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diff --git a/standards.info b/standards.info new file mode 100644 index 0000000..1b111f9 --- /dev/null +++ b/standards.info @@ -0,0 +1,3837 @@ +This is Info file standards.info, produced by Makeinfo version 1.67 +from the input file /home/bje/autoconf-2.13/standards.texi. + +START-INFO-DIR-ENTRY +* Standards: (standards). GNU coding standards. +END-INFO-DIR-ENTRY + + GNU Coding Standards Copyright (C) 1992, 1993, 1994, 1995, 1996, +1997, 1998 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. + + +File: standards.info, Node: Top, Next: Preface, Prev: (dir), Up: (dir) + +Version +******* + + Last updated August 26, 1998. + +* Menu: + +* Preface:: About the GNU Coding Standards +* Intellectual Property:: 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 + + +File: standards.info, Node: Preface, Next: Intellectual Property, Prev: Top, Up: Top + +About the GNU Coding Standards +****************************** + + The GNU Coding Standards were written by Richard Stallman and other +GNU Project volunteers. Their purpose is to make the GNU system clean, +consistent, and easy to install. This document can also be read as a +guide to writing portable, robust and reliable programs. It focuses on +programs written in C, but many of the rules and principles are useful +even if you write in another programming language. The rules often +state reasons for writing in a certain way. + + Corrections or suggestions for this document should be sent to +<gnu@gnu.org>. If you make a suggestion, please include a suggested +new wording for it; our time is limited. We prefer a context diff to +the `standards.texi' or `make-stds.texi' files, but if you don't have +those files, please mail your suggestion anyway. + + This release of the GNU Coding Standards was last updated August 26, +1998. + + +File: standards.info, Node: Intellectual Property, Next: Design Advice, Prev: Preface, Up: Top + +Keeping Free Software Free +************************** + + This node discusses how you can make sure that GNU software remains +unencumbered. + +* Menu: + +* Reading Non-Free Code:: Referring to Proprietary Programs +* Contributions:: Accepting Contributions + + +File: standards.info, Node: Reading Non-Free Code, Next: Contributions, Up: Intellectual Property + +Referring to Proprietary Programs +================================= + + Don't in any circumstances refer to Unix source code for or during +your work on GNU! (Or to any other proprietary programs.) + + If you have a vague recollection of the internals of a Unix program, +this does not absolutely mean you can't write an imitation of it, but +do try to organize the imitation internally along different lines, +because this is likely to make the details of the Unix version +irrelevant and dissimilar to your results. + + For example, Unix utilities were generally optimized to minimize +memory use; if you go for speed instead, your program will be very +different. You could keep the entire input file in core and scan it +there instead of using stdio. Use a smarter algorithm discovered more +recently than the Unix program. Eliminate use of temporary files. Do +it in one pass instead of two (we did this in the assembler). + + Or, on the contrary, emphasize simplicity instead of speed. For some +applications, the speed of today's computers makes simpler algorithms +adequate. + + Or go for generality. For example, Unix programs often have static +tables or fixed-size strings, which make for arbitrary limits; use +dynamic allocation instead. Make sure your program handles NULs and +other funny characters in the input files. Add a programming language +for extensibility and write part of the program in that language. + + Or turn some parts of the program into independently usable +libraries. Or use a simple garbage collector instead of tracking +precisely when to free memory, or use a new GNU facility such as +obstacks. + + +File: standards.info, Node: Contributions, Prev: Reading Non-Free Code, Up: Intellectual Property + +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. *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 enough. + + So, before adding in any contributions from other people, please tell +us, so we can arrange to get the papers. Then wait until we tell you +that we have received the signed papers, before you actually use the +contribution. + + This applies both before you release the program and afterward. If +you receive diffs to fix a bug, and they make significant changes, we +need legal papers for that change. + + This also applies to comments and documentation files. For copyright +law, comments and code are just text. Copyright applies to all kinds of +text, so we need legal papers for all kinds. + + 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! + + The very worst thing is if you forget to tell us about the other +contributor. We could be very embarrassed in court some day as a +result. + + We have more detailed advice for maintainers of programs; if you have +reached the stage of actually maintaining a program for GNU (whether +released or not), please ask us for a copy. + + +File: standards.info, Node: Design Advice, Next: Program Behavior, Prev: Intellectual Property, Up: Top + +General Program Design +********************** + + This node discusses some of the issues you should take into account +when designing your program. + +* Menu: + +* Compatibility:: Compatibility with other implementations +* Using Extensions:: Using non-standard features +* ANSI C:: Using ANSI C features +* Source Language:: Using languages other than C + + +File: standards.info, Node: Compatibility, Next: Using Extensions, Up: Design Advice + +Compatibility with Other Implementations +======================================== + + With occasional exceptions, utility programs and libraries for GNU +should be upward compatible with those in Berkeley Unix, and upward +compatible with ANSI C if ANSI C specifies their behavior, and upward +compatible with POSIX if POSIX specifies their behavior. + + When these standards conflict, it is useful to offer compatibility +modes for each of them. + + ANSI C and POSIX prohibit many kinds of extensions. Feel free to +make the extensions anyway, and include a `--ansi', `--posix', or +`--compatible' option to turn them off. However, if the extension has +a significant chance of breaking any real programs or scripts, then it +is not really upward compatible. Try to redesign its interface. + + Many GNU programs suppress extensions that conflict with POSIX if the +environment variable `POSIXLY_CORRECT' is defined (even if it is +defined with a null value). Please make your program recognize this +variable if appropriate. + + When a feature is used only by users (not by programs or command +files), and it is done poorly in Unix, feel free to replace it +completely with something totally different and better. (For example, +`vi' is replaced with Emacs.) But it is nice to offer a compatible +feature as well. (There is a free `vi' clone, so we offer it.) + + Additional useful features not in Berkeley Unix are welcome. + + +File: standards.info, Node: Using Extensions, Next: ANSI C, Prev: Compatibility, Up: Design Advice + +Using Non-standard Features +=========================== + + Many GNU facilities that already exist support a number of convenient +extensions over the comparable Unix facilities. Whether to use these +extensions in implementing your program is a difficult question. + + On the one hand, using the extensions can make a cleaner program. +On the other hand, people will not be able to build the program unless +the other GNU tools are available. This might cause the program to +work on fewer kinds of machines. + + With some extensions, it might be easy to provide both alternatives. +For example, you can define functions with a "keyword" `INLINE' and +define that as a macro to expand into either `inline' or nothing, +depending on the compiler. + + In general, perhaps it is best not to use the extensions if you can +straightforwardly do without them, but to use the extensions if they +are a big improvement. + + An exception to this rule are the large, established programs (such +as Emacs) which run on a great variety of systems. Such programs would +be broken by use of GNU extensions. + + 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. + + +File: standards.info, Node: ANSI C, Next: Source Language, Prev: Using Extensions, Up: Design Advice + +ANSI C and pre-ANSI C +===================== + + Do not ever use the "trigraph" feature of ANSI C. + + ANSI C is widespread enough now that it is ok to write new programs +that use ANSI C features (and therefore will not work in non-ANSI +compilers). And if a program is already written in ANSI C, there's no +need to convert it to support non-ANSI compilers. + + However, it is easy to support non-ANSI compilers in most programs, +so you might still consider doing so when you write a program. Instead +of writing function definitions in ANSI prototype form, + + int + foo (int x, int y) + ... + +write the definition in pre-ANSI style like this, + + int + foo (x, y) + int x, y; + ... + +and use a separate declaration to specify the argument prototype: + + int foo (int, int); + + You need such a declaration anyway, in a header file, to get the +benefit of 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-ANSI style. + + If you don't know non-ANSI C, there's no need to learn it; just +write in ANSI C. + + +File: standards.info, Node: Source Language, Prev: ANSI C, Up: Design Advice + +Using Languages Other Than C +============================ + + 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. + + But there are three situations when there is no disadvantage in using +some other language: + + * It is okay to use another language if your program contains an + interpreter for that language. + + 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. + + * It is okay to use another language in a tool specifically intended + for use with that language. + + This is okay because the only people who want to build the tool + will be those who have installed the other language anyway. + + * If an application is of interest to a narrow community, then + perhaps it's not important if the application is inconvenient to + install. + + 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. + + +File: standards.info, Node: Program Behavior, Next: Writing C, Prev: Design Advice, Up: Top + +Program Behavior for All Programs +********************************* + + This node describes how to write 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. +* Memory Usage:: When and how to care about memory needs + + +File: standards.info, Node: Semantics, Next: Libraries, Up: Program Behavior + +Writing Robust Programs +======================= + + Avoid arbitrary limits on the length or number of *any* data +structure, including file names, lines, files, and symbols, by +allocating all data structures dynamically. In most Unix utilities, +"long lines are silently truncated". This is not acceptable in a GNU +utility. + + Utilities reading files should not drop NUL characters, or any other +nonprinting characters *including those with codes above 0177*. The +only sensible exceptions would be utilities specifically intended for +interface to certain types of printers that can't handle those +characters. + + Check every system call for an error return, unless you know you +wish to ignore errors. Include the system error text (from `perror' or +equivalent) in *every* error message resulting from a failing system +call, as well as the name of the file if any and the name of the +utility. Just "cannot open foo.c" or "stat failed" is not sufficient. + + Check every call to `malloc' or `realloc' to see if it returned +zero. Check `realloc' even if you are making the block smaller; in a +system that rounds block sizes to a power of 2, `realloc' may get a +different block if you ask for less space. + + In Unix, `realloc' can destroy the storage block if it returns zero. +GNU `realloc' does not have this bug: if it fails, the original block +is unchanged. Feel free to assume the bug is fixed. If you wish to +run your program on Unix, and wish to avoid lossage in this case, you +can use the GNU `malloc'. + + You must expect `free' to alter the contents of the block that was +freed. Anything you want to fetch from the block, you must fetch before +calling `free'. + + If `malloc' fails in a noninteractive program, make that a fatal +error. In an interactive program (one that reads commands from the +user), it is better to abort the command and return to the command +reader loop. This allows the user to kill other processes to free up +virtual memory, and then try the command again. + + Use `getopt_long' to decode arguments, unless the argument syntax +makes this unreasonable. + + When static storage is to be written in during program execution, use +explicit C code to initialize it. Reserve C initialized declarations +for data that will not be changed. + + Try to avoid low-level interfaces to obscure Unix data structures +(such as file directories, utmp, or the layout of kernel memory), since +these are less likely to work compatibly. If you need to find all the +files in a directory, use `readdir' or some other high-level interface. +These will be supported compatibly by GNU. + + The preferred signal handling facilities are the BSD variant of +`signal', and the POSIX `sigaction' function; the alternative USG +`signal' interface is an inferior design. + + Nowadays, using the POSIX signal functions may be the easiest way to +make a program portable. If you use `signal', then on GNU/Linux +systems running GNU libc version 1, you should include `bsd/signal.h' +instead of `signal.h', so as to get BSD behavior. It is up to you +whether to support systems where `signal' has only the USG behavior, or +give up on them. + + In error checks that detect "impossible" conditions, just abort. +There is usually no point in printing any message. These checks +indicate the existence of bugs. Whoever wants to fix the bugs will have +to read the source code and run a debugger. So explain the problem with +comments in the source. The relevant data will be in variables, which +are easy to examine with the debugger, so there is no point moving them +elsewhere. + + Do not use a count of errors as the exit status for a program. +*That does not work*, because exit status values are limited to 8 bits +(0 through 255). A single run of the program might have 256 errors; if +you try to return 256 as the exit status, the parent process will see 0 +as the status, and it will appear that the program succeeded. + + If you make temporary files, check the `TMPDIR' environment +variable; if that variable is defined, use the specified directory +instead of `/tmp'. + + +File: standards.info, Node: Libraries, Next: Errors, Prev: Semantics, Up: Program Behavior + +Library Behavior +================ + + Try to make library functions reentrant. If they need to do dynamic +storage allocation, at least try to avoid any nonreentrancy aside from +that of `malloc' itself. + + Here are certain name conventions for libraries, to avoid name +conflicts. + + Choose a name prefix for the library, more than two characters long. +All external function and variable names should start with this prefix. +In addition, there should only be one of these in any given library +member. This usually means putting each one in a separate source file. + + An exception can be made when two external symbols are always used +together, so that no reasonable program could use one without the +other; then they can both go in the same file. + + External symbols that are not documented entry points for the user +should have names beginning with `_'. 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. + + Static functions and variables can be used as you like and need not +fit any naming convention. + + +File: standards.info, Node: Errors, Next: User Interfaces, Prev: Libraries, Up: Program Behavior + +Formatting Error Messages +========================= + + Error messages from compilers should look like this: + + SOURCE-FILE-NAME:LINENO: MESSAGE + + Error messages from other noninteractive programs should look like +this: + + PROGRAM:SOURCE-FILE-NAME:LINENO: MESSAGE + +when there is an appropriate source file, or like this: + + PROGRAM: MESSAGE + +when there is no relevant source file. + + In an interactive program (one that is reading commands from a +terminal), it is better not to include the program name in an error +message. The place to indicate which program is running is in the +prompt or with the screen layout. (When the same program runs with +input from a source other than a terminal, it is not interactive and +would do best to print error messages using the noninteractive style.) + + The string MESSAGE should not begin with a capital letter when it +follows a program name and/or file name. Also, it should not end with +a period. + + Error messages from interactive programs, and other messages such as +usage messages, should start with a capital letter. But they should not +end with a period. + + +File: standards.info, Node: User Interfaces, Next: Option Table, Prev: Errors, Up: Program Behavior + +Standards for Command Line Interfaces +===================================== + + Please don't make the behavior of a utility depend on the name used +to invoke it. It is useful sometimes to make a link to a utility with +a different name, and that should not change what it does. + + Instead, use a run time option or a compilation switch or both to +select among the alternate behaviors. + + Likewise, please don't make the behavior of the program depend on the +type of output device it is used with. Device independence is an +important principle of the system's design; do not compromise it merely +to save someone from typing an option now and then. (Variation in error +message syntax when using a terminal is ok, because that is a side issue +that people do not depend on.) + + If you