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| author | Andrew Cagney <cagney@redhat.com> | 2002-02-27 02:13:36 +0000 |
|---|---|---|
| committer | Andrew Cagney <cagney@redhat.com> | 2002-02-27 02:13:36 +0000 |
| commit | bd48e1a994cfacea33d2b7d3d96052a3af51736c (patch) | |
| tree | efef9ad255b16623d7fc5121950f07373e094024 /etc | |
| parent | 81a9a963a1d5374ada16859384e378b5561f4b2a (diff) | |
| download | binutils-gdb-bd48e1a994cfacea33d2b7d3d96052a3af51736c.tar.gz | |
* standards.texi: Import February 14, 2002 version.
* make-stds.texi: Import 2001 version.
* Makefile.in (install): Depend on install-info.
Diffstat (limited to 'etc')
| -rw-r--r-- | etc/ChangeLog | 5 | ||||
| -rw-r--r-- | etc/make-stds.texi | 81 | ||||
| -rw-r--r-- | etc/standards.texi | 1175 |
3 files changed, 978 insertions, 283 deletions
diff --git a/etc/ChangeLog b/etc/ChangeLog index ffd021f53fa..daf3a8b26f1 100644 --- a/etc/ChangeLog +++ b/etc/ChangeLog @@ -1,3 +1,8 @@ +2002-02-24 Andrew Cagney <ac131313@redhat.com> + + * standards.texi: Import February 14, 2002 version. + * make-stds.texi: Import 2001 version. + 2002-01-26 Hans-Peter Nilsson <hp@bitrange.com> * Makefile.in (install): Depend on install-info. diff --git a/etc/make-stds.texi b/etc/make-stds.texi index 2149764b8e9..250867adfcd 100644 --- a/etc/make-stds.texi +++ b/etc/make-stds.texi @@ -8,6 +8,17 @@ @cindex conventions for makefiles @cindex standards for makefiles +@c Copyright 1992, 1993, 1994, 1995, 1996, 1997, 1998, 2000, 2001 Free +@c Software Foundation, Inc. + +@c Permission is granted to copy, distribute and/or modify this document +@c under the terms of the GNU Free Documentation License, Version 1.1 +@c or any later version published by the Free Software Foundation; +@c with no Invariant Sections, with no +@c Front-Cover Texts, and with no Back-Cover Texts. +@c A copy of the license is included in the section entitled ``GNU +@c Free Documentation License''. + This @ifinfo node @@ -21,13 +32,15 @@ chapter @end ifclear @end iftex 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 +* 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. @end menu @@ -79,7 +92,7 @@ foo.1 : foo.man sedscript @noindent will fail when the build directory is not the source directory, because -@file{foo.man} and @file{sedscript} are in the the source directory. +@file{foo.man} and @file{sedscript} are in the source directory. When using GNU @code{make}, relying on @samp{VPATH} to find the source file will work in the case where there is a single dependency file, @@ -138,7 +151,7 @@ installation should not use any utilities directly except these: @c dd find @c gunzip gzip md5sum -@c mkfifo mknod tee uname +@c mkfifo mknod tee uname @example cat cmp cp diff echo egrep expr false grep install-info @@ -247,9 +260,10 @@ Every Makefile should define the variable @code{INSTALL}, which is the basic command for installing a file into the system. Every Makefile should also define the variables @code{INSTALL_PROGRAM} -and @code{INSTALL_DATA}. (The default for each of these should be -@code{$(INSTALL)}.) Then it should use those variables as the commands -for actual installation, for executables and nonexecutables +and @code{INSTALL_DATA}. (The default for @code{INSTALL_PROGRAM} should +be @code{$(INSTALL)}; the default for @code{INSTALL_DATA} should be +@code{$@{INSTALL@} -m 644}.) Then it should use those variables as the +commands for actual installation, for executables and nonexecutables respectively. Use these variables as follows: @example @@ -280,26 +294,28 @@ installed. Installation directories should always be named by variables, so it is easy to install in a nonstandard place. The standard names for these variables are described below. They are based on a standard filesystem -layout; variants of it are used in SVR4, 4.4BSD, Linux, Ultrix v4, and -other modern operating systems. +layout; variants of it are used in SVR4, 4.4BSD, GNU/Linux, Ultrix v4, +and other modern operating systems. These two variables set the root for the installation. All the other installation directories should be subdirectories of one of these two, and nothing should be directly installed into these two directories. -@table @samp +@table @code @item prefix +@vindex prefix A prefix used in constructing the default values of the variables listed below. The default value of @code{prefix} should be @file{/usr/local}. When building the complete GNU system, the prefix will be empty and @file{/usr} will be a symbolic link to @file{/}. (If you are using Autoconf, write it as @samp{@@prefix@@}.) -Running @samp{make install} with a different value of @code{prefix} -from the one used to build the program should @var{not} recompile -the program. +Running @samp{make install} with a different value of @code{prefix} from +the one used to build the program should @emph{not} recompile the +program. @item exec_prefix +@vindex exec_prefix A prefix used in constructing the default values of some of the variables listed below. The default value of @code{exec_prefix} should be @code{$(prefix)}. @@ -310,20 +326,22 @@ machine-specific files (such as executables and subroutine libraries), while @code{$(prefix)} is used directly for other directories. Running @samp{make install} with a different value of @code{exec_prefix} -from the one used to build the program should @var{not} recompile the +from the one used to build the program should @emph{not} recompile the program. @end table Executable programs are installed in one of the following directories. -@table @samp +@table @code @item bindir +@vindex bindir The directory for installing executable programs that users can run. This should normally be @file{/usr/local/bin}, but write it as @file{$(exec_prefix)/bin}. (If you are using Autoconf, write it as @samp{@@bindir@@}.) @item sbindir +@vindex 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 @file{/usr/local/sbin}, but write it as @@ -331,6 +349,7 @@ should normally be @file{/usr/local/sbin}, but write it as (If you are using Autoconf, write it as @samp{@@sbindir@@}.) @item libexecdir +@vindex libexecdir @comment This paragraph adjusted to avoid overfull hbox --roland 5jul94 The directory for installing executable programs to be run by other programs rather than by users. This directory should normally be @@ -623,7 +642,8 @@ the installation commands. @xref{Install Command Categories}. @item install-strip Like @code{install}, but strip the executable files while installing -them. In many cases, the definition of this target can be very simple: +them. In simple cases, this target can use the @code{install} target in +a simple way: @smallexample install-strip: @@ -631,6 +651,14 @@ install-strip: install @end smallexample +But if the package installs scripts as well as real executables, the +@code{install-strip} target can't just refer to the @code{install} +target; it has to strip the executables but not the scripts. + +@code{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 @@ -745,7 +773,7 @@ The easiest way to do this is to create a subdirectory appropriately named, use @code{ln} or @code{cp} to install the proper files in it, and then @code{tar} that