) provides a user-extensible file system, in which there can be many +different kinds of "ordinary files." Many of them support `mmap', but +some do not. It is important to make programs handle all these kinds +of files. + + +File: standards.info, Node: Documentation, Next: Managing Releases, Prev: Writing C, Up: Top + +6 Documenting Programs +********************** + +A GNU program should ideally come with full free documentation, adequate +for both reference and tutorial purposes. If the package can be +programmed or extended, the documentation should cover programming or +extending it, as well as just using it. + +* Menu: + +* GNU Manuals:: Writing proper manuals. +* Doc Strings and Manuals:: Compiling doc strings doesn't make a manual. +* Manual Structure Details:: Specific structure conventions. +* License for Manuals:: Writing the distribution terms for a manual. +* Manual Credits:: Giving credit to documentation contributors. +* Printed Manuals:: Mentioning the printed manual. +* NEWS File:: NEWS files supplement manuals. +* Change Logs:: Recording Changes +* Man Pages:: Man pages are secondary. +* Reading other Manuals:: How far you can go in learning + from other manuals. + + +File: standards.info, Node: GNU Manuals, Next: Doc Strings and Manuals, Up: Documentation + +6.1 GNU Manuals +=============== + +The preferred document format for the GNU system is the Texinfo +formatting language. Every GNU package should (ideally) have +documentation in Texinfo both for reference and for learners. Texinfo +makes it possible to produce a good quality formatted book, using TeX, +and to generate an Info file. It is also possible to generate HTML +output from Texinfo source. See the Texinfo manual, either the +hardcopy, or the on-line version available through `info' or the Emacs +Info subsystem (`C-h i'). + + Nowadays some other formats such as Docbook and Sgmltexi can be +converted automatically into Texinfo. It is ok to produce the Texinfo +documentation by conversion this way, as long as it gives good results. + + Programmers often find it most natural to structure the documentation +following the structure of the implementation, which they know. But +this structure is not necessarily good for explaining how to use the +program; it may be irrelevant and confusing for a user. + + At every level, from the sentences in a paragraph to the grouping of +topics into separate manuals, the right way to structure documentation +is according to the concepts and questions that a user will have in mind +when reading it. Sometimes this structure of ideas matches the +structure of the implementation of the software being documented--but +often they are different. Often the most important part of learning to +write good documentation is learning to notice when you are structuring +the documentation like the implementation, and think about better +alternatives. + + For example, each program in the GNU system probably ought to be +documented in one manual; but this does not mean each program should +have its own manual. That would be following the structure of the +implementation, rather than the structure that helps the user +understand. + + Instead, each manual should cover a coherent _topic_. For example, +instead of a manual for `diff' and a manual for `diff3', we have one +manual for "comparison of files" which covers both of those programs, +as well as `cmp'. By documenting these programs together, we can make +the whole subject clearer. + + The manual which discusses a program should certainly document all of +the program's command-line options and all of its commands. It should +give examples of their use. But don't organize the manual as a list of +features. Instead, organize it logically, by subtopics. Address the +questions that a user will ask when thinking about the job that the +program does. + + In general, a GNU manual should serve both as tutorial and reference. +It should be set up for convenient access to each topic through Info, +and for reading straight through (appendixes aside). A GNU manual +should give a good introduction to a beginner reading through from the +start, and should also provide all the details that hackers want. The +Bison manual is a good example of this--please take a look at it to see +what we mean. + + That is not as hard as it first sounds. Arrange each chapter as a +logical breakdown of its topic, but order the sections, and write their +text, so that reading the chapter straight through makes sense. Do +likewise when structuring the book into chapters, and when structuring a +section into paragraphs. The watchword is, _at each point, address the +most fundamental and important issue raised by the preceding text._ + + If necessary, add extra chapters at the beginning of the manual which +are purely tutorial and cover the basics of the subject. These provide +the framework for a beginner to understand the rest of the manual. The +Bison manual provides a good example of how to do this. + + To serve as a reference, a manual should have an Index that list all +the functions, variables, options, and important concepts that are part +of the program. One combined Index should do for a short manual, but +sometimes for a complex package it is better to use multiple indices. +The Texinfo manual includes advice on preparing good index entries, see +*note Making Index Entries: (texinfo)Index Entries, and see *note +Defining the Entries of an Index: (texinfo)Indexing Commands. + + Don't use Unix man pages as a model for how to write GNU +documentation; most of them are terse, badly structured, and give +inadequate explanation of the underlying concepts. (There are, of +course, some exceptions.) Also, Unix man pages use a particular format +which is different from what we use in GNU manuals. + + Please include an email address in the manual for where to report +bugs _in the manual_. + + Please do not use the term "pathname" that is used in Unix +documentation; use "file name" (two words) instead. We use the term +"path" only for search paths, which are lists of directory names. + + Please do not use the term "illegal" to refer to erroneous input to a +computer program. Please use "invalid" for this, and reserve the term +"illegal" for activities punishable by law. + + +File: standards.info, Node: Doc Strings and Manuals, Next: Manual Structure Details, Prev: GNU Manuals, Up: Documentation + +6.2 Doc Strings and Manuals +=========================== + +Some programming systems, such as Emacs, provide a documentation string +for each function, command or variable. You may be tempted to write a +reference manual by compiling the documentation strings and writing a +little additional text to go around them--but you must not do it. That +approach is a fundamental mistake. The text of well-written +documentation strings will be entirely wrong for a manual. + + A documentation string needs to stand alone--when it appears on the +screen, there will be no other text to introduce or explain it. +Meanwhile, it can be rather informal in style. + + The text describing a function or variable in a manual must not stand +alone; it appears in the context of a section or subsection. Other text +at the beginning of the section should explain some of the concepts, and +should often make some general points that apply to several functions or +variables. The previous descriptions of functions and variables in the +section will also have given information about the topic. A description +written to stand alone would repeat some of that information; this +redundance looks bad. Meanwhile, the informality that is acceptable in +a documentation string is totally unacceptable in a manual. + + The only good way to use documentation strings in writing a good +manual is to use them as a source of information for writing good text. + + +File: standards.info, Node: Manual Structure Details, Next: License for Manuals, Prev: Doc Strings and Manuals, Up: Documentation + +6.3 Manual Structure Details +============================ + +The title page of the manual should state the version of the programs or +packages documented in the manual. The Top node of the manual should +also contain this information. If the manual is changing more +frequently than or independent of the program, also state a version +number for the manual in both of these places. + + Each program documented in the manual should have a node named +`PROGRAM Invocation' or `Invoking PROGRAM'. This node (together with +its subnodes, if any) should describe the program's command line +arguments and how to run it (the sort of information people would look +in a man page for). Start with an `@example' containing a template for +all the options and arguments that the program uses. + + Alternatively, put a menu item in some menu whose item name fits one +of the above patterns. This identifies the node which that item points +to as the node for this purpose, regardless of the node's actual name. + + The `--usage' feature of the Info reader looks for such a node or +menu item in order to find the relevant text, so it is essential for +every Texinfo file to have one. + + If one manual describes several programs, it should have such a node +for each program described in the manual. + + +File: standards.info, Node: License for Manuals, Next: Manual Credits, Prev: Manual Structure Details, Up: Documentation + +6.4 License for Manuals +======================= + +Please use the GNU Free Documentation License for all GNU manuals that +are more than a few pages long. Likewise for a collection of short +documents--you only need one copy of the GNU FDL for the whole +collection. For a single short document, you can use a very permissive +non-copyleft license, to avoid taking up space with a long license. + + See `http://www.gnu.org/copyleft/fdl-howto.html' for more explanation +of how to employ the GFDL. + + Note that it is not obligatory to include a copy of the GNU GPL or +GNU LGPL in a manual whose license is neither the GPL nor the LGPL. It +can be a good idea to include the program's license in a large manual; +in a short manual, whose size would be increased considerably by +including the program's license, it is probably better not to include +it. + + +File: standards.info, Node: Manual Credits, Next: Printed Manuals, Prev: License for Manuals, Up: Documentation + +6.5 Manual Credits +================== + +Please credit the principal human writers of the manual as the authors, +on the title page of the manual. If a company sponsored the work, thank +the company in a suitable place in the manual, but do not cite the +company as an author. + + +File: standards.info, Node: Printed Manuals, Next: NEWS File, Prev: Manual Credits, Up: Documentation + +6.6 Printed Manuals +=================== + +The FSF publishes some GNU manuals in printed form. To encourage sales +of these manuals, the on-line versions of the manual should mention at +the very start that the printed manual is available and should point at +information for getting it--for instance, with a link to the page +`http://www.gnu.org/order/order.html'. This should not be included in +the printed manual, though, because there it is redundant. + + It is also useful to explain in the on-line forms of the manual how +the user can print out the manual from the sources. + + +File: standards.info, Node: NEWS File, Next: Change Logs, Prev: Printed Manuals, Up: Documentation + +6.7 The NEWS File +================= + +In addition to its manual, the package should have a file named `NEWS' +which contains a list of user-visible changes worth mentioning. In +each new release, add items to the front of the file and identify the +version they pertain to. Don't discard old items; leave them in the +file after the newer items. This way, a user upgrading from any +previous version can see what is new. + + If the `NEWS' file gets very long, move some of the older items into +a file named `ONEWS' and put a note at the end referring the user to +that file. + + +File: standards.info, Node: Change Logs, Next: Man Pages, Prev: NEWS File, Up: Documentation + +6.8 Change Logs +=============== + +Keep a change log to describe all the changes made to program source +files. The purpose of this is so that people investigating bugs in the +future will know about the changes that might have introduced the bug. +Often a new bug can be found by looking at what was recently changed. +More importantly, change logs can help you eliminate conceptual +inconsistencies between different parts of a program, by giving you a +history of how the conflicting concepts arose and who they came from. + +* Menu: + +* Change Log Concepts:: +* Style of Change Logs:: +* Simple Changes:: +* Conditional Changes:: +* Indicating the Part Changed:: + + +File: standards.info, Node: Change Log Concepts, Next: Style of Change Logs, Up: Change Logs + +6.8.1 Change Log Concepts +------------------------- + +You can think of the change log as a conceptual "undo list" which +explains how earlier versions were different from the current version. +People can see the current version; they don't need the change log to +tell them what is in it. What they want from a change log is a clear +explanation of how the earlier version differed. + + The change log file is normally called `ChangeLog' and covers an +entire directory. Each directory can have its own change log, or a +directory can use the change log of its parent directory-it's up to you. + + Another alternative is to record change log information with a +version control system such as RCS or CVS. This can be converted +automatically to a `ChangeLog' file using `rcs2log'; in Emacs, the +command `C-x v a' (`vc-update-change-log') does the job. + + There's no need to describe the full purpose of the changes or how +they work together. If you think that a change calls for explanation, +you're probably right. Please do explain it--but please put the +explanation in comments in the code, where people will see it whenever +they see the code. For example, "New function" is enough for the +change log when you add a function, because there should be a comment +before the function definition to explain what it does. + + However, sometimes it is useful to write one line to describe the +overall purpose of a batch of changes. + + The easiest way to add an entry to `ChangeLog' is with the Emacs +command `M-x add-change-log-entry'. An entry should have an asterisk, +the name of the changed file, and then in parentheses the name of the +changed functions, variables or whatever, followed by a colon. Then +describe the changes you made to that function or variable. + + +File: standards.info, Node: Style of Change Logs, Next: Simple Changes, Prev: Change Log Concepts, Up: Change Logs + +6.8.2 Style of Change Logs +-------------------------- + +Here are some simple examples of change log entries, starting with the +header line that says who made the change and when, followed by +descriptions of specific changes. (These examples are drawn from Emacs +and GCC.) + + 1998-08-17 Richard Stallman <rms@gnu.org> + + * register.el (insert-register): Return nil. + (jump-to-register): Likewise. + + * sort.el (sort-subr): Return nil. + + * tex-mode.el (tex-bibtex-file, tex-file, tex-region): + Restart the tex shell if process is gone or stopped. + (tex-shell-running): New function. + + * expr.c (store_one_arg): Round size up for move_block_to_reg. + (expand_call): Round up when emitting USE insns. + * stmt.c (assign_parms): Round size up for move_block_from_reg. + + It's important to name the changed function or variable in full. +Don't abbreviate function or variable names, and don't combine them. +Subsequent maintainers will often search for a function name to find all +the change log entries that pertain to it; if you abbreviate the name, +they won't find it when they search. + + For example, some people are tempted to abbreviate groups of function +names by writing `* register.el ({insert,jump-to}-register)'; this is +not a good idea, since searching for `jump-to-register' or +`insert-register' would not find that entry. + + Separate unrelated change log entries with blank lines. When two +entries represent parts of the same change, so that they work together, +then don't put blank lines between them. Then you can omit the file +name and the asterisk when successive entries are in the same file. + + Break long lists of function names by closing continued lines with +`)', rather than `,', and opening the continuation with `(' as in this +example: + + * keyboard.c (menu_bar_items, tool_bar_items) + (Fexecute_extended_command): Deal with `keymap' property. + + +File: standards.info, Node: Simple Changes, Next: Conditional Changes, Prev: Style of Change Logs, Up: Change Logs + +6.8.3 Simple Changes +-------------------- + +Certain simple kinds of changes don't need much detail in the change +log. + + When you change the calling sequence of a function in a simple +fashion, and you change all the callers of the function to use the new +calling sequence, there is no need to make individual entries for all +the callers that you changed. Just write in the entry for the function +being called, "All callers changed"--like this: + + * keyboard.c (Fcommand_execute): New arg SPECIAL. + All callers changed. + + When you change just comments or doc strings, it is enough to write +an entry for the file, without mentioning the functions. Just "Doc +fixes" is enough for the change log. + + There's no need to make change log entries for documentation files. +This is because documentation is not susceptible to bugs that are hard +to fix. Documentation does not consist of parts that must interact in a +precisely engineered fashion. To correct an error, you need not know +the history of the erroneous passage; it is enough to compare what the +documentation says with the way the program actually works. + + +File: standards.info, Node: Conditional Changes, Next: Indicating the Part Changed, Prev: Simple Changes, Up: Change Logs + +6.8.4 Conditional Changes +------------------------- + +C programs often contain compile-time `#if' conditionals. Many changes +are conditional; sometimes you add a new definition which is entirely +contained in a conditional. It is very useful to indicate in the +change log the conditions for which the change applies. + + Our convention for indicating conditional changes is to use square +brackets around the name of the condition. + + Here is a simple example, describing a change which is conditional +but does not have a function or entity name associated with it: + + * xterm.c [SOLARIS2]: Include string.h. + + Here is an entry describing a new definition which is entirely +conditional. This new definition for the macro `FRAME_WINDOW_P' is +used only when `HAVE_X_WINDOWS' is defined: + + * frame.h [HAVE_X_WINDOWS] (FRAME_WINDOW_P): Macro defined. + + Here is an entry for a change within the function `init_display', +whose definition as a whole is unconditional, but the changes themselves +are contained in a `#ifdef HAVE_LIBNCURSES' conditional: + + * dispnew.c (init_display) [HAVE_LIBNCURSES]: If X, call tgetent. + + Here is an entry for a change that takes affect only when a certain +macro is _not_ defined: + + (gethostname) [!HAVE_SOCKETS]: Replace with winsock version. + + +File: standards.info, Node: Indicating the Part Changed, Prev: Conditional Changes, Up: Change Logs + +6.8.5 Indicating the Part Changed +--------------------------------- + +Indicate the part of a function which changed by using angle brackets +enclosing an indication of what the changed part does. Here is an entry +for a change in the part of the function `sh-while-getopts' that deals +with `sh' commands: + + * progmodes/sh-script.el (sh-while-getopts) <sh>: Handle case that + user-specified option string is empty. + + +File: standards.info, Node: Man Pages, Next: Reading other Manuals, Prev: Change Logs, Up: Documentation + +6.9 Man Pages +============= + +In the GNU project, man pages are secondary. It is not necessary or +expected for every GNU program to have a man page, but some of them do. +It's your choice whether to include a man page in your program. + + When you make this decision, consider that supporting a man page +requires continual effort each time the program is changed. The time +you spend on the man page is time taken away from more useful work. + + For a simple program which changes little, updating the man page may +be a small job. Then there is little reason not to include a man page, +if you have one. + + For a large program that changes a great deal, updating a man page +may be a substantial burden. If a user offers to donate a man page, +you may find this gift costly to accept. It may be better to refuse +the man page unless the same person agrees to take full responsibility +for maintaining it--so that you can wash your hands of it entirely. If +this volunteer later ceases to do the job, then don't feel obliged to +pick it up yourself; it may be better to withdraw the man page from the +distribution until someone else agrees to update it. + + When a program changes only a little, you may feel that the +discrepancies are small enough that the man page remains useful without +updating. If so, put a prominent note near the beginning of the man +page explaining that you don't maintain it and that the Texinfo manual +is more authoritative. The note should say how to access the Texinfo +documentation. + + +File: standards.info, Node: Reading other Manuals, Prev: Man Pages, Up: Documentation + +6.10 Reading other Manuals +========================== + +There may be non-free books or documentation files that describe the +program you are documenting. + + It is ok to use these documents for reference, just as the author of +a new algebra textbook can read other books on algebra. A large portion +of any non-fiction book consists of facts, in this case facts about how +a certain program works, and these facts are necessarily the same for +everyone who writes about the subject. But be careful not to copy your +outline structure, wording, tables or examples from preexisting non-free +documentation. Copying from free documentation may be ok; please check +with the FSF about the individual case. + + +File: standards.info, Node: Managing Releases, Next: References, Prev: Documentation, Up: Top + +7 The Release Process +********************* + +Making a release is more than just bundling up your source files in a +tar file and putting it up for FTP. You should set up your software so +that it can be configured to run on a variety of systems. Your Makefile +should conform to the GNU standards described below, and your directory +layout should also conform to the standards discussed below. Doing so +makes it easy to include your package into the larger framework of all +GNU software. + +* Menu: + +* Configuration:: How Configuration Should Work +* Makefile Conventions:: Makefile Conventions +* Releases:: Making Releases + + +File: standards.info, Node: Configuration, Next: Makefile Conventions, Up: Managing Releases + +7.1 How Configuration Should Work +================================= + +Each GNU distribution should come with a shell script named +`configure'. This script is given arguments which describe the kind of +machine and system you want to compile the program for. + + The `configure' script must record the configuration options so that +they affect compilation. + + One way to do this is to make a link from a standard name such as +`config.h' to the proper configuration file for the chosen system. If +you use this technique, the distribution should _not_ contain a file +named `config.h'. This is so that people won't be able to build the +program without configuring it first. + + Another thing that `configure' can do is to edit the Makefile. If +you do this, the distribution should _not_ contain a file named +`Makefile'. Instead, it should include a file `Makefile.in' which +contains the input used for editing. Once again, this is so that people +won't be able to build the program without configuring it first. + + If `configure' does write the `Makefile', then `Makefile' should +have a target named `Makefile' which causes `configure' to be