think one behavior is most useful when the output is to a +terminal, and another is most useful when the output is a file or a +pipe, then it is usually best to make the default behavior the one that +is useful with output to a terminal, and have an option for the other +behavior. + + Compatibility requires certain programs to depend on the type of +output device. It would be disastrous if `ls' or `sh' did not do so in +the way all users expect. In some of these cases, we supplement the +program with a preferred alternate version that does not depend on the +output device type. For example, we provide a `dir' program much like +`ls' except that its default output format is always multi-column +format. + + It is a good idea to follow the POSIX guidelines for the +command-line options of a program. The easiest way to do this is to use +`getopt' to parse them. Note that the GNU version of `getopt' will +normally permit options anywhere among the arguments unless the special +argument `--' is used. This is not what POSIX specifies; it is a GNU +extension. + + Please define long-named options that are equivalent to the +single-letter Unix-style options. We hope to make GNU more user +friendly this way. This is easy to do with the GNU function +`getopt_long'. + + One of the advantages of long-named options is that they can be +consistent from program to program. For example, users should be able +to expect the "verbose" option of any GNU program which has one, to be +spelled precisely `--verbose'. To achieve this uniformity, look at the +table of common long-option names when you choose the option names for +your program (*note Option Table::.). + + It is usually a good idea for file names given as ordinary arguments +to be input files only; any output files would be specified using +options (preferably `-o' or `--output'). Even if you allow an output +file name as an ordinary argument for compatibility, try to provide an +option as another way to specify it. This will lead to more consistency +among GNU utilities, and fewer idiosyncracies for users to remember. + + All programs should support two standard options: `--version' and +`--help'. + +`--version' + This option should direct the program to information about its + name, version, origin and legal status, all on standard output, + and then exit successfully. Other options and arguments should be + ignored once this is seen, and the program should not perform its + normal function. + + The first line is meant to be easy for a program to parse; the + version number proper starts after the last space. In addition, + it contains the canonical name for this program, in this format: + + GNU Emacs 19.30 + + The program's name should be a constant string; *don't* compute it + from `argv[0]'. The idea is to state the standard or canonical + name for the program, not its file name. There are other ways to + find out the precise file name where a command is found in `PATH'. + + If the program is a subsidiary part of a larger package, mention + the package name in parentheses, like this: + + emacsserver (GNU Emacs) 19.30 + + If the package has a version number which is different from this + program's version number, you can mention the package version + number just before the close-parenthesis. + + If you *need* to mention the version numbers of libraries which + are distributed separately from the package which contains this + program, you can do so by printing an additional line of version + info for each library you want to mention. Use the same format + for these lines as for the first line. + + Please do not mention all of the libraries that the program uses + "just for completeness"--that would produce a lot of unhelpful + clutter. Please mention library version numbers only if you find + in practice that they are very important to you in debugging. + + The following line, after the version number line or lines, should + be a copyright notice. If more than one copyright notice is + called for, put each on a separate line. + + Next should follow a brief statement that the program is free + software, and that users are free to copy and change it on certain + conditions. If the program is covered by the GNU GPL, say so + here. Also mention that there is no warranty, to the extent + permitted by law. + + It is ok to finish the output with a list of the major authors of + the program, as a way of giving credit. + + Here's an example of output that follows these rules: + + GNU Emacs 19.34.5 + Copyright (C) 1996 Free Software Foundation, Inc. + GNU Emacs comes with NO WARRANTY, + to the extent permitted by law. + You may redistribute copies of GNU Emacs + under the terms of the GNU General Public License. + For more information about these matters, + see the files named COPYING. + + You should adapt this to your program, of course, filling in the + proper year, copyright holder, name of program, and the references + to distribution terms, and changing the rest of the wording as + necessary. + + This copyright notice only needs to mention the most recent year in + which changes were made--there's no need to list the years for + previous versions' changes. You don't have to mention the name of + the program in these notices, if that is inconvenient, since it + appeared in the first line. + +`--help' + This option should output brief documentation for how to invoke the + program, on standard output, then exit successfully. Other + options and arguments should be ignored once this is seen, and the + program should not perform its normal function. + + Near the end of the `--help' option's output there should be a line + that says where to mail bug reports. It should have this format: + + Report bugs to MAILING-ADDRESS. + + +File: standards.info, Node: Option Table, Next: Memory Usage, Prev: User Interfaces, Up: Program Behavior + +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 <gnu@gnu.org> a list of them, with their meanings, so we +can update the table. + +`after-date' + `-N' in `tar'. + +`all' + `-a' in `du', `ls', `nm', `stty', `uname', and `unexpand'. + +`all-text' + `-a' in `diff'. + +`almost-all' + `-A' in `ls'. + +`append' + `-a' in `etags', `tee', `time'; `-r' in `tar'. + +`archive' + `-a' in `cp'. + +`archive-name' + `-n' in `shar'. + +`arglength' + `-l' in `m4'. + +`ascii' + `-a' in `diff'. + +`assign' + `-v' in `gawk'. + +`assume-new' + `-W' in Make. + +`assume-old' + `-o' in Make. + +`auto-check' + `-a' in `recode'. + +`auto-pager' + `-a' in `wdiff'. + +`auto-reference' + `-A' in `ptx'. + +`avoid-wraps' + `-n' in `wdiff'. + +`background' + For server programs, run in the background. + +`backward-search' + `-B' in `ctags'. + +`basename' + `-f' in `shar'. + +`batch' + Used in GDB. + +`baud' + Used in GDB. + +`before' + `-b' in `tac'. + +`binary' + `-b' in `cpio' and `diff'. + +`bits-per-code' + `-b' in `shar'. + +`block-size' + Used in `cpio' and `tar'. + +`blocks' + `-b' in `head' and `tail'. + +`break-file' + `-b' in `ptx'. + +`brief' + Used in various programs to make output shorter. + +`bytes' + `-c' in `head', `split', and `tail'. + +`c++' + `-C' in `etags'. + +`catenate' + `-A' in `tar'. + +`cd' + Used in various programs to specify the directory to use. + +`changes' + `-c' in `chgrp' and `chown'. + +`classify' + `-F' in `ls'. + +`colons' + `-c' in `recode'. + +`command' + `-c' in `su'; `-x' in GDB. + +`compare' + `-d' in `tar'. + +`compat' + Used in `gawk'. + +`compress' + `-Z' in `tar' and `shar'. + +`concatenate' + `-A' in `tar'. + +`confirmation' + `-w' in `tar'. + +`context' + Used in `diff'. + +`copyleft' + `-W copyleft' in `gawk'. + +`copyright' + `-C' in `ptx', `recode', and `wdiff'; `-W copyright' in `gawk'. + +`core' + Used in GDB. + +`count' + `-q' in `who'. + +`count-links' + `-l' in `du'. + +`create' + Used in `tar' and `cpio'. + +`cut-mark' + `-c' in `shar'. + +`cxref' + `-x' in `ctags'. + +`date' + `-d' in `touch'. + +`debug' + `-d' in Make and `m4'; `-t' in Bison. + +`define' + `-D' in `m4'. + +`defines' + `-d' in Bison and `ctags'. + +`delete' + `-D' in `tar'. + +`dereference' + `-L' in `chgrp', `chown', `cpio', `du', `ls', and `tar'. + +`dereference-args' + `-D' in `du'. + +`diacritics' + `-d' in `recode'. + +`dictionary-order' + `-d' in `look'. + +`diff' + `-d' in `tar'. + +`digits' + `-n' in `csplit'. + +`directory' + Specify the directory to use, in various programs. In `ls', it + means to show directories themselves rather than their contents. + In `rm' and `ln', it means to not treat links to directories + specially. + +`discard-all' + `-x' in `strip'. + +`discard-locals' + `-X' in `strip'. + +`dry-run' + `-n' in Make. + +`ed' + `-e' in `diff'. + +`elide-empty-files' + `-z' in `csplit'. + +`end-delete' + `-x' in `wdiff'. + +`end-insert' + `-z' in `wdiff'. + +`entire-new-file' + `-N' in `diff'. + +`environment-overrides' + `-e' in Make. + +`eof' + `-e' in `xargs'. + +`epoch' + Used in GDB. + +`error-limit' + Used in `makeinfo'. + +`error-output' + `-o' in `m4'. + +`escape' + `-b' in `ls'. + +`exclude-from' + `-X' in `tar'. + +`exec' + Used in