subdirectory. -Compress the tar file file with @code{gzip}. For example, the actual +Compress the tar file with @code{gzip}. For example, the actual distribution file for GCC version 1.40 is called @file{gcc-1.40.tar.gz}. The @code{dist} target should explicitly depend on all non-source files @@ -793,6 +821,19 @@ installdirs: mkinstalldirs $(mandir) @end smallexample +@noindent +or, if you wish to support @env{DESTDIR}, + +@smallexample +# 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) +@end smallexample + This rule should not modify the directories where compilation is done. It should do nothing but create installation directories. @end table diff --git a/etc/standards.texi b/etc/standards.texi index 910bf8b0479..5aa508e0184 100644 --- a/etc/standards.texi +++ b/etc/standards.texi @@ -3,7 +3,7 @@ @setfilename standards.info @settitle GNU Coding Standards @c This date is automagically updated when you save this file: -@set lastupdate March 13, 1998 +@set lastupdate February 14, 2002 @c %**end of header @ifinfo @@ -17,6 +17,12 @@ END-INFO-DIR-ENTRY @c @setchapternewpage odd @setchapternewpage off +@c Put everything in one index (arbitrarily chosen to be the concept index). +@syncodeindex fn cp +@syncodeindex ky cp +@syncodeindex pg cp +@syncodeindex vr cp + @c This is used by a cross ref in make-stds.texi @set CODESTD 1 @iftex @@ -28,52 +34,33 @@ END-INFO-DIR-ENTRY @ifinfo GNU Coding Standards -Copyright (C) 1992, 1993, 1994, 1995, 1996, 1997, 1998 Free Software Foundation, Inc. - -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. - -@ignore -Permission is granted to process this file through TeX and print the -results, provided the printed document carries copying permission -notice identical to this one except for the removal of this paragraph -(this paragraph not being relevant to the printed manual). -@end ignore - -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 Free Software Foundation. +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''. @end ifinfo @titlepage @title GNU Coding Standards -@author Richard Stallman +@author Richard Stallman, et al. @author last updated @value{lastupdate} @page @vskip 0pt plus 1filll -Copyright @copyright{} 1992, 1993, 1994, 1995, 1996, 1997, 1998 Free Software Foundation, Inc. - -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 Free Software Foundation. +Copyright @copyright{} 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''. @end titlepage @ifinfo @@ -85,12 +72,16 @@ Last updated @value{lastupdate}. @menu * Preface:: About the GNU Coding Standards -* Intellectual Property:: Keeping Free Software Free +* 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:: + @end menu @node Preface @@ -104,28 +95,57 @@ 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 +@value{lastupdate}. + +@cindex where to obtain @code{standards.texi} +@cindex downloading this manual +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 +@file{/pub/gnu/standards/}. The GNU Coding Standards are available +there in several different formats: @file{standards.text}, +@file{standards.info}, and @file{standards.dvi}, as well as the +Texinfo ``source'' which is divided in two files: +@file{standards.texi} and @file{make-stds.texi}. The GNU Coding +Standards are also available on the GNU World Wide Web server: +@uref{http://www.gnu.org/prep/standards_toc.html}. + Corrections or suggestions for this document should be sent to -@email{gnu@@gnu.org}. If you make a suggestion, please include a +@email{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 @file{standards.texi} or @file{make-stds.texi} files, but if you don't have those files, please mail your suggestion anyway. -This release of the GNU Coding Standards was last updated -@value{lastupdate}. +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. -@node Intellectual Property +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. + +@node Legal Issues @chapter Keeping Free Software Free +@cindex legal aspects This @value{CHAPTER} discusses how you can make sure that GNU software -remains unencumbered. +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 @end menu @node Reading Non-Free Code @section Referring to Proprietary Programs +@cindex proprietary programs +@cindex avoiding proprietary code Don't in any circumstances refer to Unix source code for or during your work on GNU! (Or to any other proprietary programs.) @@ -157,15 +177,17 @@ 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. - @node Contributions @section Accepting Contributions - -If someone else sends you a piece of code to add to the program you are -working on, we need legal papers to use it---the same sort of legal -papers we will need to get from you. @emph{Each} significant -contributor 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 +@cindex legal papers +@cindex 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. @emph{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 @@ -181,16 +203,17 @@ 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 you write a different solution to the -problem, you don't need to get papers. - -We know this is frustrating; 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! +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 @@ -200,39 +223,124 @@ 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. +@node Trademarks +@section Trademarks +@cindex 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. + @node Design Advice @chapter General Program Design +@cindex program design This @value{CHAPTER} discusses some of the issues you should take into account when designing your program. +@c Standard or ANSI C +@c +@c In 1989 the American National Standards Institute (ANSI) standardized +@c C as standard X3.159-1989. In December of that year the +@c International Standards Organization ISO adopted the ANSI C standard +@c making minor changes. In 1990 ANSI then re-adopted ISO standard +@c C. This version of C is known as either ANSI C or Standard C. + +@c A major revision of the C Standard appeared in 1999. + @menu +* Source Language:: Which languges to use. * Compatibility:: Compatibility with other implementations * Using Extensions:: Using non-standard features -* ANSI C:: Using ANSI C features -* Source Language:: Using languages other than C +* Standard C:: Using Standard C features +* Conditional Compilation:: Compiling Code Only If A Conditional is True @end menu +@node Source Language +@section Which Languages to Use +@cindex programming languges + +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: + +@itemize @bullet +@item +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. + +@item +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. +@end itemize + +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. + +@cindex GUILE +The standard extensibility interpreter for GNU software is GUILE, which +implements the language Scheme (an especially clean and simple dialect +of Lisp). @uref{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. + @node Compatibility @section Compatibility with Other Implementations +@cindex compatibility with C and @sc{posix} standards +@cindex @sc{posix} compatibility With occasional exceptions, utility