rerun, +setting up the same configuration that was set up last time. The files +that `configure' reads should be listed as dependencies of `Makefile'. + + All the files which are output from the `configure' script should +have comments at the beginning explaining that they were generated +automatically using `configure'. This is so that users won't think of +trying to edit them by hand. + + The `configure' script should write a file named `config.status' +which describes which configuration options were specified when the +program was last configured. This file should be a shell script which, +if run, will recreate the same configuration. + + The `configure' script should accept an option of the form +`--srcdir=DIRNAME' to specify the directory where sources are found (if +it is not the current directory). This makes it possible to build the +program in a separate directory, so that the actual source directory is +not modified. + + If the user does not specify `--srcdir', then `configure' should +check both `.' and `..' to see if it can find the sources. If it finds +the sources in one of these places, it should use them from there. +Otherwise, it should report that it cannot find the sources, and should +exit with nonzero status. + + Usually the easy way to support `--srcdir' is by editing a +definition of `VPATH' into the Makefile. Some rules may need to refer +explicitly to the specified source directory. To make this possible, +`configure' can add to the Makefile a variable named `srcdir' whose +value is precisely the specified directory. + + The `configure' script should also take an argument which specifies +the type of system to build the program for. This argument should look +like this: + + CPU-COMPANY-SYSTEM + + For example, a Sun 3 might be `m68k-sun-sunos4.1'. + + The `configure' script needs to be able to decode all plausible +alternatives for how to describe a machine. Thus, `sun3-sunos4.1' +would be a valid alias. For many programs, `vax-dec-ultrix' would be +an alias for `vax-dec-bsd', simply because the differences between +Ultrix and BSD are rarely noticeable, but a few programs might need to +distinguish them. + + There is a shell script called `config.sub' that you can use as a +subroutine to validate system types and canonicalize aliases. + + Other options are permitted to specify in more detail the software +or hardware present on the machine, and include or exclude optional +parts of the package: + +`--enable-FEATURE[=PARAMETER]' + Configure the package to build and install an optional user-level + facility called FEATURE. This allows users to choose which + optional features to include. Giving an optional PARAMETER of + `no' should omit FEATURE, if it is built by default. + + No `--enable' option should *ever* cause one feature to replace + another. No `--enable' option should ever substitute one useful + behavior for another useful behavior. The only proper use for + `--enable' is for questions of whether to build part of the program + or exclude it. + +`--with-PACKAGE' + The package PACKAGE will be installed, so configure this package + to work with PACKAGE. + + Possible values of PACKAGE include `gnu-as' (or `gas'), `gnu-ld', + `gnu-libc', `gdb', `x', and `x-toolkit'. + + Do not use a `--with' option to specify the file name to use to + find certain files. That is outside the scope of what `--with' + options are for. + + All `configure' scripts should accept all of these "detail" options, +whether or not they make any difference to the particular package at +hand. In particular, they should accept any option that starts with +`--with-' or `--enable-'. This is so users will be able to configure +an entire GNU source tree at once with a single set of options. + + You will note that the categories `--with-' and `--enable-' are +narrow: they *do not* provide a place for any sort of option you might +think of. That is deliberate. We want to limit the possible +configuration options in GNU software. We do not want GNU programs to +have idiosyncratic configuration options. + + Packages that perform part of the compilation process may support +cross-compilation. In such a case, the host and target machines for the +program may be different. + + The `configure' script should normally treat the specified type of +system as both the host and the target, thus producing a program which +works for the same type of machine that it runs on. + + To configure a cross-compiler, cross-assembler, or what have you, you +should specify a target different from the host, using the configure +option `--target=TARGETTYPE'. The syntax for TARGETTYPE is the same as +for the host type. So the command would look like this: + + ./configure HOSTTYPE --target=TARGETTYPE + + Programs for which cross-operation is not meaningful need not accept +the `--target' option, because configuring an entire operating system +for cross-operation is not a meaningful operation. + + Bootstrapping a cross-compiler requires compiling it on a machine +other than the host it will run on. Compilation packages accept a +configuration option `--build=BUILDTYPE' for specifying the +configuration on which you will compile them, but the configure script +should normally guess the build machine type (using `config.guess'), so +this option is probably not necessary. The host and target types +normally default from the build type, so in bootstrapping a +cross-compiler you must specify them both explicitly. + + Some programs have ways of configuring themselves automatically. If +your program is set up to do this, your `configure' script can simply +ignore most of its arguments. + + +File: standards.info, Node: Makefile Conventions, Next: Releases, Prev: Configuration, Up: Managing Releases + +7.2 Makefile Conventions +======================== + +This node describes conventions for writing the Makefiles for GNU +programs. Using Automake will help you write a Makefile that follows +these conventions. + +* Menu: + +* Makefile Basics:: General Conventions for Makefiles +* Utilities in Makefiles:: Utilities in Makefiles +* Command Variables:: Variables for Specifying Commands +* Directory Variables:: Variables for Installation Directories +* Standard Targets:: Standard Targets for Users +* Install Command Categories:: Three categories of commands in the `install' + rule: normal, pre-install and post-install. + + +File: standards.info, Node: Makefile Basics, Next: Utilities in Makefiles, Up: Makefile Conventions + +7.2.1 General Conventions for Makefiles +--------------------------------------- + +Every Makefile should contain this line: + + SHELL = /bin/sh + +to avoid trouble on systems where the `SHELL' variable might be +inherited from the environment. (This is never a problem with GNU +`make'.) + + Different `make' programs have incompatible suffix lists and +implicit rules, and this sometimes creates confusion or misbehavior. So +it is a good idea to set the suffix list explicitly using only the +suffixes you need in the particular Makefile, like this: + + .SUFFIXES: + .SUFFIXES: .c .o + +The first line clears out the suffix list, the second introduces all +suffixes which may be subject to implicit rules in this Makefile. + + Don't assume that `.' is in the path for command execution. When +you need to run programs that are a part of your package during the +make, please make sure that it uses `./' if the program is built as +part of the make or `$(srcdir)/' if the file is an unchanging part of +the source code. Without one of these prefixes, the current search +path is used. + + The distinction between `./' (the "build directory") and +`$(srcdir)/' (the "source directory") is important because users can +build in a separate directory using the `--srcdir' option to +`configure'. A rule of the form: + + foo.1 : foo.man sedscript + sed -e sedscript foo.man > foo.1 + +will fail when the build directory is not the source directory, because +`foo.man' and `sedscript' are in the source directory. + + When using GNU `make', relying on `VPATH' to find the source file +will work in the case where there is a single dependency file, since +the `make' automatic variable `$<' will represent the source file +wherever it is. (Many versions of `make' set `$<' only in implicit +rules.) A Makefile target like + + foo.o : bar.c + $(CC) -I. -I$(srcdir) $(CFLAGS) -c bar.c -o foo.o + +should instead be written as + + foo.o : bar.c + $(CC) -I. -I$(srcdir) $(CFLAGS) -c $< -o $@ + +in order to allow `VPATH' to work correctly. When the target has +multiple dependencies, using an explicit `$(srcdir)' is the easiest way +to make the rule work well. For example, the target above for `foo.1' +is best written as: + + foo.1 : foo.man sedscript + sed -e $(srcdir)/sedscript $(srcdir)/foo.man > $@ + + GNU distributions usually contain some files which are not source +files--for example, Info files, and the output from Autoconf, Automake, +Bison or Flex. Since these files normally appear in the source +directory, they should always appear in the source directory, not in the +build directory. So Makefile rules to update them should put the +updated files in the source directory. + + However, if a file does not appear in the distribution, then the +Makefile should not put it in the source directory, because building a +program in ordinary circumstances should not modify the source directory +in any way. + + Try to make the build and installation targets, at least (and all +their subtargets) work correctly with a parallel `make'. + + +File: standards.info, Node: Utilities in Makefiles, Next: Command Variables, Prev: Makefile Basics, Up: Makefile Conventions + +7.2.2 Utilities in Makefiles +---------------------------- + +Write the Makefile commands (and any shell scripts, such as +`configure') to run in `sh', not in `csh'. Don't use any special +features of `ksh' or `bash'. + + The `configure' script and the Makefile rules for building and +installation should not use any utilities directly except these: + + cat cmp cp diff echo egrep expr false grep install-info + ln ls mkdir mv pwd rm rmdir sed sleep sort tar test touch true + + The compression program `gzip' can be used in the `dist' rule. + + Stick to the generally supported options for these programs. For +example, don't use `mkdir -p', convenient as it may be, because most +systems don't support it. + + It is a good idea to avoid creating symbolic links in makefiles, +since a few systems don't support them. + + The Makefile rules for building and installation can also use +compilers and related programs, but should do so via `make' variables +so that the user can substitute alternatives. Here are some of the +programs we mean: + + ar bison cc flex install ld ldconfig lex + make makeinfo ranlib texi2dvi yacc + + Use the following `make' variables to run those programs: + + $(AR) $(BISON) $(CC) $(FLEX) $(INSTALL) $(LD) $(LDCONFIG) $(LEX) + $(MAKE) $(MAKEINFO) $(RANLIB) $(TEXI2DVI) $(YACC) + + When you use `ranlib' or `ldconfig', you should make sure nothing +bad happens if the system does not have the program in question. +Arrange to ignore an error from that command, and print a message before +the command to tell the user that failure of this command does not mean +a problem. (The Autoconf `AC_PROG_RANLIB' macro can help with this.) + + If you use symbolic links, you should implement a fallback for +systems that don't have symbolic links. + + Additional utilities that can be used via Make variables are: + + chgrp chmod chown mknod + + It is ok to use other utilities in Makefile portions (or scripts) +intended only for particular systems where you know those utilities +exist. + + +File: standards.info, Node: Command Variables, Next: Directory Variables, Prev: Utilities in Makefiles, Up: Makefile Conventions + +7.2.3 Variables for Specifying Commands +--------------------------------------- + +Makefiles should provide variables for overriding certain commands, +options, and so on. + + In particular, you should run most utility programs via variables. +Thus, if you use Bison, have a variable named `BISON' whose default +value is set with `BISON = bison', and refer