GDB. + +`exit' + `-x' in `xargs'. + +`exit-0' + `-e' in `unshar'. + +`expand-tabs' + `-t' in `diff'. + +`expression' + `-e' in `sed'. + +`extern-only' + `-g' in `nm'. + +`extract' + `-i' in `cpio'; `-x' in `tar'. + +`faces' + `-f' in `finger'. + +`fast' + `-f' in `su'. + +`fatal-warnings' + `-E' in `m4'. + +`file' + `-f' in `info', `gawk', Make, `mt', and `tar'; `-n' in `sed'; `-r' + in `touch'. + +`field-separator' + `-F' in `gawk'. + +`file-prefix' + `-b' in Bison. + +`file-type' + `-F' in `ls'. + +`files-from' + `-T' in `tar'. + +`fill-column' + Used in `makeinfo'. + +`flag-truncation' + `-F' in `ptx'. + +`fixed-output-files' + `-y' in Bison. + +`follow' + `-f' in `tail'. + +`footnote-style' + Used in `makeinfo'. + +`force' + `-f' in `cp', `ln', `mv', and `rm'. + +`force-prefix' + `-F' in `shar'. + +`foreground' + For server programs, run in the foreground; in other words, don't + do anything special to run the server in the background. + +`format' + Used in `ls', `time', and `ptx'. + +`freeze-state' + `-F' in `m4'. + +`fullname' + Used in GDB. + +`gap-size' + `-g' in `ptx'. + +`get' + `-x' in `tar'. + +`graphic' + `-i' in `ul'. + +`graphics' + `-g' in `recode'. + +`group' + `-g' in `install'. + +`gzip' + `-z' in `tar' and `shar'. + +`hashsize' + `-H' in `m4'. + +`header' + `-h' in `objdump' and `recode' + +`heading' + `-H' in `who'. + +`help' + Used to ask for brief usage information. + +`here-delimiter' + `-d' in `shar'. + +`hide-control-chars' + `-q' in `ls'. + +`idle' + `-u' in `who'. + +`ifdef' + `-D' in `diff'. + +`ignore' + `-I' in `ls'; `-x' in `recode'. + +`ignore-all-space' + `-w' in `diff'. + +`ignore-backups' + `-B' in `ls'. + +`ignore-blank-lines' + `-B' in `diff'. + +`ignore-case' + `-f' in `look' and `ptx'; `-i' in `diff' and `wdiff'. + +`ignore-errors' + `-i' in Make. + +`ignore-file' + `-i' in `ptx'. + +`ignore-indentation' + `-I' in `etags'. + +`ignore-init-file' + `-f' in Oleo. + +`ignore-interrupts' + `-i' in `tee'. + +`ignore-matching-lines' + `-I' in `diff'. + +`ignore-space-change' + `-b' in `diff'. + +`ignore-zeros' + `-i' in `tar'. + +`include' + `-i' in `etags'; `-I' in `m4'. + +`include-dir' + `-I' in Make. + +`incremental' + `-G' in `tar'. + +`info' + `-i', `-l', and `-m' in Finger. + +`initial' + `-i' in `expand'. + +`initial-tab' + `-T' in `diff'. + +`inode' + `-i' in `ls'. + +`interactive' + `-i' in `cp', `ln', `mv', `rm'; `-e' in `m4'; `-p' in `xargs'; + `-w' in `tar'. + +`intermix-type' + `-p' in `shar'. + +`jobs' + `-j' in Make. + +`just-print' + `-n' in Make. + +`keep-going' + `-k' in Make. + +`keep-files' + `-k' in `csplit'. + +`kilobytes' + `-k' in `du' and `ls'. + +`language' + `-l' in `etags'. + +`less-mode' + `-l' in `wdiff'. + +`level-for-gzip' + `-g' in `shar'. + +`line-bytes' + `-C' in `split'. + +`lines' + Used in `split', `head', and `tail'. + +`link' + `-l' in `cpio'. + +`lint' +`lint-old' + Used in `gawk'. + +`list' + `-t' in `cpio'; `-l' in `recode'. + +`list' + `-t' in `tar'. + +`literal' + `-N' in `ls'. + +`load-average' + `-l' in Make. + +`login' + Used in `su'. + +`machine' + No listing of which programs already use this; someone should + check to see if any actually do, and tell <gnu@gnu.org>. + +`macro-name' + `-M' in `ptx'. + +`mail' + `-m' in `hello' and `uname'. + +`make-directories' + `-d' in `cpio'. + +`makefile' + `-f' in Make. + +`mapped' + Used in GDB. + +`max-args' + `-n' in `xargs'. + +`max-chars' + `-n' in `xargs'. + +`max-lines' + `-l' in `xargs'. + +`max-load' + `-l' in Make. + +`max-procs' + `-P' in `xargs'. + +`mesg' + `-T' in `who'. + +`message' + `-T' in `who'. + +`minimal' + `-d' in `diff'. + +`mixed-uuencode' + `-M' in `shar'. + +`mode' + `-m' in `install', `mkdir', and `mkfifo'. + +`modification-time' + `-m' in `tar'. + +`multi-volume' + `-M' in `tar'. + +`name-prefix' + `-a' in Bison. + +`nesting-limit' + `-L' in `m4'. + +`net-headers' + `-a' in `shar'. + +`new-file' + `-W' in Make. + +`no-builtin-rules' + `-r' in Make. + +`no-character-count' + `-w' in `shar'. + +`no-check-existing' + `-x' in `shar'. + +`no-common' + `-3' in `wdiff'. + +`no-create' + `-c' in `touch'. + +`no-defines' + `-D' in `etags'. + +`no-deleted' + `-1' in `wdiff'. + +`no-dereference' + `-d' in `cp'. + +`no-inserted' + `-2' in `wdiff'. + +`no-keep-going' + `-S' in Make. + +`no-lines' + `-l' in Bison. + +`no-piping' + `-P' in `shar'. + +`no-prof' + `-e' in `gprof'. + +`no-regex' + `-R' in `etags'. + +`no-sort' + `-p' in `nm'. + +`no-split' + Used in `makeinfo'. + +`no-static' + `-a' in `gprof'. + +`no-time' + `-E' in `gprof'. + +`no-timestamp' + `-m' in `shar'. + +`no-validate' + Used in `makeinfo'. + +`no-wait' + Used in `emacsclient'. + +`no-warn' + Used in various programs to inhibit warnings. + +`node' + `-n' in `info'. + +`nodename' + `-n' in `uname'. + +`nonmatching' + `-f' in `cpio'. + +`nstuff' + `-n' in `objdump'. + +`null' + `-0' in `xargs'. + +`number' + `-n' in `cat'. + +`number-nonblank' + `-b' in `cat'. + +`numeric-sort' + `-n' in `nm'. + +`numeric-uid-gid' + `-n' in `cpio' and `ls'. + +`nx' + Used in GDB. + +`old-archive' + `-o' in `tar'. + +`old-file' + `-o' in Make. + +`one-file-system' + `-l' in `tar', `cp', and `du'. + +`only-file' + `-o' in `ptx'. + +`only-prof' + `-f' in `gprof'. + +`only-time' + `-F' in `gprof'. + +`output' + In various programs, specify the output file name. + +`output-prefix' + `-o' in `shar'. + +`override' + `-o' in `rm'. + +`overwrite' + `-c' in `unshar'. + +`owner' + `-o' in `install'. + +`paginate' + `-l' in `diff'. + +`paragraph-indent' + Used in `makeinfo'. + +`parents' + `-p' in `mkdir' and `rmdir'. + +`pass-all' + `-p' in `ul'. + +`pass-through' + `-p' in `cpio'. + +`port' + `-P' in `finger'. + +`portability' + `-c' in `cpio' and `tar'. + +`posix' + Used in `gawk'. + +`prefix-builtins' + `-P' in `m4'. + +`prefix' + `-f' in `csplit'. + +`preserve' + Used in `tar' and `cp'. + +`preserve-environment' + `-p' in `su'. + +`preserve-modification-time' + `-m' in `cpio'. + +`preserve-order' + `-s' in `tar'. + +`preserve-permissions' + `-p' in `tar'. + +`print' + `-l' in `diff'. + +`print-chars' + `-L' in `cmp'. + +`print-data-base' + `-p' in Make. + +`print-directory' + `-w' in Make. + +`print-file-name' + `-o' in `nm'. + +`print-symdefs' + `-s' in `nm'. + +`printer' + `-p' in `wdiff'. + +`prompt' + `-p' in `ed'. + +`query-user' + `-X' in `shar'. + +`question' + `-q' in Make. + +`quiet' + Used in many programs to inhibit the usual output. *Note:* every + program accepting `--quiet' should accept `--silent' as a synonym. + +`quiet-unshar' + `-Q' in `shar' + +`quote-name' + `-Q' in `ls'. + +`rcs' + `-n' in `diff'. + +`re-interval' + Used in `gawk'. + +`read-full-blocks' + `-B' in `tar'. + +`readnow' + Used in GDB. + +`recon' + `-n' in Make. + +`record-number' + `-R' in `tar'. + +`recursive' + Used in `chgrp', `chown', `cp', `ls', `diff', and `rm'. + +`reference-limit' + Used in `makeinfo'. + +`references' + `-r' in `ptx'. + +`regex' + `-r' in `tac' and `etags'. + +`release' + `-r' in `uname'. + +`reload-state' + `-R' in `m4'. + +`relocation' + `-r' in `objdump'. + +`rename' + `-r' in `cpio'. + +`replace' + `-i' in `xargs'. + +`report-identical-files' + `-s' in `diff'. + +`reset-access-time' + `-a' in `cpio'. + +`reverse' + `-r' in `ls' and `nm'. + +`reversed-ed' + `-f' in `diff'. + +`right-side-defs' + `-R' in `ptx'. + +`same-order' + `-s' in `tar'. + +`same-permissions' + `-p' in `tar'. + +`save' + `-g' in `stty'. + +`se' + Used in GDB. + +`sentence-regexp' + `-S' in `ptx'. + +`separate-dirs' + `-S' in `du'. + +`separator' + `-s' in `tac'. + +`sequence' + Used by `recode' to chose files or pipes for sequencing passes. + +`shell' + `-s' in `su'. + +`show-all' + `-A' in `cat'. + +`show-c-function' + `-p' in `diff'. + +`show-ends' + `-E' in `cat'. + +`show-function-line' + `-F' in `diff'. + +`show-tabs' + `-T' in `cat'. + +`silent' + Used in many programs to inhibit the usual output. *Note:* every + program accepting `--silent' should accept `--quiet' as a synonym. + +`size' + `-s' in `ls'. + +`socket' + Specify a file descriptor for a network server to use for its + socket, instead of opening and binding a new socket. This + provides a way to run, in a nonpriveledged process, a server that + normally needs a reserved port number. + +`sort' + Used in `ls'. + +`source' + `-W source' in `gawk'. + +`sparse' + `-S' in `tar'. + +`speed-large-files' + `-H' in `diff'. + +`split-at' + `-E' in `unshar'. + +`split-size-limit' + `-L' in `shar'. + +`squeeze-blank' + `-s' in `cat'. + +`start-delete' + `-w' in `wdiff'. + +`start-insert' + `-y' in `wdiff'. + +`starting-file' + Used in `tar' and `diff' to specify which file within a directory + to start processing with. + +`statistics' + `-s' in `wdiff'. + +`stdin-file-list' + `-S' in `shar'. + +`stop' + `-S' in Make. + +`strict' + `-s' in `recode'. + +`strip' + `-s' in `install'. + +`strip-all' + `-s' in `strip'. + +`strip-debug' + `-S' in `strip'. + +`submitter' + `-s' in `shar'. + +`suffix' + `-S' in `cp', `ln', `mv'. + +`suffix-format' + `-b' in `csplit'. + +`sum' + `-s' in `gprof'. + +`summarize' + `-s' in `du'. + +`symbolic' + `-s' in `ln'. + +`symbols' + Used in GDB and `objdump'. + +`synclines' + `-s' in `m4'. + +`sysname' + `-s' in `uname'. + +`tabs' + `-t' in `expand' and `unexpand'. + +`tabsize' + `-T' in `ls'. + +`terminal' + `-T' in `tput' and `ul'. `-t' in `wdiff'. + +`text' + `-a' in `diff'. + +`text-files' + `-T' in `shar'. + +`time' + Used in `ls' and `touch'. + +`to-stdout' + `-O' in `tar'. + +`total' + `-c' in `du'. + +`touch' + `-t' in Make, `ranlib', and `recode'. + +`trace' + `-t' in `m4'. + +`traditional' + `-t' in `hello'; `-W traditional' in `gawk'; `-G' in `ed', `m4', + and `ptx'. + +`tty' + Used in GDB. + +`typedefs' + `-t' in `ctags'. + +`typedefs-and-c++' + `-T' in `ctags'. + +`typeset-mode' + `-t' in `ptx'. + +`uncompress' + `-z' in `tar'. + +`unconditional' + `-u' in `cpio'. + +`undefine' + `-U' in `m4'. + +`undefined-only' + `-u' in `nm'. + +`update' + `-u' in `cp', `ctags', `mv', `tar'. + +`usage' + Used in `gawk'; same as `--help'. + +`uuencode' + `-B' in `shar'. + +`vanilla-operation' + `-V' in `shar'. + +`verbose' + Print more information about progress. Many programs support this. + +`verify' + `-W' in `tar'. + +`version' + Print the version number. + +`version-control' + `-V' in `cp', `ln', `mv'. + +`vgrind' + `-v' in `ctags'. + +`volume' + `-V' in `tar'. + +`what-if' + `-W' in Make. + +`whole-size-limit' + `-l' in `shar'. + +`width' + `-w' in `ls' and `ptx'. + +`word-regexp' + `-W' in `ptx'. + +`writable' + `-T' in `who'. + +`zeros' + `-z' in `gprof'. + + +File: standards.info, Node: Memory Usage, Prev: Option Table, Up: Program Behavior + +Memory Usage +============ + + If it typically uses just a few meg of memory, don't bother making +any effort to reduce memory usage. For example, if it is impractical +for other reasons to operate on files more than a few meg long, it is +reasonable to read entire input files into core to operate on them. + + However, for programs such as `cat' or `tail', that can usefully +operate on very large files, it is important to avoid using a technique +that would artificially limit the size of files it can handle. If a +program works by lines and could be applied to arbitrary user-supplied +input files, it should keep only a line in memory, because this is not +very hard and users will want to be able to operate on input files that +are bigger than will fit in core all at once. + + If your program creates complicated data structures, just make them +in core and give a fatal error if `malloc' returns zero. + + +File: standards.info, Node: Writing C, Next: Documentation, Prev: Program Behavior, Up: Top + +Making The Best Use of C +************************ + + This node provides advice on how best to use the C language when +writing GNU software. + +* Menu: + +* Formatting:: Formatting Your Source Code +* Comments:: Commenting Your Work +* Syntactic Conventions:: Clean Use of C Constructs +* Names:: Naming Variables and Functions +* System Portability:: Portability between different operating systems +* CPU Portability:: Supporting the range of CPU types +* System Functions:: Portability and "standard" library functions +* Internationalization:: Techniques for internationalization +* Mmap:: How you can safely use `mmap'. + + +File: standards.info, Node: Formatting, Next: Comments, Up: Writing C + +Formatting Your Source Code +=========================== + + It is important to put the open-brace that starts the body of a C +function in column zero, and avoid putting any other open-brace or +open-parenthesis or open-bracket in column zero. Several tools look +for open-braces in column zero to find the beginnings of C functions. +These tools will not work on code not formatted that way. + + It is also important for function definitions to start the name of +the function in column zero. This helps people to search for function +definitions, and may also help certain tools recognize them. Thus, the +proper format is this: + + static char * + concat (s1, s2) /* Name starts in column zero here */ + char *s1, *s2; + { /* Open brace in column zero here */ + ... + } + +or, if you want to use ANSI C, format the definition like this: + + static char * + concat (char *s1, char *s2) + { + ... + } + + In ANSI C, if the arguments don't fit nicely on one line, split it +like this: + + int + lots_of_args (int an_integer, long a_long, short a_short, + double a_double, float a_float) + ... + + For the body of the function, we prefer code formatted like this: + + if (x < foo (y, z)) + haha = bar[4] + 5; + else + { + while (z) + { + haha += foo (z, z); + z--; + } + return ++x + bar (); + } + + We find it easier to read a program when it has spaces before the +open-parentheses and after the commas. Especially after the commas. + + When you split an expression into multiple lines, split it before an +operator, not after one. Here is the right way: + + if (foo_this_is_long && bar > win (x, y, z) + && remaining_condition) + + Try to avoid having two operators of different precedence at the same +level of indentation. For example, don't write this: + + mode = (inmode[j] == VOIDmode + || GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j]) + ? outmode[j] : inmode[j]); + + Instead, use extra parentheses so that the indentation shows the +nesting: + + mode = ((inmode[j] == VOIDmode + || (GET_MODE_SIZE (outmode[j]) > GET_MODE_SIZE (inmode[j]))) + ? outmode[j] : inmode[j]); + + Insert extra parentheses so that Emacs will indent the code properly. +For example, the following indentation looks nice if you do it by hand, +but Emacs would mess it up: + + v = rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000 + + rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000; + + But adding a set of parentheses solves the problem: + + v = (rup->ru_utime.tv_sec*1000 + rup->ru_utime.tv_usec/1000 + + rup->ru_stime.tv_sec*1000 + rup->ru_stime.tv_usec/1000); + + Format do-while statements like this: + + do + { + a = foo (a); + } + while (a > 0); + + Please use formfeed characters (control-L) to divide the program into +pages at logical places (but not within a function). It does not matter +just how long the pages are, since they do not have to fit on a printed +page. The formfeeds should appear alone on lines by themselves. + + +File: standards.info, Node: Comments, Next: Syntactic Conventions, Prev: Formatting, Up: Writing C + +Commenting Your Work +==================== + + Every program should start with a comment saying briefly what it is +for. Example: `fmt - filter for simple filling of text'. + + Please write the comments in a GNU program in English, because +English is the one language that nearly all programmers in all +countries can read. If you do not write English well, please write +comments in English as well as you can, then ask other people to help +rewrite them. If you can't write comments in English, please find +someone to work with you and translate your comments into English. + + Please put a comment on each function saying what the function does, +what sorts of arguments it gets, and what the possible values of +arguments mean and are used for. It is not necessary to duplicate in +words the meaning of the C argument declarations, if a C type is being +used in its customary fashion. If there is anything nonstandard about +its use (such as an argument of type `char *' which is really the +address of the second character of a string, not the first), or any +possible values that would not work the way one would expect (such as, +that strings containing newlines are not guaranteed to work), be sure +to say so. + + Also explain the significance of the return value, if there is one. + + Please put two spaces after the end of a sentence in your comments, +so that the Emacs sentence commands will work. Also, please write +complete sentences and capitalize the first word. If a lower-case +identifier comes at the beginning of a sentence, don't capitalize it! +Changing the spelling makes it a different identifier. If you don't +like starting a sentence with a lower case letter, write the sentence +differently (e.g., "The identifier lower-case is ..."). + + The comment on a function is much clearer if you use the argument +names to speak about the argument values. The variable name itself +should be lower case, but write it in upper case when you are speaking +about the value rather than the variable itself. Thus, "the inode +number NODE_NUM" rather than "an inode". + + There is usually no purpose in restating the name of the function in +the comment before it, because the reader can see that for himself. +There might be an exception when the comment is so long that the +function itself would be off the bottom of the screen. + + There should be a comment on each static variable as well, like this: + + /* Nonzero means truncate lines in the display; + zero means continue them. */ + int truncate_lines; + + Every `#endif' should have a comment, except in the case of short +conditionals (just a few lines) that are not nested. The comment should +state the condition of the conditional that is