programs and libraries for GNU should be upward compatible with those in Berkeley Unix, and upward -compatible with @sc{ansi} C if @sc{ansi} C specifies their behavior, and -upward compatible with @sc{POSIX} if @sc{POSIX} specifies their -behavior. +compatible with Standard C if Standard C specifies their +behavior, and upward compatible with @sc{posix} if @sc{posix} specifies +their behavior. When these standards conflict, it is useful to offer compatibility modes for each of them. -@sc{ansi} C and @sc{POSIX} prohibit many kinds of extensions. Feel free -to make the extensions anyway, and include a @samp{--ansi}, +@cindex options for compatibility +Standard C and @sc{posix} prohibit many kinds of extensions. Feel +free to make the extensions anyway, and include a @samp{--ansi}, @samp{--posix}, or @samp{--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. Try to -redesign its interface. +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 +@cindex @code{POSIXLY_CORRECT}, environment variable +Many GNU programs suppress extensions that conflict with @sc{posix} if the environment variable @code{POSIXLY_CORRECT} is defined (even if it is defined with a null value). Please make your program recognize this variable if appropriate. @@ -243,10 +351,12 @@ completely with something totally different and better. (For example, @code{vi} is replaced with Emacs.) But it is nice to offer a compatible feature as well. (There is a free @code{vi} clone, so we offer it.) -Additional useful features not in Berkeley Unix are welcome. +Additional useful features are welcome regardless of whether +there is any precedent for them. @node Using Extensions @section Using Non-standard Features +@cindex non-standard extensions Many GNU facilities that already exist support a number of convenient extensions over the comparable Unix facilities. Whether to use these @@ -267,29 +377,33 @@ 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. Such programs would -be broken by use of GNU extensions. +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. -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 no good. +@node Standard C +@section Standard C and Pre-Standard C +@cindex @sc{ansi} C standard -@node ANSI C -@section @sc{ansi} C and pre-@sc{ansi} 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. -Do not ever use the ``trigraph'' feature of @sc{ansi} 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. -@sc{ansi} C is widespread enough now that it is ok to write new programs -that use @sc{ansi} C features (and therefore will not work in -non-@sc{ansi} compilers). And if a program is already written in -@sc{ansi} C, there's no need to convert it to support non-@sc{ansi} -compilers. +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. -However, it is easy to support non-@sc{ansi} compilers in most programs, -so you might still consider doing so when you write a program. Instead -of writing function definitions in @sc{ansi} prototype form, +@cindex function prototypes +To support pre-standard C, instead of writing function definitions in +standard prototype form, @example int @@ -298,7 +412,7 @@ foo (int x, int y) @end example @noindent -write the definition in pre-@sc{ansi} style like this, +write the definition in pre-standard style like this, @example int @@ -315,79 +429,123 @@ int foo (int, int); @end example You need such a declaration anyway, in a header file, to get the benefit -of @sc{ansi} C prototypes in all the files where the function is called. -And once you have it, you lose nothing by writing the function -definition in the pre-@sc{ansi} style. +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 @code{int}. +If you think of an argument as being of a type narrower than @code{int}, +declare it as @code{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 +@code{dev_t}, you run into trouble, because @code{dev_t} is shorter than +@code{int} on some machines; but you cannot use @code{int} instead, +because @code{dev_t} is wider than @code{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 @code{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: -If you don't know non-@sc{ansi} C, there's no need to learn it; just -write in @sc{ansi} C. +@example +/* Declare the prototype for a general external function. */ +#if defined (__STDC__) || defined (WINDOWSNT) +#define P_(proto) proto +#else +#define P_(proto) () +#endif +@end example -@node Source Language -@section Using Languages Other Than C +@node Conditional Compilation +@section Conditional Compilation -Using a language other than C 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 C++ compiler -in order to compile your program. Thus, it is better if you write in C. +When supporting configuration options already known when building your +program we prefer using @code{if (... )} over conditional compilation, +as in the former case the compiler is able to perform more extensive +checking of all possible code paths. -But there are three situations when there is no disadvantage in using -some other language: +For example, please write -@itemize @bullet -@item -It is okay to use another language if your program contains an -interpreter for that language. +@smallexample + if (HAS_FOO) + ... + else + ... +@end smallexample -For example, if your program links with GUILE, it is ok to write part of -the program in Scheme or another language supported by GUILE. +instead of: -@item -It is okay to use another language in a tool specifically intended for -use with that language. +@smallexample + #ifdef HAS_FOO + ... + #else + ... + #endif +@end smallexample -This is okay because the only people who want to build the tool will be -those who have installed the other language anyway. +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. -@item -If an application is of interest to a narrow community, then perhaps -it's not important if the application is inconvenient to install. -@end itemize +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. -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. +In the case of function-like macros like @code{REVERSIBLE_CC_MODE} in +GCC which cannot be simply used in @code{if( ...)