to it with `$(BISON)' +whenever you need to use Bison. + + File management utilities such as `ln', `rm', `mv', and so on, need +not be referred to through variables in this way, since users don't +need to replace them with other programs. + + Each program-name variable should come with an options variable that +is used to supply options to the program. Append `FLAGS' to the +program-name variable name to get the options variable name--for +example, `BISONFLAGS'. (The names `CFLAGS' for the C compiler, +`YFLAGS' for yacc, and `LFLAGS' for lex, are exceptions to this rule, +but we keep them because they are standard.) Use `CPPFLAGS' in any +compilation command that runs the preprocessor, and use `LDFLAGS' in +any compilation command that does linking as well as in any direct use +of `ld'. + + If there are C compiler options that _must_ be used for proper +compilation of certain files, do not include them in `CFLAGS'. Users +expect to be able to specify `CFLAGS' freely themselves. Instead, +arrange to pass the necessary options to the C compiler independently +of `CFLAGS', by writing them explicitly in the compilation commands or +by defining an implicit rule, like this: + + CFLAGS = -g + ALL_CFLAGS = -I. $(CFLAGS) + .c.o: + $(CC) -c $(CPPFLAGS) $(ALL_CFLAGS) $< + + Do include the `-g' option in `CFLAGS', because that is not +_required_ for proper compilation. You can consider it a default that +is only recommended. If the package is set up so that it is compiled +with GCC by default, then you might as well include `-O' in the default +value of `CFLAGS' as well. + + Put `CFLAGS' last in the compilation command, after other variables +containing compiler options, so the user can use `CFLAGS' to override +the others. + + `CFLAGS' should be used in every invocation of the C compiler, both +those which do compilation and those which do linking. + + Every Makefile should define the variable `INSTALL', which is the +basic command for installing a file into the system. + + Every Makefile should also define the variables `INSTALL_PROGRAM' +and `INSTALL_DATA'. (The default for `INSTALL_PROGRAM' should be +`$(INSTALL)'; the default for `INSTALL_DATA' should be `${INSTALL} -m +644'.) Then it should use those variables as the commands for actual +installation, for executables and nonexecutables respectively. Use +these variables as follows: + + $(INSTALL_PROGRAM) foo $(bindir)/foo + $(INSTALL_DATA) libfoo.a $(libdir)/libfoo.a + + Optionally, you may prepend the value of `DESTDIR' to the target +filename. Doing this allows the installer to create a snapshot of the +installation to be copied onto the real target filesystem later. Do not +set the value of `DESTDIR' in your Makefile, and do not include it in +any installed files. With support for `DESTDIR', the above examples +become: + + $(INSTALL_PROGRAM) foo $(DESTDIR)$(bindir)/foo + $(INSTALL_DATA) libfoo.a $(DESTDIR)$(libdir)/libfoo.a + +Always use a file name, not a directory name, as the second argument of +the installation commands. Use a separate command for each file to be +installed. + + +File: standards.info, Node: Directory Variables, Next: Standard Targets, Prev: Command Variables, Up: Makefile Conventions + +7.2.4 Variables for Installation Directories +-------------------------------------------- + +Installation directories should always be named by variables, so it is +easy to install in a nonstandard place. The standard names for these +variables are described below. They are based on a standard filesystem +layout; variants of it are used in SVR4, 4.4BSD, GNU/Linux, Ultrix v4, +and other modern operating systems. + + These two variables set the root for the installation. All the other +installation directories should be subdirectories of one of these two, +and nothing should be directly installed into these two directories. + +`prefix' + A prefix used in constructing the default values of the variables + listed below. The default value of `prefix' should be + `/usr/local'. When building the complete GNU system, the prefix + will be empty and `/usr' will be a symbolic link to `/'. (If you + are using Autoconf, write it as `@prefix@'.) + + Running `make install' with a different value of `prefix' from the + one used to build the program should _not_ recompile the program. + +`exec_prefix' + A prefix used in constructing the default values of some of the + variables listed below. The default value of `exec_prefix' should + be `$(prefix)'. (If you are using Autoconf, write it as + `@exec_prefix@'.) + + Generally, `$(exec_prefix)' is used for directories that contain + machine-specific files (such as executables and subroutine + libraries), while `$(prefix)' is used directly for other + directories. + + Running `make install' with a different value of `exec_prefix' + from the one used to build the program should _not_ recompile the + program. + + Executable programs are installed in one of the following +directories. + +`bindir' + The directory for installing executable programs that users can + run. This should normally be `/usr/local/bin', but write it as + `$(exec_prefix)/bin'. (If you are using Autoconf, write it as + `@bindir@'.) + +`sbindir' + The directory for installing executable programs that can be run + from the shell, but are only generally useful to system + administrators. This should normally be `/usr/local/sbin', but + write it as `$(exec_prefix)/sbin'. (If you are using Autoconf, + write it as `@sbindir@'.) + +`libexecdir' + The directory for installing executable programs to be run by other + programs rather than by users. This directory should normally be + `/usr/local/libexec', but write it as `$(exec_prefix)/libexec'. + (If you are using Autoconf, write it as `@libexecdir@'.) + + Data files used by the program during its execution are divided into +categories in two ways. + + * Some files are normally modified by programs; others are never + normally modified (though users may edit some of these). + + * Some files are architecture-independent and can be shared by all + machines at a site; some are architecture-dependent and can be + shared only by machines of the same kind and operating system; + others may never be shared between two machines. + + This makes for six different possibilities. However, we want to +discourage the use of architecture-dependent files, aside from object +files and libraries. It is much cleaner to make other data files +architecture-independent, and it is generally not hard. + + Therefore, here are the variables Makefiles should use to specify +directories: + +`datadir' + The directory for installing read-only architecture independent + data files. This should normally be `/usr/local/share', but write + it as `$(prefix)/share'. (If you are using Autoconf, write it as + `@datadir@'.) As a special exception, see `$(infodir)' and + `$(includedir)' below. + +`sysconfdir' + The directory for installing read-only data files that pertain to a + single machine-that is to say, files for configuring a host. + Mailer and network configuration files, `/etc/passwd', and so + forth belong here. All the files in this directory should be + ordinary ASCII text files. This directory should normally be + `/usr/local/etc', but write it as `$(prefix)/etc'. (If you are + using Autoconf, write it as `@sysconfdir@'.) + + Do not install executables here in this directory (they probably + belong in `$(libexecdir)' or `$(sbindir)'). Also do not install + files that are modified in the normal course of their use (programs + whose purpose is to change the configuration of the system + excluded). Those probably belong in `$(localstatedir)'. + +`sharedstatedir' + The directory for installing architecture-independent data files + which the programs modify while they run. This should normally be + `/usr/local/com', but write it as `$(prefix)/com'. (If you are + using Autoconf, write it as `@sharedstatedir@'.) + +`localstatedir' + The directory for installing data files which the programs modify + while they run, and that pertain to one specific machine. Users + should never need to modify files in this directory to configure + the package's operation; put such configuration information in + separate files that go in `$(datadir)' or `$(sysconfdir)'. + `$(localstatedir)' should normally be `/usr/local/var', but write + it as `$(prefix)/var'. (If you are using Autoconf, write it as + `@localstatedir@'.) + +`libdir' + The directory for object files and libraries of object code. Do + not install executables here, they probably ought to go in + `$(libexecdir)' instead. The value of `libdir' should normally be + `/usr/local/lib', but write it as `$(exec_prefix)/lib'. (If you + are using Autoconf, write it as `@libdir@'.) + +`infodir' + The directory for installing the Info files for this package. By + default, it should be `/usr/local/info', but it should be written + as `$(prefix)/info'. (If you are using Autoconf, write it as + `@infodir@'.) + +`lispdir' + The directory for installing any Emacs Lisp files in this package. + By default, it should be `/usr/local/share/emacs/site-lisp', but it + should be written as `$(prefix)/share/emacs/site-lisp'. + + If you are using Autoconf, write the default as `@lispdir@'. In + order to make `@lispdir@' work, you need the following lines in + your `configure.in' file: + + lispdir='${datadir}/emacs/site-lisp' + AC_SUBST(lispdir) + +`includedir' + The directory for installing header files to be included by user + programs with the C `#include' preprocessor directive. This + should normally be `/usr/local/include', but write it as + `$(prefix)/include'. (If you are using Autoconf, write it as + `@includedir@'.) + + Most compilers other than GCC do not look for header files in + directory `/usr/local/include'. So installing the header files + this way is only useful with GCC. Sometimes this is not a problem + because some libraries are only really intended to work with GCC. + But some libraries are intended to work with other compilers. + They should install their header files in two places, one + specified by `includedir' and one specified by `oldincludedir'. + +`oldincludedir' + The directory for installing `#include' header files for use with + compilers other than GCC. This should normally be `/usr/include'. + (If you are using Autoconf, you can write it as `@oldincludedir@'.) + + The Makefile commands should check whether the value of + `oldincludedir' is empty. If it is, they should not try to use + it; they should cancel the second installation of the header files. + + A package should not replace an existing header in this directory + unless the header came from the same package. Thus, if your Foo + package provides a header file `foo.h', then it should install the + header file in the `oldincludedir' directory if either (1) there + is no `foo.h' there or (2) the `foo.h' that exists came from the + Foo package. + + To tell whether `foo.h' came from the Foo package, put a magic + string in the file--part of a comment--and `grep' for that string. + + Unix-style man pages are installed in one of the following: + +`mandir' + The top-level directory for installing the man pages (if any) for + this package. It will normally be `/usr/local/man', but you should + write it as `$(prefix)/man'. (If you are using Autoconf, write it + as `@mandir@'.) + +`man1dir' + The directory for installing section 1 man pages. Write it as + `$(mandir)/man1'. + +`man2dir' + The directory for installing section 2 man pages. Write it as + `$(mandir)/man2' + +`...' + *Don't make the primary documentation for any GNU software be a + man page. Write a manual in Texinfo instead. Man pages are just + for the sake of people running GNU software on Unix, which is a + secondary application only.