ending, *including its +sense*. `#else' should have a comment describing the condition *and +sense* of the code that follows. For example: + + #ifdef foo + ... + #else /* not foo */ + ... + #endif /* not foo */ + #ifdef foo + ... + #endif /* foo */ + +but, by contrast, write the comments this way for a `#ifndef': + + #ifndef foo + ... + #else /* foo */ + ... + #endif /* foo */ + #ifndef foo + ... + #endif /* not foo */ + + +File: standards.info, Node: Syntactic Conventions, Next: Names, Prev: Comments, Up: Writing C + +Clean Use of C Constructs +========================= + + Please explicitly declare all arguments to functions. Don't omit +them just because they are `int's. + + Declarations of external functions and functions to appear later in +the source file should all go in one place near the beginning of the +file (somewhere before the first function definition in the file), or +else should go in a header file. Don't put `extern' declarations inside +functions. + + It used to be common practice to use the same local variables (with +names like `tem') over and over for different values within one +function. Instead of doing this, it is better declare a separate local +variable for each distinct purpose, and give it a name which is +meaningful. This not only makes programs easier to understand, it also +facilitates optimization by good compilers. You can also move the +declaration of each local variable into the smallest scope that includes +all its uses. This makes the program even cleaner. + + Don't use local variables or parameters that shadow global +identifiers. + + Don't declare multiple variables in one declaration that spans lines. +Start a new declaration on each line, instead. For example, instead of +this: + + int foo, + bar; + +write either this: + + int foo, bar; + +or this: + + int foo; + int bar; + +(If they are global variables, each should have a comment preceding it +anyway.) + + When you have an `if'-`else' statement nested in another `if' +statement, always put braces around the `if'-`else'. Thus, never write +like this: + + if (foo) + if (bar) + win (); + else + lose (); + +always like this: + + if (foo) + { + if (bar) + win (); + else + lose (); + } + + If you have an `if' statement nested inside of an `else' statement, +either write `else if' on one line, like this, + + if (foo) + ... + else if (bar) + ... + +with its `then'-part indented like the preceding `then'-part, or write +the nested `if' within braces like this: + + if (foo) + ... + else + { + if (bar) + ... + } + + Don't declare both a structure tag and variables or typedefs in the +same declaration. Instead, declare the structure tag separately and +then use it to declare the variables or typedefs. + + Try to avoid assignments inside `if'-conditions. For example, don't +write this: + + if ((foo = (char *) malloc (sizeof *foo)) == 0) + fatal ("virtual memory exhausted"); + +instead, write this: + + foo = (char *) malloc (sizeof *foo); + if (foo == 0) + fatal ("virtual memory exhausted"); + + Don't make the program ugly to placate `lint'. Please don't insert +any casts to `void'. Zero without a cast is perfectly fine as a null +pointer constant, except when calling a varargs function. + + +File: standards.info, Node: Names, Next: System Portability, Prev: Syntactic Conventions, Up: Writing C + +Naming Variables and Functions +============================== + + The names of global variables and functions in a program serve as +comments of a sort. So don't choose terse names--instead, look for +names that give useful information about the meaning of the variable or +function. In a GNU program, names should be English, like other +comments. + + Local variable names can be shorter, because they are used only +within one context, where (presumably) comments explain their purpose. + + Please use underscores to separate words in a name, so that the Emacs +word commands can be useful within them. Stick to lower case; reserve +upper case for macros and `enum' constants, and for name-prefixes that +follow a uniform convention. + + For example, you should use names like `ignore_space_change_flag'; +don't use names like `iCantReadThis'. + + Variables that indicate whether command-line options have been +specified should be named after the meaning of the option, not after +the option-letter. A comment should state both the exact meaning of +the option and its letter. For example, + + /* Ignore changes in horizontal whitespace (-b). */ + int ignore_space_change_flag; + + When you want to define names with constant integer values, use +`enum' rather than `#define'. GDB knows about enumeration constants. + + Use file names of 14 characters or less, to avoid creating gratuitous +problems on older System V systems. You can use the program `doschk' +to test for this. `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. + + +File: standards.info, Node: System Portability, Next: CPU Portability, Prev: Names, Up: Writing C + +Portability between System Types +================================ + + In the Unix world, "portability" refers to porting to different Unix +versions. For a GNU program, this kind of portability is desirable, but +not paramount. + + The primary purpose of GNU software is to run on top of the GNU +kernel, compiled with the GNU C compiler, on various types of CPU. The +amount and kinds of variation among GNU systems on different CPUs 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. + + The easiest way to achieve portability to most Unix-like systems is +to use Autoconf. It's unlikely that your program needs to know more +information about the host platform than Autoconf can provide, simply +because most of the programs that need such knowledge have already been +written. + + Avoid using the format of semi-internal data bases (e.g., +directories) when there is a higher-level alternative (`readdir'). + + As for systems that are not like Unix, such as MSDOS, Windows, the +Macintosh, VMS, and MVS, supporting them is 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. + + +File: standards.info, Node: CPU Portability, Next: System Functions, Prev: System Portability, Up: Writing C + +Portability between CPUs +======================== + + Even GNU systems will differ because of differences among CPU +types--for example, difference in byte ordering and alignment +requirements. It is absolutely essential to handle these differences. +However, don't make any effort to cater to the possibility that an +`int' will be less than 32 bits. We don't support 16-bit machines in +GNU. + + Don't assume that the address of an `int' object is also the address +of its least-significant byte. This is false on big-endian machines. +Thus, don't make the following mistake: + + int c; + ... + while ((c = getchar()) != EOF) + write(file_descriptor, &c, 1); + + When calling functions, you need not worry about the difference +between pointers of various types, or between pointers and integers. +On most machines, there's no difference anyway. As for the few +machines where there is a difference, all of them support ANSI C, so +you can use prototypes (conditionalized to be active only in ANSI C) to +make the code work on those systems. + + In certain cases, it is ok to pass integer and pointer arguments +indiscriminately to the same function, and use no prototype on any +system. For example, many GNU programs have error-reporting functions +that pass their arguments along to `printf' and friends: + + error (s, a1, a2, a3) + char *s; + int a1, a2, a3; + { + fprintf (stderr, "error: "); + fprintf (stderr, s, a1, a2, a3); + } + +In practice, this works on all machines, and it is much simpler than any +"correct" alternative. Be sure *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. + + +File: standards.info, Node: System Functions, Next: Internationalization, Prev: CPU Portability, Up: Writing C + +Calling System Functions +======================== + + C implementations differ substantially. ANSI C reduces but does not +eliminate the incompatibilities; meanwhile, many users wish to compile +GNU software with pre-ANSI compilers. This chapter gives +recommendations for how to use the more or less standard C library +functions to avoid unnecessary loss of portability. + + * Don't use the value of `sprintf'. It returns the number of + characters written on some systems, but not on all systems. + + * `main' should be declared to return type `int'. It should + terminate either by calling `exit' or by returning the integer + status code; make sure it cannot ever return an undefined value. + + * Don't declare system functions explicitly. + + Almost any declaration for a system function is wrong on some + system. To minimize conflicts, leave it to the system header + files to declare system functions. If the headers don't declare a + function, let it remain undeclared. + + While it may seem unclean to use a function without declaring it, + in practice this works fine for most system library functions on + the systems where this really happens; thus, the disadvantage is + only