} statements, there is +an easy workaround. Simply introduce another macro +@code{HAS_REVERSIBLE_CC_MODE} as in the following example: + +@smallexample + #ifdef REVERSIBLE_CC_MODE + #define HAS_REVERSIBLE_CC_MODE 1 + #else + #define HAS_REVERSIBLE_CC_MODE 0 + #endif +@end smallexample @node Program Behavior @chapter Program Behavior for All Programs -This @value{CHAPTER} describes how to write robust software. It also -describes general standards for error messages, the command line interface, -and how libraries should behave. +This @value{CHAPTER} 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 for command line interfaces -* Option Table:: Table of long options. +* 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 @end menu @node Semantics @section Writing Robust Programs +@cindex arbitrary limits on data Avoid arbitrary limits on the length or number of @emph{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. +@cindex @code{NUL} characters Utilities reading files should not drop NUL characters, or any other -nonprinting characters @emph{including those with codes above 0177}. The -only sensible exceptions would be utilities specifically intended for -interface to certain types of printers that can't handle those characters. - +nonprinting characters @emph{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. + +@cindex error messages Check every system call for an error return, unless you know you wish to ignore errors. Include the system error text (from @code{perror} or equivalent) in @emph{every} error message resulting from a failing @@ -395,6 +553,8 @@ 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. +@cindex @code{malloc} return value +@cindex memory allocation failure Check every call to @code{malloc} or @code{realloc} to see if it returned zero. Check @code{realloc} even if you are making the block smaller; in a system that rounds block sizes to a power of 2, @@ -416,6 +576,7 @@ 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. +@cindex command-line arguments, decoding Use @code{getopt_long} to decode arguments, unless the argument syntax makes this unreasonable. @@ -428,12 +589,21 @@ 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 @code{readdir} or some other high-level interface. -These will be supported compatibly by GNU. +These are supported compatibly by GNU. -By default, the GNU system will provide the signal handling functions of -@sc{BSD} and of @sc{POSIX}. So GNU software should be written to use -these. +@cindex signal handling +The preferred signal handling facilities are the BSD variant of +@code{signal}, and the @sc{posix} @code{sigaction} function; the +alternative USG @code{signal} interface is an inferior design. +Nowadays, using the @sc{posix} signal functions may be the easiest way +to make a program portable. If you use @code{signal}, then on GNU/Linux +systems running GNU libc version 1, you should include +@file{bsd/signal.h} instead of @file{signal.h}, so as to get BSD +behavior. It is up to you whether to support systems where +@code{signal} has only the USG behavior, or give up on them. + +@cindex impossible conditions 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 @@ -448,12 +618,28 @@ 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. +@cindex temporary files +@cindex @code{TMPDIR} environment variable If you make temporary files, check the @code{TMPDIR} environment variable; if that variable is defined, use the specified directory instead of @file{/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: + +@example +fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0600); +@end example + +@noindent +or by using the @code{mkstemps} function from libiberty. + +In bash, use @code{set -C} to avoid this problem. + @node Libraries @section Library Behavior +@cindex libraries Try to make library functions reentrant. If they need to do dynamic storage allocation, at least try to avoid any nonreentrancy aside from @@ -473,16 +659,18 @@ 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 @samp{_}. They should also contain -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. +should have names beginning with @samp{_}. The @samp{_} 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. @node Errors @section Formatting Error Messages +@cindex formatting error messages +@cindex error messages, formatting Error messages from compilers should look like this: @@ -490,6 +678,20 @@ Error messages from compilers should look like this: @var{source-file-name}:@var{lineno}: @var{message} @end example +@noindent +If you want to mention the column number, use this format: + +@example +@var{source-file-name}:@var{lineno}:@var{column}: @var{message} +@end example + +@noindent +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: @example @@ -506,6 +708,12 @@ when there is an appropriate source file, or like this: @noindent when there is no relevant source file. +If you want to mention the column number, use this format: + +@example +@var{program}:@var{source-file-name}:@var{lineno}:@var{column}: @var{message} +@end example + 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 @@ -522,8 +730,10 @@ usage messages, should start with a capital letter. But they should not end with a period. @node User Interfaces -@section Standards for Command Line Interfaces +@section Standards for Interfaces Generally +@cindex program name and its behavior +@cindex behavior, dependent on program's name 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. @@ -531,10 +741,13 @@ 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. +@cindex output device and program's behavior 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. +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 @@ -550,13 +763,42 @@ output device type. For example, we provide a @code{dir} program much like @code{ls} except that its default output format is always multi-column format. -It is a good idea to follow the @sc{POSIX} guidelines for the +@node Graphical Interfaces +@section Standards for Graphical Interfaces +@cindex graphical user interface + +@cindex gtk +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. + +@cindex corba +@cindex gnome +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. + +@node Command-Line Interfaces +@section Standards for Command Line Interfaces +@cindex command-line interface + +@findex getopt +It is a good idea to follow the @sc{posix} guidelines for the command-line options of a program. The easiest way to do this is to use @code{getopt} to parse them. Note that the GNU version of @code{getopt} will normally permit options anywhere among the arguments unless the -special argument @samp{--} is used. This is not what @sc{POSIX} +special argument @samp{--} is used. This is not what @sc{posix} specifies; it is a GNU extension. +@cindex long-named options 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 @@ -576,16 +818,20 @@ 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. +@cindex standard command-line options All programs should support two standard options: @samp{--version} and @samp{--help}. @table @code +@cindex @samp{--version} option @item --version -This option should direct the program to information about its name, +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. +@cindex canonical name of a program +@cindex program's canonical name 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: @@ -658,12 +904,33 @@ 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 (@pxref{Internationalization}). If the translation's +character set supports it, the @samp{(C)} should be replaced with the +copyright symbol, as follows: + +@ifinfo +(the official copyright symbol, which is the letter C in a circle); +@end ifinfo +@ifnotinfo +@copyright{} +@end ifnotinfo + +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. + + +@cindex @samp{--help} option @item --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. +@cindex address for bug reports +@cindex bug reports Near the end of the @samp{--help} option's output there should be a line that says where to mail bug reports. It should have this format: @@ -674,11 +941,13 @@ Report bugs to @var{mailing-address}. @node