* + +`manext' + The file name extension for the installed man page. This should + contain a period followed by the appropriate digit; it should + normally be `.1'. + +`man1ext' + The file name extension for installed section 1 man pages. + +`man2ext' + The file name extension for installed section 2 man pages. + +`...' + Use these names instead of `manext' if the package needs to + install man pages in more than one section of the manual. + + And finally, you should set the following variable: + +`srcdir' + The directory for the sources being compiled. The value of this + variable is normally inserted by the `configure' shell script. + (If you are using Autconf, use `srcdir = @srcdir@'.) + + For example: + + # Common prefix for installation directories. + # NOTE: This directory must exist when you start the install. + prefix = /usr/local + exec_prefix = $(prefix) + # Where to put the executable for the command `gcc'. + bindir = $(exec_prefix)/bin + # Where to put the directories used by the compiler. + libexecdir = $(exec_prefix)/libexec + # Where to put the Info files. + infodir = $(prefix)/info + + If your program installs a large number of files into one of the +standard user-specified directories, it might be useful to group them +into a subdirectory particular to that program. If you do this, you +should write the `install' rule to create these subdirectories. + + Do not expect the user to include the subdirectory name in the value +of any of the variables listed above. The idea of having a uniform set +of variable names for installation directories is to enable the user to +specify the exact same values for several different GNU packages. In +order for this to be useful, all the packages must be designed so that +they will work sensibly when the user does so. + + +File: standards.info, Node: Standard Targets, Next: Install Command Categories, Prev: Directory Variables, Up: Makefile Conventions + +7.2.5 Standard Targets for Users +-------------------------------- + +All GNU programs should have the following targets in their Makefiles: + +`all' + Compile the entire program. This should be the default target. + This target need not rebuild any documentation files; Info files + should normally be included in the distribution, and DVI files + should be made only when explicitly asked for. + + By default, the Make rules should compile and link with `-g', so + that executable programs have debugging symbols. Users who don't + mind being helpless can strip the executables later if they wish. + +`install' + Compile the program and copy the executables, libraries, and so on + to the file names where they should reside for actual use. If + there is a simple test to verify that a program is properly + installed, this target should run that test. + + Do not strip executables when installing them. Devil-may-care + users can use the `install-strip' target to do that. + + If possible, write the `install' target rule so that it does not + modify anything in the directory where the program was built, + provided `make all' has just been done. This is convenient for + building the program under one user name and installing it under + another. + + The commands should create all the directories in which files are + to be installed, if they don't already exist. This includes the + directories specified as the values of the variables `prefix' and + `exec_prefix', as well as all subdirectories that are needed. One + way to do this is by means of an `installdirs' target as described + below. + + Use `-' before any command for installing a man page, so that + `make' will ignore any errors. This is in case there are systems + that don't have the Unix man page documentation system installed. + + The way to install Info files is to copy them into `$(infodir)' + with `$(INSTALL_DATA)' (*note Command Variables::), and then run + the `install-info' program if it is present. `install-info' is a + program that edits the Info `dir' file to add or update the menu + entry for the given Info file; it is part of the Texinfo package. + Here is a sample rule to install an Info file: + + $(DESTDIR)$(infodir)/foo.info: foo.info + $(POST_INSTALL) + # There may be a newer info file in . than in srcdir. + -if test -f foo.info; then d=.; \ + else d=$(srcdir); fi; \ + $(INSTALL_DATA) $$d/foo.info $(DESTDIR)$@; \ + # Run install-info only if it exists. + # Use `if' instead of just prepending `-' to the + # line so we notice real errors from install-info. + # We use `$(SHELL) -c' because some shells do not + # fail gracefully when there is an unknown command. + if $(SHELL) -c 'install-info --version' \ + >/dev/null 2>&1; then \ + install-info --dir-file=$(DESTDIR)$(infodir)/dir \ + $(DESTDIR)$(infodir)/foo.info; \ + else true; fi + + When writing the `install' target, you must classify all the + commands into three categories: normal ones, "pre-installation" + commands and "post-installation" commands. *Note Install Command + Categories::. + +`uninstall' + Delete all the installed files--the copies that the `install' + target creates. + + This rule should not modify the directories where compilation is + done, only the directories where files are installed. + + The uninstallation commands are divided into three categories, + just like the installation commands. *Note Install Command + Categories::. + +`install-strip' + Like `install', but strip the executable files while installing + them. In simple cases, this target can use the `install' target in + a simple way: + + install-strip: + $(MAKE) INSTALL_PROGRAM='$(INSTALL_PROGRAM) -s' \ + install + + But if the package installs scripts as well as real executables, + the `install-strip' target can't just refer to the `install' + target; it has to strip the executables but not the scripts. + + `install-strip' should not strip the executables in the build + directory which are being copied for installation. It should only + strip the copies that are installed. + + Normally we do not recommend stripping an executable unless you + are sure the program has no bugs. However, it can be reasonable + to install a stripped executable for actual execution while saving + the unstripped executable elsewhere in case there is a bug. + +`clean' + Delete all files from the current directory that are normally + created by building the program. Don't delete the files that + record the configuration. Also preserve files that could be made + by building, but normally aren't because the distribution comes + with them. + + Delete `.dvi' files here if they are not part of the distribution. + +`distclean' + Delete all files from the current directory that are created by + configuring or building the program. If you have unpacked the + source and built the program without creating any other files, + `make distclean' should leave only the files that were in the + distribution. + +`mostlyclean' + Like `clean', but may refrain from deleting a few files that people + normally don't want to recompile. For example, the `mostlyclean' + target for GCC does not delete `libgcc.a', because recompiling it + is rarely necessary and takes a lot of time. + +`maintainer-clean' + Delete almost everything from the current directory that can be + reconstructed with this Makefile. This typically includes + everything deleted by `distclean', plus more: C source files + produced by Bison, tags tables, Info files, and so on. + + The reason we say "almost everything" is that running the command + `make maintainer-clean' should not delete `configure' even if + `configure' can be remade using a rule in the Makefile. More + generally, `make maintainer-clean' should not delete anything that + needs to exist in order to run `configure' and then begin to build + the program. This is the only exception; `maintainer-clean' should + delete everything else that can be rebuilt. + + The `maintainer-clean' target is intended to be used by a + maintainer of the package, not by ordinary users. You may need + special tools to reconstruct some of the files that `make + maintainer-clean' deletes. Since these files are normally + included in the distribution, we don't take care to make them easy + to reconstruct. If you find you need to unpack the full + distribution again, don't blame us. + + To help make users aware of this, the commands for the special + `maintainer-clean' target should start with these two: + + @echo 'This command is intended for maintainers to use; it' + @echo 'deletes files that may need special tools to rebuild.' + +`TAGS' + Update a tags table for this program. + +`info' + Generate any Info files needed. The best way to write the rules + is as follows: + + info: foo.info + + foo.info: foo.texi chap1.texi chap2.texi + $(MAKEINFO) $(srcdir)/foo.texi + + You must define the variable `MAKEINFO' in the Makefile. It should + run the `makeinfo' program, which is part of the Texinfo + distribution. + + Normally a GNU distribution comes with Info files, and that means + the Info files are present in the source directory. Therefore, + the Make rule for an info file should update it in the source + directory. When users build the package, ordinarily Make will not + update the Info files because they will already be up to date. + +`dvi' + Generate DVI files for all Texinfo documentation. For example: + + dvi: foo.dvi + + foo.dvi: foo.texi chap1.texi chap2.texi + $(TEXI2DVI) $(srcdir)/foo.texi + + You must define the variable `TEXI2DVI' in the Makefile. It should + run the program `texi2dvi', which is part of the Texinfo + distribution.(1) Alternatively, write just the dependencies, and + allow GNU `make' to provide the command. + +`dist' + Create a distribution tar file for this program. The tar file + should be set up so that the file names in the tar file start with + a subdirectory name which is the name of the package it is a + distribution for. This name can include the version number. + + For example, the distribution tar file of GCC version 1.40 unpacks + into a subdirectory named `gcc-1.40'. + + The easiest way to do this is to create a subdirectory + appropriately named, use `ln' or `cp' to install the proper files + in it, and then `tar' that subdirectory. + + Compress the tar file with `gzip'. For example, the actual + distribution file for GCC version 1.40 is called `gcc-1.40.tar.gz'. + + The `dist' target should explicitly depend on all non-source files + that are in the distribution, to make sure they are up to date in + the distribution. *Note Making Releases: Releases. + +`check' + Perform self-tests (if any). The user must build the program + before running the tests, but need not install the program; you + should write the self-tests so that they work when the program is + built but not installed. + + The following targets are suggested as conventional names, for +programs in which they are useful. + +`installcheck' + Perform installation tests (if any). The user must build and + install the program before running the tests. You should not + assume that `$(bindir)' is in the search path. + +`installdirs' + It's useful to add a target named `installdirs' to create the + directories where files are installed, and their parent + directories. There is a script called `mkinstalldirs' which is + convenient for this; you can find it in the Texinfo package. You + can use a rule like this: + + # Make sure all installation directories (e.g. $(bindir)) + # actually exist by making them if necessary. + installdirs: mkinstalldirs + $(srcdir)/mkinstalldirs $(bindir) $(datadir) \ + $(libdir) $(infodir) \ + $(mandir) + + or, if you wish to support `DESTDIR', + + # Make sure all installation directories (e.g. $(bindir)) + # actually exist by making them if necessary. + installdirs: mkinstalldirs + $(srcdir)/mkinstalldirs \ + $(DESTDIR)$(bindir) $(DESTDIR)$(datadir) \ + $(DESTDIR)$(libdir) $(DESTDIR)$(infodir) \ + $(DESTDIR)$(mandir) + + This rule should not modify the directories where compilation is + done. It should do nothing but create installation directories. + + ---------- Footnotes ---------- + + (1) `texi2dvi' uses TeX to do the real work of formatting. TeX is +not distributed with Texinfo. + + +File: standards.info, Node: Install Command Categories, Prev: Standard Targets, Up: Makefile Conventions + +7.2.6 Install Command Categories +-------------------------------- + +When writing the `install' target, you must classify all the commands +into three categories: normal ones, "pre-installation" commands and +"post-installation" commands. + + Normal commands move files