theoretical. By contrast, actual declarations have + frequently caused actual conflicts. + + * If you must declare a system function, don't specify the argument + types. Use an old-style declaration, not an ANSI prototype. The + more you specify about the function, the more likely a conflict. + + * In particular, don't unconditionally declare `malloc' or `realloc'. + + Most GNU programs use those functions just once, in functions + conventionally named `xmalloc' and `xrealloc'. These functions + call `malloc' and `realloc', respectively, and check the results. + + Because `xmalloc' and `xrealloc' are defined in your program, you + can declare them in other files without any risk of type conflict. + + On most systems, `int' is the same length as a pointer; thus, the + calls to `malloc' and `realloc' work fine. For the few + exceptional systems (mostly 64-bit machines), you can use + *conditionalized* declarations of `malloc' and `realloc'--or put + these declarations in configuration files specific to those + systems. + + * The string functions require special treatment. Some Unix systems + have a header file `string.h'; others have `strings.h'. Neither + file name is portable. There are two things you can do: use + Autoconf to figure out which file to include, or don't include + either file. + + * If you don't include either strings file, you can't get + declarations for the string functions from the header file in the + usual way. + + That causes less of a problem than you might think. The newer ANSI + string functions should be avoided anyway because many systems + still don't support them. The string functions you can use are + these: + + strcpy strncpy strcat strncat + strlen strcmp strncmp + strchr strrchr + + The copy and concatenate functions work fine without a declaration + as long as you don't use their values. Using their values without + a declaration fails on systems where the width of a pointer + differs from the width of `int', and perhaps in other cases. It + is trivial to avoid using their values, so do that. + + The compare functions and `strlen' work fine without a declaration + on most systems, possibly all the ones that GNU software runs on. + You may find it necessary to declare them *conditionally* on a few + systems. + + The search functions must be declared to return `char *'. Luckily, + there is no variation in the data type they return. But there is + variation in their names. Some systems give these functions the + names `index' and `rindex'; other systems use the names `strchr' + and `strrchr'. Some systems support both pairs of names, but + neither pair works on all systems. + + You should pick a single pair of names and use it throughout your + program. (Nowadays, it is better to choose `strchr' and `strrchr' + for new programs, since those are the standard ANSI names.) + Declare both of those names as functions returning `char *'. On + systems which don't support those names, define them as macros in + terms of the other pair. For example, here is what to put at the + beginning of your file (or in a header) if you want to use the + names `strchr' and `strrchr' throughout: + + #ifndef HAVE_STRCHR + #define strchr index + #endif + #ifndef HAVE_STRRCHR + #define strrchr rindex + #endif + + char *strchr (); + char *strrchr (); + + Here we assume that `HAVE_STRCHR' and `HAVE_STRRCHR' are macros +defined in systems where the corresponding functions exist. One way to +get them properly defined is to use Autoconf. + + +File: standards.info, Node: Internationalization, Next: Mmap, Prev: System Functions, Up: Writing C + +Internationalization +==================== + + GNU has a library called GNU gettext that makes it easy to translate +the messages in a program into various languages. You should use this +library in every program. Use English for the messages as they appear +in the program, and let gettext provide the way to translate them into +other languages. + + Using GNU gettext involves putting a call to the `gettext' macro +around each string that might need translation--like this: + + printf (gettext ("Processing file `%s'...")); + +This permits GNU gettext to replace the string `"Processing file +`%s'..."' with a translated version. + + Once a program uses gettext, please make a point of writing calls to +`gettext' when you add new strings that call for translation. + + Using GNU gettext in a package involves specifying a "text domain +name" for the package. The text domain name is used to separate the +translations for this package from the translations for other packages. +Normally, the text domain name should be the same as the name of the +package--for example, `fileutils' for the GNU file utilities. + + To enable gettext to work well, avoid writing code that makes +assumptions about the structure of words or sentences. When you want +the precise text of a sentence to vary depending on the data, use two or +more alternative string constants each containing a complete sentences, +rather than inserting conditionalized words or phrases into a single +sentence framework. + + Here is an example of what not to do: + + printf ("%d file%s processed", nfiles, + nfiles != 1 ? "s" : ""); + +The problem with that example is that it assumes that plurals are made +by adding `s'. If you apply gettext to the format string, like this, + + printf (gettext ("%d file%s processed"), nfiles, + nfiles != 1 ? "s" : ""); + +the message can use different words, but it will still be forced to use +`s' for the plural. Here is a better way: + + printf ((nfiles != 1 ? "%d files processed" + : "%d file processed"), + nfiles); + +This way, you can apply gettext to each of the two strings +independently: + + printf ((nfiles != 1 ? gettext ("%d files processed") + : gettext ("%d file processed")), + nfiles); + +This can be any method of forming the plural of the word for "file", and +also handles languages that require agreement in the word for +"processed". + + A similar problem appears at the level of sentence structure with +this code: + + printf ("# Implicit rule search has%s been done.\n", + f->tried_implicit ? "" : " not"); + +Adding `gettext' calls to this code cannot give correct results for all +languages, because negation in some languages requires adding words at +more than one place in the sentence. By contrast, adding `gettext' +calls does the job straightfowardly if the code starts out like this: + + printf (f->tried_implicit + ? "# Implicit rule search has been done.\n", + : "# Implicit rule search has not been done.\n"); + + +File: standards.info, Node: Mmap, Prev: Internationalization, Up: Writing C + +Mmap +==== + + Don't assume that `mmap' either works on all files or fails for all +files. It may work on some files and fail on others. + + The proper way to use `mmap' is to try it on the specific file for +which you want to use it--and if `mmap' doesn't work, fall back on +doing the job in another way using `read' and `write'. + + The reason this precaution is needed is that the GNU kernel (the +HURD) provides a user-extensible file system, in which there can be many +different kinds of "ordinary files." Many of them support `mmap', but +some do not. It is important to make programs handle all these kinds +of files. + + +File: standards.info, Node: Documentation, Next: Managing Releases, Prev: Writing C, Up: Top + +Documenting Programs +******************** + +* Menu: + +* GNU Manuals:: Writing proper manuals. +* Manual Structure Details:: Specific structure conventions. +* NEWS File:: NEWS files supplement manuals. +* Change Logs:: Recording Changes +* Man Pages:: Man pages are secondary. +* Reading other Manuals:: How far you can go in learning + from other manuals. + + +File: standards.info, Node: GNU Manuals, Next: Manual Structure Details, Up: Documentation + +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 `info' or +the Emacs Info subsystem (`C-h i'). + + Programmers often find it most natural to structure the documentation +following the structure of the implementation, which they know. But +this structure is not necessarily good for explaining how to use the +program; it may be irrelevant and confusing for a user. + + At every level, from the sentences in a paragraph to the grouping of +topics into separate manuals, the right way to structure documentation +is according to the concepts and questions that a user will have in mind +when reading it. Sometimes this structure of ideas matches the +structure of the implementation of the software being documented--but +often they are different. Often the most important part of learning to +write good documentation is learning to notice when you are structuring +the documentation like the implementation, and think about better +alternatives. + + For example, each program in the GNU system probably ought to be +documented in one manual; but this does not mean each program should +have its own manual. That would be following the structure of the +implementation, rather than the structure that helps the user +understand. + + Instead, each manual