Option Table @section Table of Long Options +@cindex long option names +@cindex 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 @email{gnu@@gnu.org} a list of them, with their +please send @email{bug-standards@@gnu.org} a list of them, with their meanings, so we can update the table. @c Please leave newlines between items in this table; it's much easier @@ -738,6 +1007,9 @@ and @code{unexpand}. @item avoid-wraps @samp{-n} in @code{wdiff}. +@item background +For server programs, run in the background. + @item backward-search @samp{-B} in @code{ctags}. @@ -862,6 +1134,9 @@ Used in @code{tar} and @code{cpio}. @item dereference-args @samp{-D} in @code{du}. +@item device +Specify an I/O device (special file name). + @item diacritics @samp{-d} in @code{recode}. @@ -994,6 +1269,11 @@ Used in @code{makeinfo}. @item force-prefix @samp{-F} in @code{shar}. +@item foreground +For server programs, run in the foreground; +in other words, don't do anything special to run the server +in the background. + @item format Used in @code{ls}, @code{time}, and @code{ptx}. @@ -1039,6 +1319,9 @@ Used to ask for brief usage information. @item hide-control-chars @samp{-q} in @code{ls}. +@item html +In @code{makeinfo}, output HTML. + @item idle @samp{-u} in @code{who}. @@ -1099,6 +1382,10 @@ Used to ask for brief usage information. @item info @samp{-i}, @samp{-l}, and @samp{-m} in Finger. +@item init-file +In some programs, specify the name of the file to read as the user's +init file. + @item initial @samp{-i} in @code{expand}. @@ -1117,6 +1404,9 @@ Used to ask for brief usage information. @item intermix-type @samp{-p} in @code{shar}. +@item iso-8601 +Used in @code{date} + @item jobs @samp{-j} in Make. @@ -1352,6 +1642,10 @@ Used in GDB. @item only-time @samp{-F} in @code{gprof}. +@item options +@samp{-o} in @code{getopt}, @code{fdlist}, @code{fdmount}, +@code{fdmountd}, and @code{fdumount}. + @item output In various programs, specify the output file name. @@ -1436,6 +1730,9 @@ Used in @code{tar} and @code{cp}. @item prompt @samp{-p} in @code{ed}. +@item proxy +Specify an HTTP proxy. + @item query-user @samp{-X} in @code{shar}. @@ -1564,6 +1861,12 @@ Used in many programs to inhibit the usual output. @item size @samp{-s} in @code{ls}. +@item 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. + @item sort Used in @code{ls}. @@ -1662,6 +1965,9 @@ Used in GDB and @code{objdump}. @item time Used in @code{ls} and @code{touch}. +@item timeout +Specify how long to wait before giving up on some operation. + @item to-stdout @samp{-O} in @code{tar}. @@ -1754,8 +2060,9 @@ Print the version number. @node Memory Usage @section Memory Usage +@cindex memory usage -If it typically uses just a few meg of memory, don't bother making any +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. @@ -1771,6 +2078,23 @@ 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 @code{malloc} returns zero. +@node File Usage +@section File Usage +@cindex file usage + +Programs should be prepared to operate when @file{/usr} and @file{/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 +@file{/usr} or @file{/etc}. + +There are two exceptions. @file{/etc} is used to store system +configuration information; it is reasonable for a program to modify +files in @file{/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. + @node Writing C @chapter Making The Best Use of C @@ -1781,7 +2105,7 @@ when writing GNU software. * Formatting:: Formatting Your Source Code * Comments:: Commenting Your Work * Syntactic Conventions:: Clean Use of C Constructs -* Names:: Naming Variables and Functions +* 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 @@ -1791,7 +2115,10 @@ when writing GNU software. @node Formatting @section Formatting Your Source Code +@cindex formatting source code +@cindex open brace +@cindex braces, in C source 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 @@ -1813,7 +2140,8 @@ concat (s1, s2) /* Name starts in column zero here */ @end example @noindent -or, if you want to use @sc{ansi} C, format the definition like this: +or, if you want to use Standard C syntax, format the definition like +this: @example static char * @@ -1823,7 +2151,7 @@ concat (char *s1, char *s2) @} @end example -In @sc{ansi} C, if the arguments don't fit nicely on one line, +In Standard C, if the arguments don't fit nicely on one line, split it like this: @example @@ -1833,7 +2161,25 @@ lots_of_args (int an_integer, long a_long, short a_short, @dots{} @end example -For the body of the function, we prefer code formatted like this: +The rest of this section gives our recommendations for other aspects of +C formatting style, which is also the default style of the @code{indent} +program in version 1.2 and newer. It corresponds to the options + +@smallexample +-nbad -bap -nbc -bbo -bl -bli2 -bls -ncdb -nce -cp1 -cs -di2 +-ndj -nfc1 -nfca -hnl -i2 -ip5 -lp -pcs -psl -nsc -nsob +@end smallexample + +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: @example if (x < foo (y, z)) @@ -1849,12 +2195,14 @@ else @} @end example +@cindex spaces before open-paren 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: +@cindex expressions, splitting @example if (foo_this_is_long && bar > win (x, y, z) && remaining_condition) @@ -1879,14 +2227,15 @@ mode = ((inmode[j] == VOIDmode Insert extra parentheses so that Emacs will indent the code properly. For example, the following indentation looks nice if you do it by hand, -but Emacs would mess it up: @example 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; @end example -But adding a set of parentheses solves the problem: +@noindent +but Emacs would alter it. Adding a set of parentheses produces +something that looks equally nice, and which Emacs will preserve: @example v = (rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000 @@ -1903,14 +2252,16 @@ do while (a > 0); @end example +@cindex formfeed +@cindex control-L 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. - @node Comments @section Commenting Your Work +@cindex commenting Every program should start with a comment saying briefly what it is for. Example: @samp{fmt - filter for simple filling of text}. @@ -1962,6 +2313,8 @@ There should be a comment on each static variable as well, like this: int truncate_lines; @end example +@cindex conditionals, comments for +@cindex @code{#endif}, commenting Every @samp{#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, @emph{including @@ -2003,9 +2356,23 @@ but, by contrast, write the comments this way for a @samp{#ifndef}: @node Syntactic Conventions @section Clean Use of C Constructs - -Please explicitly declare all arguments to functions. -Don't omit them just because they are @code{int}s. +@cindex syntactic conventions + +@cindex implicit @code{int} +@cindex function argument, declaring +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 @code{int} rather than omitting the +@code{int}. + +@cindex compiler warnings +@cindex @samp{-Wall} compiler option +Some programmers like to use the GCC @samp{-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 @samp{-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 @@ -2013,6 +2380,7 @@ source file should all go