into their proper places, and set their +modes. They may not alter any files except the ones that come entirely +from the package they belong to. + + Pre-installation and post-installation commands may alter other +files; in particular, they can edit global configuration files or data +bases. + + Pre-installation commands are typically executed before the normal +commands, and post-installation commands are typically run after the +normal commands. + + The most common use for a post-installation command is to run +`install-info'. This cannot be done with a normal command, since it +alters a file (the Info directory) which does not come entirely and +solely from the package being installed. It is a post-installation +command because it needs to be done after the normal command which +installs the package's Info files. + + Most programs don't need any pre-installation commands, but we have +the feature just in case it is needed. + + To classify the commands in the `install' rule into these three +categories, insert "category lines" among them. A category line +specifies the category for the commands that follow. + + A category line consists of a tab and a reference to a special Make +variable, plus an optional comment at the end. There are three +variables you can use, one for each category; the variable name +specifies the category. Category lines are no-ops in ordinary execution +because these three Make variables are normally undefined (and you +_should not_ define them in the makefile). + + Here are the three possible category lines, each with a comment that +explains what it means: + + $(PRE_INSTALL) # Pre-install commands follow. + $(POST_INSTALL) # Post-install commands follow. + $(NORMAL_INSTALL) # Normal commands follow. + + If you don't use a category line at the beginning of the `install' +rule, all the commands are classified as normal until the first category +line. If you don't use any category lines, all the commands are +classified as normal. + + These are the category lines for `uninstall': + + $(PRE_UNINSTALL) # Pre-uninstall commands follow. + $(POST_UNINSTALL) # Post-uninstall commands follow. + $(NORMAL_UNINSTALL) # Normal commands follow. + + Typically, a pre-uninstall command would be used for deleting entries +from the Info directory. + + If the `install' or `uninstall' target has any dependencies which +act as subroutines of installation, then you should start _each_ +dependency's commands with a category line, and start the main target's +commands with a category line also. This way, you can ensure that each +command is placed in the right category regardless of which of the +dependencies actually run. + + Pre-installation and post-installation commands should not run any +programs except for these: + + [ basename bash cat chgrp chmod chown cmp cp dd diff echo + egrep expand expr false fgrep find getopt grep gunzip gzip + hostname install install-info kill ldconfig ln ls md5sum + mkdir mkfifo mknod mv printenv pwd rm rmdir sed sort tee + test touch true uname xargs yes + + The reason for distinguishing the commands in this way is for the +sake of making binary packages. Typically a binary package contains +all the executables and other files that need to be installed, and has +its own method of installing them--so it does not need to run the normal +installation commands. But installing the binary package does need to +execute the pre-installation and post-installation commands. + + Programs to build binary packages work by extracting the +pre-installation and post-installation commands. Here is one way of +extracting the pre-installation commands: + + make -n install -o all \ + PRE_INSTALL=pre-install \ + POST_INSTALL=post-install \ + NORMAL_INSTALL=normal-install \ + | gawk -f pre-install.awk + +where the file `pre-install.awk' could contain this: + + $0 ~ /^\t[ \t]*(normal_install|post_install)[ \t]*$/ {on = 0} + on {print $0} + $0 ~ /^\t[ \t]*pre_install[ \t]*$/ {on = 1} + + The resulting file of pre-installation commands is executed as a +shell script as part of installing the binary package. + + +File: standards.info, Node: Releases, Prev: Makefile Conventions, Up: Managing Releases + +7.3 Making Releases +=================== + +Package the distribution of `Foo version 69.96' up in a gzipped tar +file with the name `foo-69.96.tar.gz'. It should unpack into a +subdirectory named `foo-69.96'. + + Building and installing the program should never modify any of the +files contained in the distribution. This means that all the files +that form part of the program in any way must be classified into "source +files" and "non-source files". Source files are written by humans and +never changed automatically; non-source files are produced from source +files by programs under the control of the Makefile. + + The distribution should contain a file named `README' which gives +the name of the package, and a general description of what it does. It +is also good to explain the purpose of each of the first-level +subdirectories in the package, if there are any. The `README' file +should either state the version number of the package, or refer to where +in the package it can be found. + + The `README' file should refer to the file `INSTALL', which should +contain an explanation of the installation procedure. + + The `README' file should also refer to the file which contains the +copying conditions. The GNU GPL, if used, should be in a file called +`COPYING'. If the GNU LGPL is used, it should be in a file called +`COPYING.LIB'. + + Naturally, all the source files must be in the distribution. It is +okay to include non-source files in the distribution, provided they are +up-to-date and machine-independent, so that building the distribution +normally will never modify them. We commonly include non-source files +produced by Bison, `lex', TeX, and `makeinfo'; this helps avoid +unnecessary dependencies between our distributions, so that users can +install whichever packages they want to install. + + Non-source files that might actually be modified by building and +installing the program should *never* be included in the distribution. +So if you do distribute non-source files, always make sure they are up +to date when you make a new distribution. + + Make sure that the directory into which the distribution unpacks (as +well as any subdirectories) are all world-writable (octal mode 777). +This is so that old versions of `tar' which preserve the ownership and +permissions of the files from the tar archive will be able to extract +all the files even if the user is unprivileged. + + Make sure that all the files in the distribution are world-readable. + + Make sure that no file name in the distribution is more than 14 +characters long. Likewise, no file created by building the program +should have a name longer than 14 characters. The reason for this is +that some systems adhere to a foolish interpretation of the POSIX +standard, and refuse to open a longer name, rather than truncating as +they did in the past. + + Don't include any symbolic links in the distribution itself. If the +tar file contains symbolic links, then people cannot even unpack it on +systems that don't support symbolic links. Also, don't use multiple +names for one file in different directories, because certain file +systems cannot handle this and that prevents unpacking the distribution. + + Try to make sure that all the file names will be unique on MS-DOS. A +name on MS-DOS consists of up to 8 characters, optionally followed by a +period and up to three characters. MS-DOS will truncate extra +characters both before and after the period. Thus, `foobarhacker.c' +and `foobarhacker.o' are not ambiguous; they are truncated to +`foobarha.c' and `foobarha.o', which are distinct. + + Include in your distribution a copy of the `texinfo.tex' you used to +test print any `*.texinfo' or `*.texi' files. + + Likewise, if your program uses small GNU software packages like +regex, getopt, obstack, or termcap, include them in the distribution +file. Leaving them out would make the distribution file a little +smaller at the expense of possible inconvenience to a user who doesn't +know what other files to get. + + +File: standards.info, Node: References, Next: Copying This Manual, Prev: Managing Releases, Up: Top + +8 References to Non-Free Software and Documentation +*************************************************** + +A GNU program should not recommend use of any non-free program. We +can't stop some people from writing proprietary programs, or stop other +people from using them, but we can and should avoid helping to +advertise them to new potential customers. Proprietary software is a +social and ethical problem, and the point of GNU is to solve that +problem. + + When a non-free program or system is well known, you can mention it +in passing--that is harmless, since users who might want to use it +probably already know about it. For instance, it is fine to explain +how to build your package on top of some non-free operating system, or +how to use it together with some widely used non-free program. + + However, you should give only the necessary information to help those +who already use the non-free program to use your program with it--don't +give, or refer to, any further information about the proprietary +program, and don't imply that the proprietary program enhances your +program, or that its existence is in any way a good thing. The goal +should be that people already using the proprietary program will get +the advice they need about how to use your free program, while people +who don't already use the proprietary program will not see anything to +lead them to take an interest in it. + + If a non-free program or system is obscure in your program's domain, +your program should not mention or support it at all, since doing so +would tend to popularize the non-free program more than it popularizes +your program. (You cannot hope to find many additional users among the +users of Foobar if the users of Foobar are few.) + + A GNU package should not refer the user to any non-free documentation +for free software. Free documentation that can be included in free +operating systems is essential for completing the GNU system, so it is +a major focus of the GNU Project; to recommend use of documentation +that we are not allowed to use in GNU would undermine the efforts to +get documentation that we can include. So GNU packages should never +recommend non-free documentation. + + +File: standards.info, Node: Copying This Manual, Next: Index, Prev: References, Up: Top + +Annexe A Copying This Manual +**************************** + +* Menu: + +* GNU Free Documentation License:: License for copying this manual + + +File: standards.info, Node: GNU Free Documentation License, Up: Copying This Manual + +Annexe B GNU Free Documentation License +*************************************** + + Version 1.1, March 2000 + + Copyright (C) 2000 Free Software Foundation, Inc. + 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA + + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + + 0. PREAMBLE + + The purpose of this License is to make a manual, textbook, or other + written document "free" in the sense of freedom: to assure everyone + the effective freedom to copy and redistribute it, with or without + modifying it, either commercially or noncommercially. Secondarily, + this License preserves for the author and publisher a way to get + credit for their work, while not being considered responsible for + modifications made by others. + + This License is a kind of "copyleft", which means that derivative + works of the document must themselves be free in the same sense. + It complements the GNU General Public License, which is a copyleft + license designed for free software. + + We have designed this License in order to use it for manuals for + free software, because free software needs free documentation: a + free program should come with manuals providing the same freedoms + that the software does. But this License is not limited to + software manuals; it can be used for any textual work, regardless + of subject matter or whether it is published as a printed book. + We recommend this License principally for works whose purpose is + instruction or reference. + + + 1. APPLICABILITY AND DEFINITIONS + + This License applies to any manual or other work that contains a + notice placed by the copyright holder saying it can be distributed + under the terms of this License. The "Document", below, refers to + any such manual or work. Any member of the public is a licensee, + and is addressed as "you." + + A "Modified Version" of the Document means any work containing the + Document or a portion of it, either copied verbatim, or with + modifications and/or translated into another language. + + A "Secondary Section" is a named appendix or a front-matter + section of the Document that deals exclusively with the + relationship of the publishers or authors of the Document to the + Document's overall subject (or to related matters) and contains + nothing that could fall directly within that overall subject. + (For example, if the Document is in part a textbook of + mathematics, a Secondary Section may not explain any mathematics.) + The relationship could be a matter of historical connection with + the subject or with related matters, or of legal, commercial, + philosophical, ethical or political position regarding them. + + The "Invariant Sections" are certain Secondary Sections whose + titles are designated, as being those of Invariant Sections, in + the notice that says that the Document is released under this + License. + + The "Cover Texts" are certain short passages of text that are + listed, as Front-Cover Texts or Back-Cover Texts, in the notice + that says that the Document is released under this License. + + A "Transparent" copy of the Document means a machine-readable copy, + represented in a format whose specification is available to the + general public, whose contents can be viewed and edited directly + and straightforwardly with generic text editors or (for images + composed of pixels) generic paint programs or (for drawings) some + widely available drawing editor, and that is suitable for input to + text formatters or for automatic translation to a variety of + formats suitable for input to text formatters. A copy made in an + otherwise Transparent file format whose markup has been designed + to thwart or discourage subsequent modification by readers is not + Transparent. A copy that is not "Transparent" is called "Opaque." + + Examples of suitable formats for Transparent copies include plain + ASCII without markup, Texinfo input format, LaTeX input format, + SGML or XML using a publicly available DTD, and + standard-conforming simple HTML designed for human modification. + Opaque formats include PostScript, PDF, proprietary formats that + can be read and edited only by proprietary word processors, SGML + or XML for which the DTD and/or processing tools are not generally + available, and the machine-generated HTML produced by some word + processors for output purposes only. + + The "Title Page" means, for a printed book, the title page itself, + plus such following pages as are needed to hold, legibly, the + material this License requires to appear in the title page. For + works in formats which do not have any title page as such, "Title + Page" means the text near the most prominent appearance of the + work's title, preceding the beginning of the body of the text. + + 2. VERBATIM COPYING + + You may copy and distribute the Document in any medium, either + commercially or noncommercially, provided that this License, the + copyright notices, and the license notice saying this License + applies to the Document are reproduced in all copies, and that you + add no other conditions whatsoever to those of this License. You + may not use technical measures to obstruct or control the reading + or further copying of the copies you make or distribute. However, + you may accept compensation in exchange for copies. If you + distribute a large enough number of copies you must also follow + the conditions in section 3. + + You may also lend copies, under the same conditions stated above, + and you may publicly display copies. + + 3. COPYING IN QUANTITY + + If you publish printed copies of the Document numbering more than + 100, and the Document's license notice requires Cover Texts, you + must enclose the copies in covers that carry, clearly and legibly, + all these Cover Texts: Front-Cover Texts on the front cover, and + Back-Cover Texts on the back cover. Both covers must also clearly + and legibly identify you as the publisher of these copies. The + front cover must present the full title with all words of the + title equally prominent and visible. You may add other material + on the covers in addition. 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If you use the + latter option, you must take reasonably prudent steps, when you + begin distribution of Opaque copies in quantity, to ensure that + this Transparent copy will remain thus accessible at the stated + location until at least one year after the last time you + distribute an Opaque copy (directly or through your agents or + retailers) of that edition to the public. + + It is requested, but not required, that you contact the authors of + the Document well before redistributing any large number of + copies, to give them a chance to provide you with an updated + version of the Document. + + 4. MODIFICATIONS + + You may copy and distribute a Modified Version of the Document + under the conditions of sections 2 and 3 above, provided that you + release the Modified Version under precisely this License, with + the Modified Version filling the role of the Document, thus + licensing distribution and modification of the Modified Version to + whoever possesses a copy of it. In addition, you must do these + things in the Modified Version: + + A. Use in the Title Page (and on the covers, if any) a title + distinct from that of the Document, and from those of previous + versions (which should, if there were any, be listed in the + History section of the Document). You may use the same title + as a previous version if the original publisher of that version + gives permission. + B. List on the Title Page, as authors, one or more persons or + entities responsible for authorship of the modifications in the + Modified Version, together with at least five of the principal + authors of the Document (all of its principal authors, if it + has less than five). + C. State on the Title page the name of the publisher of the + Modified Version, as the publisher. + D. Preserve all the copyright notices of the Document. + E. Add an appropriate copyright notice for your modifications + adjacent to the other copyright notices. + F. Include, immediately after the copyright notices, a license + notice giving the public permission to use the Modified Version + under the terms of this License, in the form shown in the + Addendum below. + G. Preserve in that license notice the full lists of Invariant + Sections and required Cover Texts given in the Document's + license notice. + H. Include an unaltered copy of this License. + I. Preserve the section entitled "History", and its title, and add + to it an item stating at least the title, year, new authors, and + publisher of the Modified Version as given on the Title Page. If + there is no section entitled "History" in the Document, create + one stating the title, year, authors, and publisher of the + Document as given on its Title Page, then add an item + describing the Modified Version as stated in the previous + sentence. + J. Preserve the network location, if any, given in the Document for + public access to a Transparent copy of the Document, and likewise + the network locations given in the Document for previous versions + it was based on. These may be placed in the "History" section. + You may omit a network location for a work that was published at + least four years before the Document itself, or if the original + publisher of the version it refers to gives permission. + K. In any section entitled "Acknowledgements" or "Dedications", + preserve the section's title, and preserve in the section all the + substance and tone of each of the contributor acknowledgements + and/or dedications given therein. + L. Preserve all the Invariant Sections of the Document, + unaltered in their text and in their titles. Section numbers + or the equivalent are not considered part of the section titles. + M. Delete any section entitled "Endorsements." Such a section + may not be included in the Modified Version. + N. Do not retitle any existing section as "Endorsements" or to + conflict in title with any Invariant Section. + + If the Modified Version includes new front-matter sections or + appendices that qualify as Secondary Sections and contain no + material copied from the Document, you may at your option + designate some or all of these sections as invariant. To do this, + add their titles to the list of Invariant Sections in the Modified + Version's license notice. These titles must be distinct from any + other section titles. + + You may add a section entitled "Endorsements", provided it contains + nothing but endorsements of your Modified Version by various + parties-for example, statements of peer review or that the text has + been approved by an organization as the authoritative definition + of a standard. + + You may add a passage of up to five words as a Front-Cover Text, + and a passage of up to 25 words as a Back-Cover Text, to the end + of the list of Cover Texts in the Modified Version. Only one + passage of Front-Cover Text and one of Back-Cover Text may be + added by (or through arrangements made by) any one entity. If the + Document already includes a cover text for the same cover, + previously added by you or by arrangement made by the same entity + you are acting on behalf of, you may not add another; but you may + replace the old one, on explicit permission from the previous + publisher that added the old one. + + The author(s) and publisher(s) of the Document do not by this + License give permission to use their names for publicity for or to + assert or imply endorsement of any Modified Version. + + 5. COMBINING DOCUMENTS + + You may combine the Document with other documents released under + this License, under the terms defined in section 4 above for + modified versions, provided that you include in the combination + all of the Invariant Sections of all of the original documents, + unmodified, and list them all as Invariant Sections of your + combined work in its license notice. + + The combined work need only contain one copy of this License, and + multiple identical Invariant Sections may be replaced with a single + copy. If there are multiple Invariant Sections with the same name + but different contents, make the title of each such section unique + by adding at the end of it, in parentheses, the name of the + original author or publisher of that section if known, or else a + unique number. Make the same adjustment to the section titles in + the list of Invariant Sections in the license notice of the + combined work. + + In the combination, you must combine any sections entitled + "History" in the various original documents, forming one section + entitled "History"; likewise combine any sections entitled + "Acknowledgements", and any sections entitled "Dedications." You + must delete all sections entitled "Endorsements." + + 6. COLLECTIONS OF DOCUMENTS + + You may make a collection consisting of the Document and other + documents released under this License, and replace the individual + copies of this License in the various documents with a single copy + that is included in the collection, provided that you follow the + rules of this License for verbatim copying of each of the + documents in all other respects. + + You may extract a single document from such a collection, and + distribute it individually under this License, provided you insert + a copy of this License into the extracted document, and follow + this License in all other respects regarding verbatim