in one place near the beginning of the file should go in a header file. Don't put @code{extern} declarations inside functions. +@cindex temporary variables It used to be common practice to use the same local variables (with names like @code{tem}) over and over for different values within one function. Instead of doing this, it is better declare a separate local @@ -2024,6 +2392,7 @@ all its uses. This makes the program even cleaner. Don't use local variables or parameters that shadow global identifiers. +@cindex multiple variables in a line Don't declare multiple variables in one declaration that spans lines. Start a new declaration on each line, instead. For example, instead of this: @@ -2124,13 +2493,15 @@ if (foo == 0) fatal ("virtual memory exhausted"); @end example +@pindex lint Don't make the program ugly to placate @code{lint}. Please don't insert any casts to @code{void}. Zero without a cast is perfectly fine as a null pointer constant, except when calling a varargs function. -@node Names -@section Naming Variables and Functions +@node Names +@section Naming Variables, Functions, and Files +@cindex names of 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 @@ -2140,6 +2511,10 @@ 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 @code{enum} constants, and for name-prefixes @@ -2164,30 +2539,41 @@ When you want to define names with constant integer values, use @code{enum} rather than @samp{#define}. GDB knows about enumeration constants. -Use file names of 14 characters or less, to avoid creating gratuitous -problems on older System V systems. You can use the program -@code{doschk} to test for this. @code{doschk} also tests for potential -name conflicts if the files were loaded onto an MS-DOS file -system---something you may or may not care about. +@cindex file-name limitations +@pindex doschk +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 @code{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. @code{doschk} also reports file names longer than 14 +characters. @node System Portability @section Portability between System Types +@cindex 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 @sc{cpu}. The -amount and kinds of variation among GNU systems on different @sc{cpu}s -will be comparable to the variation among Linux-based GNU systems or -among BSD systems today. So the kinds of portability that are absolutely -necessary are quite limited. - -But many users do run GNU software on non-GNU Unix or Unix-like systems. -So supporting a variety of Unix-like systems is desirable, although not -paramount. - +compiled with the GNU C compiler, on various types of @sc{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. + +@pindex autoconf 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 @@ -2197,19 +2583,30 @@ written. Avoid using the format of semi-internal data bases (e.g., directories) when there is a higher-level alternative (@code{readdir}). +@cindex non-@sc{posix} systems, and portability As for systems that are not like Unix, such as MSDOS, Windows, the -Macintosh, VMS, and MVS, supporting them is usually so much work that it -is better if you don't. - -The planned GNU kernel is not finished yet, but you can tell which -facilities it will provide by looking at the GNU C Library Manual. The -GNU kernel is based on Mach, so the features of Mach will also be -available. However, if you use Mach features, you'll probably have -trouble debugging your program today. +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'' +@code{_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 @emph{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. @node CPU Portability @section Portability between @sc{cpu}s +@cindex data types, and portability +@cindex portability, and data types Even GNU systems will differ because of differences among @sc{cpu} types---for example, difference in byte ordering and alignment requirements. It is absolutely essential to handle these differences. @@ -2217,6 +2614,25 @@ However, don't make any effort to cater to the possibility that an @code{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 +@code{long} will be smaller than predefined types like @code{size_t}. +For example, the following code is ok: + +@example +printf ("size = %lu\n", (unsigned long) sizeof array); +printf ("diff = %ld\n", (long) (pointer2 - pointer1)); +@end example + +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 @code{off_t} are an exception: they are +longer than @code{long} on many platforms, so code like the above won't +work with them. One way to print an @code{off_t} value portably is to +print its digits yourself, one by one. + Don't assume that the address of an @code{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: @@ -2231,9 +2647,9 @@ while ((c = getchar()) != EOF) 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 @sc{ansi} C, so you can use -prototypes (conditionalized to be active only in @sc{ansi} C) to make -the code work on those systems. +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 @@ -2243,7 +2659,7 @@ that pass their arguments along to @code{printf} and friends: @example error (s, a1, a2, a3) char *s; - int a1, a2, a3; + char *a1, *a2, *a3; @{ fprintf (stderr, "error: "); fprintf (stderr, s, a1, a2, a3); @@ -2251,36 +2667,50 @@ error (s, a1, a2, a3) @end example @noindent -In practice, this works on all machines, and it is much simpler than any -``correct'' alternative. Be sure @emph{not} to use a prototype -for such functions. +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 @emph{not} to use a prototype for such +functions. -However, avoid casting pointers to integers unless you really need to. -These assumptions really 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---it is ok to do so, but you'll have to -make explicit provisions to handle different word sizes. +If you have decided to use Standard C, then you can instead define +@code{error} using @file{stdarg.h}, and pass the arguments along to +@code{vfprintf}. + +@cindex casting pointers to integers +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 @code{malloc} starts far away +from zero. @node System Functions @section Calling System Functions +@cindex library functions, and portability +@cindex portability, and library functions -C implementations differ substantially. @sc{ansi} C reduces but does not -eliminate the incompatibilities; meanwhile, many users wish to compile -GNU software with pre-@sc{ansi} compilers. This chapter gives -recommendations for how to use the more or less standard C library -functions to avoid unnecessary loss of portability. +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. @itemize @bullet @item -Don't use the value of @code{sprintf}. It returns the number of +Don't use the return value of @code{sprintf}. It returns the number of characters written on some systems, but not on all systems. @item +Be aware that @code{vfprintf} is not always available. + +@item @code{main} should be declared to return type @code{int}. It should terminate either by calling @code{exit} or by returning the integer status code; make sure it cannot ever return an undefined value. +@cindex declaration