copying of + that document. + + 7. AGGREGATION WITH INDEPENDENT WORKS + + A compilation of the Document or its derivatives with other + separate and independent documents or works, in or on a volume of + a storage or distribution medium, does not as a whole count as a + Modified Version of the Document, provided no compilation + copyright is claimed for the compilation. Such a compilation is + called an "aggregate", and this License does not apply to the + other self-contained works thus compiled with the Document, on + account of their being thus compiled, if they are not themselves + derivative works of the Document. + + If the Cover Text requirement of section 3 is applicable to these + copies of the Document, then if the Document is less than one + quarter of the entire aggregate, the Document's Cover Texts may be + placed on covers that surround only the Document within the + aggregate. Otherwise they must appear on covers around the whole + aggregate. + + 8. TRANSLATION + + Translation is considered a kind of modification, so you may + distribute translations of the Document under the terms of section + 4. Replacing Invariant Sections with translations requires special + permission from their copyright holders, but you may include + translations of some or all Invariant Sections in addition to the + original versions of these Invariant Sections. You may include a + translation of this License provided that you also include the + original English version of this License. In case of a + disagreement between the translation and the original English + version of this License, the original English version will prevail. + + 9. TERMINATION + + You may not copy, modify, sublicense, or distribute the Document + except as expressly provided for under this License. Any other + attempt to copy, modify, sublicense or distribute the Document is + void, and will automatically terminate your rights under this + License. However, parties who have received copies, or rights, + from you under this License will not have their licenses + terminated so long as such parties remain in full compliance. + + 10. FUTURE REVISIONS OF THIS LICENSE + + The Free Software Foundation may publish new, revised versions of + the GNU Free Documentation License from time to time. Such new + versions will be similar in spirit to the present version, but may + differ in detail to address new problems or concerns. See + http://www.gnu.org/copyleft/. + + Each version of the License is given a distinguishing version + number. If the Document specifies that a particular numbered + version of this License "or any later version" applies to it, you + have the option of following the terms and conditions either of + that specified version or of any later version that has been + published (not as a draft) by the Free Software Foundation. If + the Document does not specify a version number of this License, + you may choose any version ever published (not as a draft) by the + Free Software Foundation. + + +ADDENDUM: How to use this License for your documents +==================================================== + +To use this License in a document you have written, include a copy of +the License in the document and put the following copyright and license +notices just after the title page: + + Copyright (C) YEAR YOUR NAME. + Permission is granted to copy, distribute and/or modify this document + under the terms of the GNU Free Documentation License, Version 1.1 + or any later version published by the Free Software Foundation; + with the Invariant Sections being LIST THEIR TITLES, with the + Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. + A copy of the license is included in the section entitled "GNU + Free Documentation License." + + If you have no Invariant Sections, write "with no Invariant Sections" +instead of saying which ones are invariant. If you have no Front-Cover +Texts, write "no Front-Cover Texts" instead of "Front-Cover Texts being +LIST"; likewise for Back-Cover Texts. + + If your document contains nontrivial examples of program code, we +recommend releasing these examples in parallel under your choice of +free software license, such as the GNU General Public License, to +permit their use in free software. + + +File: standards.info, Node: Index, Prev: Copying This Manual, Up: Top + +Index +***** + + +* Menu: + +* #endif, commenting: Comments. (line 54) +* --help option: Command-Line Interfaces. + (line 119) +* --version option: Command-Line Interfaces. + (line 34) +* -Wall compiler option: Syntactic Conventions. + (line 10) +* accepting contributions: Contributions. (line 6) +* address for bug reports: Command-Line Interfaces. + (line 125) +* ANSI C standard: Standard C. (line 6) +* arbitrary limits on data: Semantics. (line 6) +* autoconf: System Portability. (line 23) +* avoiding proprietary code: Reading Non-Free Code. + (line 6) +* behavior, dependent on program's name: User Interfaces. (line 6) +* binary packages: Install Command Categories. + (line 80) +* bindir: Directory Variables. (line 45) +* braces, in C source: Formatting. (line 6) +* bug reports: Command-Line Interfaces. + (line 125) +* canonical name of a program: Command-Line Interfaces. + (line 41) +* casting pointers to integers: CPU Portability. (line 67) +* change logs: Change Logs. (line 6) +* change logs, conditional changes: Conditional Changes. (line 6) +* change logs, style: Style of Change Logs. + (line 6) +* command-line arguments, decoding: Semantics. (line 46) +* command-line interface: Command-Line Interfaces. + (line 6) +* commenting: Comments. (line 6) +* compatibility with C and POSIX standards: Compatibility. (line 6) +* compiler warnings: Syntactic Conventions. + (line 10) +* conditional changes, and change logs: Conditional Changes. (line 6) +* conditionals, comments for: Comments. (line 54) +* configure: Configuration. (line 6) +* control-L: Formatting. (line 114) +* conventions for makefiles: Makefile Conventions. + (line 6) +* corba: Graphical Interfaces. + (line 16) +* credits for manuals: Manual Credits. (line 6) +* data types, and portability: CPU Portability. (line 6) +* declaration for system functions: System Functions. (line 21) +* documentation: Documentation. (line 6) +* doschk: Names. (line 38) +* downloading this manual: Preface. (line 17) +* error messages: Semantics. (line 19) +* error messages, formatting: Errors. (line 6) +* exec_prefix: Directory Variables. (line 27) +* expressions, splitting: Formatting. (line 77) +* file usage: File Usage. (line 6) +* file-name limitations: Names. (line 38) +* formatting error messages: Errors. (line 6) +* formatting source code: Formatting. (line 6) +* formfeed: Formatting. (line 114) +* function argument, declaring: Syntactic Conventions. + (line 6) +* function prototypes: Standard C. (line 17) +* getopt: Command-Line Interfaces. + (line 6) +* gettext: Internationalization. + (line 6) +* gnome: Graphical Interfaces. + (line 16) +* graphical user interface: Graphical Interfaces. + (line 6) +* gtk: Graphical Interfaces. + (line 6) +* GUILE: Source Language. (line 38) +* implicit int: Syntactic Conventions. + (line 6) +* impossible conditions: Semantics. (line 70) +* internationalization: Internationalization. + (line 6) +* legal aspects: Legal Issues. (line 6) +* legal papers: Contributions. (line 6) +* libexecdir: Directory Variables. (line 58) +* libraries: Libraries. (line 6) +* library functions, and portability: System Functions. (line 6) +* license for manuals: License for Manuals. (line 6) +* lint: Syntactic Conventions. + (line 109) +* long option names: Option Table. (line 6) +* long-named options: Command-Line Interfaces. + (line 12) +* makefile, conventions for: Makefile Conventions. + (line 6) +* malloc return value: Semantics. (line 25) +* man pages: Man Pages. (line 6) +* manual structure: Manual Structure Details. + (line 6) +* memory allocation failure: Semantics. (line 25) +* memory usage: Memory Usage. (line 6) +* message text, and internationalization: Internationalization. + (line 29) +* mmap: Mmap. (line 6) +* multiple variables in a line: Syntactic Conventions. + (line 35) +* names of variables, functions, and files: Names. (line 6) +* NEWS file: NEWS File. (line 6) +* non-POSIX systems, and portability: System Portability. (line 32) +* non-standard extensions: Using Extensions. (line 6) +* NUL characters: Semantics. (line 11) +* open brace: Formatting. (line 6) +* optional features, configure-time: Configuration. (line 76) +* options for compatibility: Compatibility. (line 14) +* output device and program's behavior: User Interfaces. (line 13) +* packaging: Releases. (line 6) +* portability, and data types: CPU Portability. (line 6) +* portability, and library functions: System Functions. (line 6) +* portability, between system types: System Portability. (line 6) +* POSIX compatibility: Compatibility. (line 6) +* POSIXLY_CORRECT, environment variable: Compatibility. (line 21) +* post-installation commands: Install Command Categories. + (line 6) +* pre-installation commands: Install Command Categories. + (line 6) +* prefix: Directory Variables. (line 17) +* program configuration: Configuration. (line 6) +* program design: Design Advice. (line 6) +* program name and its behavior: User Interfaces. (line 6) +* program's canonical name: Command-Line Interfaces. + (line 41) +* programming languges: Source Language. (line 6) +* proprietary programs: Reading Non-Free Code. + (line 6) +* README file: Releases. (line 17) +* references to non-free material: References. (line 6) +* releasing: Managing Releases. (line 6) +* sbindir: Directory Variables. (line 51) +* signal handling: Semantics. (line 59) +* spaces before open-paren: Formatting. (line 71) +* standard command-line options: Command-Line Interfaces. + (line 31) +* standards for makefiles: Makefile Conventions. + (line 6) +* string library functions: System Functions. (line 55) +* syntactic conventions: Syntactic Conventions. + (line 6) +* table of long options: Option Table. (line 6) +* temporary files: Semantics. (line 84) +* temporary variables: Syntactic Conventions. + (line 23) +* texinfo.tex, in a distribution: Releases. (line 73) +* TMPDIR environment variable: Semantics. (line 84) +* trademarks: Trademarks. (line 6) +* where to obtain standards.texi: Preface. (line 17) + + + +Tag Table: +Node: Top712 +Node: Preface1412 +Node: Legal Issues3632 +Node: Reading Non-Free Code4096 +Node: Contributions5824 +Node: Trademarks7978 +Node: Design Advice9041 +Node: Source Language9625 +Node: Compatibility11637 +Node: Using Extensions13265 +Node: Standard C14841 +Node: Conditional Compilation17244 +Node: Program Behavior18543 +Node: Semantics19462 +Node: Libraries24155 +Node: Errors25400 +Node: User Interfaces27181 +Node: Graphical Interfaces28786 +Node: Command-Line Interfaces29821 +Node: Option Table35892 +Node: Memory Usage50901 +Node: File Usage51926 +Node: Writing C52674 +Node: Formatting53524 +Node: Comments57587 +Node: Syntactic Conventions60889 +Node: Names64301 +Node: System Portability66510 +Node: CPU Portability68895 +Node: System Functions72151 +Node: Internationalization77348 +Node: Mmap80501 +Node: Documentation81211 +Node: GNU Manuals82316 +Node: Doc Strings and Manuals87373 +Node: Manual Structure Details88926 +Node: License for Manuals90344 +Node: Manual Credits91318 +Node: Printed Manuals91711 +Node: NEWS File92397 +Node: Change Logs93075 +Node: Change Log Concepts93829 +Node: Style of Change Logs95693 +Node: Simple Changes97728 +Node: Conditional Changes98972 +Node: Indicating the Part Changed100394 +Node: Man Pages100921 +Node: Reading other Manuals102545 +Node: Managing Releases103336 +Node: Configuration104099 +Node: Makefile Conventions111004 +Node: Makefile Basics111810 +Node: Utilities in Makefiles114984 +Node: Command Variables117129 +Node: Directory Variables120706 +Node: Standard Targets131600 +Ref: Standard Targets-Footnote-1142840 +Node: Install Command Categories142940 +Node: Releases147522 +Node: References151610 +Node: Copying This Manual153895 +Node: GNU Free Documentation License154127 +Node: Index173812 + +End Tag Table |