for system functions @item Don't declare system functions explicitly. @@ -2297,7 +2727,7 @@ actual conflicts. @item If you must declare a system function, don't specify the argument types. -Use an old-style declaration, not an @sc{ansi} prototype. The more you +Use an old-style declaration, not a Standard C prototype. The more you specify about the function, the more likely a conflict. @item @@ -2319,6 +2749,7 @@ exceptional systems (mostly 64-bit machines), you can use @code{realloc}---or put these declarations in configuration files specific to those systems. +@cindex string library functions @item The string functions require special treatment. Some Unix systems have a header file @file{string.h}; others have @file{strings.h}. Neither @@ -2329,7 +2760,7 @@ 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 @sc{ansi} +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: @@ -2359,7 +2790,7 @@ 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 @code{strchr} and -@code{strrchr} for new programs, since those are the standard @sc{ansi} +@code{strrchr} for new programs, since those are the standard names.) Declare both of those names as functions returning @code{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 @@ -2385,7 +2816,9 @@ One way to get them properly defined is to use Autoconf. @node Internationalization @section Internationalization +@cindex internationalization +@pindex gettext 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 @@ -2412,6 +2845,7 @@ 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, @samp{fileutils} for the GNU file utilities. +@cindex message text, and internationalization 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 @@ -2483,6 +2917,7 @@ printf (f->tried_implicit @node Mmap @section Mmap +@findex mmap Don't assume that @code{mmap} either works on all files or fails for all files. It may work on some files and fail on others. @@ -2499,10 +2934,20 @@ all these kinds of files. @node Documentation @chapter Documenting Programs +@cindex documentation + +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. @@ -2513,10 +2958,18 @@ all these kinds of files. @node GNU Manuals @section GNU Manuals -The preferred way to document part of the GNU system is to write a -manual in the Texinfo formatting language. See the Texinfo manual, -either the hardcopy, or the on-line version available through -@code{info} or the Emacs Info subsystem (@kbd{C-h i}). +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 @code{info} or the +Emacs Info subsystem (@kbd{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 @@ -2545,9 +2998,9 @@ have one manual for ``comparison of files'' which covers both of those programs, as well as @code{cmp}. By documenting these programs together, we can make the whole subject clearer. -The manual which discusses a program should 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 +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. @@ -2557,6 +3010,8 @@ 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 @@ -2570,22 +3025,62 @@ 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 +@ref{Index Entries, , Making Index Entries, texinfo, The GNU Texinfo +Manual}, and see @ref{Indexing Commands, , Defining the Entries of an +Index, texinfo, The GNU Texinfo manual}. + 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 -exceptions.) Also Unix man pages use a particular format which is +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 @emph{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 file names. +``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 violations of law. +``illegal'' for activities punishable by law. + +@node Doc Strings and Manuals +@section 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. @node Manual Structure Details @section Manual Structure Details +@cindex manual structure 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 @@ -2593,7 +3088,7 @@ 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 should have a node named +Each program documented in the manual should have a node named @samp{@var{program} Invocation} or @samp{Invoking @var{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 @@ -2605,14 +3100,57 @@ 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. -There will be automatic features for specifying a program name and -quickly reading just this part of its manual. +The @samp{--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. +each program described in the manual. + +@node License for Manuals +@section License for Manuals +@cindex 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 @uref{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. + +@node Manual Credits +@section Manual Credits +@cindex credits for manuals + +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. + +@node Printed Manuals +@section 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 +@url{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. @node NEWS File @section The NEWS File +@cindex @file{NEWS} file In addition to its manual, the package should have a file named @file{NEWS} which contains a list of user-visible changes worth @@ -2627,6 +3165,7 @@ user to that file. @node Change Logs @section Change Logs +@cindex 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 @@ -2641,6 +3180,7 @@ history of how the conflicting concepts arose and who they came from. * Style of Change Logs:: * Simple Changes:: * Conditional Changes:: +* Indicating the Part Changed:: @end menu @node Change Log Concepts @@ -2659,7 +3199,8 @@ 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 @file{ChangeLog} file. +to a @file{ChangeLog} file using @code{rcs2log}; in Emacs, the command +@kbd{C-x v a} (@code{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 @@ -2680,10 +3221,16 @@ Then describe the changes you made to that function or variable. @node Style of Change Logs @subsection Style of Change Logs +@cindex change logs, style -Here are some examples of change log entries: +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.) @example +1998-08-17 Richard Stallman <rms@@gnu.org> + * register.el (insert-register): Return nil. (jump-to-register): Likewise. @@ -2714,6 +3261,15 @@ 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 +@samp{)}, rather than @samp{,}, and opening the continuation with +@samp{(} as in this example: + +@example +* keyboard.c (menu_bar_items, tool_bar_items) +(Fexecute_extended_command): Deal with `keymap' property. +@end example + @node Simple Changes @subsection Simple Changes @@ -2721,9 +3277,10 @@ 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, 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.'' +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: @example * keyboard.c (Fcommand_execute): New arg SPECIAL. @@ -2743,6 +3300,8 @@ documentation says with the way the program actually works. @node Conditional Changes @subsection Conditional Changes +@cindex conditional changes, and change logs +@cindex change logs, conditional changes C programs often contain compile-time @code{#if} conditionals. Many changes are conditional; sometimes you add a new definition which is @@ -2782,8 +3341,23 @@ a certain macro is @emph{not} defined: (gethostname) [!HAVE_SOCKETS]: Replace with winsock version. @end example +@node Indicating the Part Changed +@subsection 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 @code{sh-while-getopts} that +deals with @code{sh} commands: + +@example +* progmodes/sh-script.el (sh-while-getopts) <sh>: Handle case that +user-specified option string is empty. +@end example + + @node Man Pages @section Man Pages +@cindex 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. @@ -2830,6 +3404,7 @@ with the FSF about the individual case. @node Managing Releases @chapter The Release Process +@cindex releasing 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 @@ -2841,13 +3416,15 @@ all GNU software. @menu * Configuration:: How Configuration Should Work -* Makefile Conventions:: Makefile Conventions +* Makefile Conventions:: Makefile Conventions * Releases:: Making Releases @end menu @node Configuration @section How Configuration Should Work +@cindex program configuration +@pindex configure Each GNU distribution should come with a shell script named @code{configure}. This script is given arguments which describe the kind of machine and system you want to compile the program for. @@ -2915,13 +3492,14 @@ The @code{configure} script needs to be able to decode all plausible alternatives for how to describe a machine. Thus, @samp{sun3-sunos4.1} would be a valid alias. For many programs, @samp{vax-dec-ultrix} would be an alias for @samp{vax-dec-bsd}, simply because the differences -between Ultrix and @sc{BSD} are rarely noticeable, but a few programs +between Ultrix and @sc{bsd} are rarely noticeable, but a few programs might need to distinguish them. @c Real 4.4BSD now runs on some Suns. There is a shell script called @file{config.sub} that you can use as a subroutine to validate system types and canonicalize aliases. +@cindex optional features, configure-time 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: @@ -2947,27 +3525,16 @@ to work with @var{package}. @c Giving an optional @var{parameter} of @c @samp{no} should omit @var{package}, if it is used by default. -Possible values of @var{package} include +Possible values of @var{package} include @samp{gnu-as} (or @samp{gas}), @samp{gnu-ld}, @samp{gnu-libc}, @samp{gdb}, -@samp{x}, +@samp{x}, and @samp{x-toolkit}. Do not use a @samp{--with} option to specify the file name to use to find certain files. That is outside the scope of what @samp{--with} options are for. - -@item --nfp -The target machine has no floating point processor. - -@item --gas -The target machine assembler is GAS, the GNU assembler. -This is obsolete; users should use @samp{--with-gnu-as} instead. - -@item --x -The target machine has the X Window System installed. -This is obsolete; users should use @samp{--with-x} instead. @end table All @code{configure} scripts should accept all of these ``detail'' @@ -2983,27 +3550,36 @@ 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 @code{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. +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 way to build a cross-compiler, cross-assembler, or what have you, is -to specify the option @samp{--host=@var{hosttype}} when running -@code{configure}. This specifies the host system without changing the -type of target system. The syntax for @var{hosttype} is the same as -described above. +The @code{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. -Bootstrapping a cross-compiler requires compiling it on a machine other -than the host it will run on. Compilation packages accept a -configuration option @samp{--build=@var{hosttype}} for specifying the -configuration on which you will compile them, in case that is different -from the host. +To configure a cross-compiler, cross-assembler, or what have you, you +should specify a target different from the host, using the configure +option @samp{--target=@var{targettype}}. The syntax for +@var{targettype} is the same as for the host type. So the command would +look like this: + +@example +./configure @var{hosttype} --target=@var{targettype} +@end example Programs for which cross-operation is not meaningful need not accept the -@samp{--host} option, because configuring an entire operating system for -cross-operation is not a meaningful thing. +@samp{--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 @samp{--build=@var{buildtype}} for specifying the +configuration on which you will compile them, but the configure script +should normally guess the build machine type (using +@file{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 @code{configure} script can simply @@ -3018,6 +3594,7 @@ ignore most of its arguments. @node Releases @section Making Releases +@cindex packaging Package the distribution of @code{Foo version 69.96} up in a gzipped tar file with the name @file{foo-69.96.tar.gz}. It should unpack into a @@ -3030,6 +3607,22 @@ files} and @dfn{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. +@cindex @file{README} file +The distribution should contain a file named @file{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 @file{README} file +should either state the version number of the package, or refer to where +in the package it can be found. + +The @file{README} file should refer to the file @file{INSTALL}, which +should contain an explanation of the installation procedure. + +The @file{README} file should also refer to the file which contains the +copying conditions. The GNU GPL, if used, should be in a file called +@file{COPYING}. If the GNU LGPL is used, it should be in a file called +@file{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 @@ -3054,7 +3647,7 @@ 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 +that some systems adhere to a foolish interpretation of the @sc{posix} standard, and refuse to open a longer name, rather than truncating as they did in the past. @@ -3073,6 +3666,7 @@ characters both before and after the period. Thus, are truncated to @file{foobarha.c} and @file{foobarha.o}, which are distinct. +@cindex @file{texinfo.tex}, in a distribution Include in your distribution a copy of the @file{texinfo.tex} you used to test print any @file{*.texinfo} or @file{*.texi} files. @@ -3082,12 +3676,67 @@ 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. +@node References +@chapter References to Non-Free Software and Documentation +@cindex references to non-free material + +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. + +@node Copying This Manual +@appendix Copying This Manual + +@menu +* GNU Free Documentation License:: License for copying this manual +@end menu + +@include fdl.texi + +@node Index +@unnumbered Index +@printindex cp + @contents @bye -Local variables: -update-date-leading-regexp: "@c This date is automagically updated when you save this file:\n@set lastupdate " -update-date-trailing-regexp: "" -eval: (load "/gd/gnuorg/update-date.el") -eval: (add-hook 'write-file-hooks 'update-date) -End: +@c Local variables: +@c eval: (add-hook 'write-file-hooks 'time-stamp) +@c time-stamp-start: "@set lastupdate " +@c time-stamp-end: "$" +@c time-stamp-format: "%:b %:d, %:y" +@c compile-command: "make just-standards" +@c End: |