should cover a coherent *topic*. For example, +instead of a manual for `diff' and a manual for `diff3', we have one +manual for "comparison of files" which covers both of those programs, +as well as `cmp'. By documenting these programs together, we can make +the whole subject clearer. + + The manual which discusses a program should document all of the +program's command-line options and all of its commands. It should give +examples of their use. But don't organize the manual as a list of +features. Instead, organize it logically, by subtopics. Address the +questions that a user will ask when thinking about the job that the +program does. + + In general, a GNU manual should serve both as tutorial and reference. +It should be set up for convenient access to each topic through Info, +and for reading straight through (appendixes aside). A GNU manual +should give a good introduction to a beginner reading through from the +start, and should also provide all the details that hackers want. + + That is not as hard as it first sounds. Arrange each chapter as a +logical breakdown of its topic, but order the sections, and write their +text, so that reading the chapter straight through makes sense. Do +likewise when structuring the book into chapters, and when structuring a +section into paragraphs. The watchword is, *at each point, address the +most fundamental and important issue raised by the preceding text.* + + If necessary, add extra chapters at the beginning of the manual which +are purely tutorial and cover the basics of the subject. These provide +the framework for a beginner to understand the rest of the manual. The +Bison manual provides a good example of how to do this. + + 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 different from what we use in GNU manuals. + + 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. + + 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. + + +File: standards.info, Node: Manual Structure Details, Next: NEWS File, Prev: GNU Manuals, Up: Documentation + +Manual Structure Details +======================== + + The title page of the manual should state the version of the +programs or packages documented in the manual. The Top node of the +manual should also contain this information. If the manual is changing +more frequently than or independent of the program, also state a version +number for the manual in both of these places. + + Each program documented in the manual should should have a node named +`PROGRAM Invocation' or `Invoking PROGRAM'. This node (together with +its subnodes, if any) should describe the program's command line +arguments and how to run it (the sort of information people would look +in a man page for). Start with an `@example' containing a template for +all the options and arguments that the program uses. + + Alternatively, put a menu item in some menu whose item name fits one +of the above patterns. This identifies the node which that item points +to as the node for this purpose, regardless of the node's actual name. + + There will be automatic features for specifying a program name and +quickly reading just this part of its manual. + + If one manual describes several programs, it should have such a node +for each program described. + + +File: standards.info, Node: NEWS File, Next: Change Logs, Prev: Manual Structure Details, Up: Documentation + +The NEWS File +============= + + In addition to its manual, the package should have a file named +`NEWS' which contains a list of user-visible changes worth mentioning. +In each new release, add items to the front of the file and identify +the version they pertain to. Don't discard old items; leave them in +the file after the newer items. This way, a user upgrading from any +previous version can see what is new. + + If the `NEWS' file gets very long, move some of the older items into +a file named `ONEWS' and put a note at the end referring the user to +that file. + + +File: standards.info, Node: Change Logs, Next: Man Pages, Prev: NEWS File, Up: Documentation + +Change Logs +=========== + + Keep a change log to describe all the changes made to program source +files. The purpose of this is so that people investigating bugs in the +future will know about the changes that might have introduced the bug. +Often a new bug can be found by looking at what was recently changed. +More importantly, change logs can help you eliminate conceptual +inconsistencies between different parts of a program, by giving you a +history of how the conflicting concepts arose and who they came from. + +* Menu: + +* Change Log Concepts:: +* Style of Change Logs:: +* Simple Changes:: +* Conditional Changes:: + + +File: standards.info, Node: Change Log Concepts, Next: Style of Change Logs, Up: Change Logs + +Change Log Concepts +------------------- + + You can think of the change log as a conceptual "undo list" which +explains how earlier versions were different from the current version. +People can see the current version; they don't need the change log to +tell them what is in it. What they want from a change log is a clear +explanation of how the earlier version differed. + + The change log file is normally called `ChangeLog' and covers an +entire directory. Each directory can have its own change log, or a +directory can use the change log of its parent directory-it's up to you. + + Another alternative is to record change log information with a +version control system such as RCS or CVS. This can be converted +automatically to a `ChangeLog' file. + + There's no need to describe the full purpose of the changes or how +they work together. If you think that a change calls for explanation, +you're probably right. Please do explain it--but please put the +explanation in comments in the code, where people will see it whenever +they see the code. For example, "New function" is enough for the +change log when you add a function, because there should be a comment +before the function definition to explain what it does. + + However, sometimes it is useful to write one line to describe the +overall purpose of a batch of changes. + + The easiest way to add an entry to `ChangeLog' is with the Emacs +command `M-x add-change-log-entry'. An entry should have an asterisk, +the name of the changed file, and then in parentheses the name of the +changed functions, variables or whatever, followed by a colon. Then +describe the changes you made to that function or variable. + + +File: standards.info, Node: Style of Change Logs, Next: Simple Changes, Prev: Change Log Concepts, Up: Change Logs + +Style of Change Logs +-------------------- + + Here are some examples of change log entries: + + * register.el (insert-register): Return nil. + (jump-to-register): Likewise. + + * sort.el (sort-subr): Return nil. + + * tex-mode.el (tex-bibtex-file, tex-file, tex-region): + Restart the tex shell if process is gone or stopped. + (tex-shell-running): New function. + + * expr.c (store_one_arg): Round size up for move_block_to_reg. + (expand_call): Round up when emitting USE insns. + * stmt.c (assign_parms): Round size up for move_block_from_reg. + + It's important to name the changed function or variable in full. +Don't abbreviate function or variable names, and don't combine them. +Subsequent maintainers will often search for a function name to find all +the change log entries that pertain to it; if you abbreviate the name, +they won't find it when they search. + + For example, some people are tempted to abbreviate groups of function +names by writing `* register.el ({insert,jump-to}-register)'; this is +not a good idea, since searching for `jump-to-register' or +`insert-register' would not find that entry. + + Separate unrelated change log entries with blank lines. When two +entries represent parts of the same change, so that they work together, +then don't put blank lines between them. Then you can omit the file +name and the asterisk when successive entries are in the same file. + + +File: standards.info, Node: Simple Changes, Next: Conditional Changes, Prev: Style of Change Logs, Up: Change Logs + +Simple Changes +-------------- + + Certain simple kinds of changes don't need much detail in the change +log. + + When you change the calling sequence of a function in a simple +fashion, and you change all the callers of the function, 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." + + * keyboard.c (Fcommand_execute): New arg SPECIAL. + All callers changed. + + When you change just comments or doc strings, it is enough to write +an entry for the file, without mentioning the functions. Just "Doc +fixes" is enough for the change log. + + There's no need to make change log entries for documentation files. +This is because documentation is not susceptible to bugs that are hard +to fix. Documentation does not consist of parts that must interact in a +precisely engineered fashion. To correct an error, you need not know +the history of the erroneous passage; it is enough to compare what the +documentation says with the way the program actually works. + + +File: standards.info, Node: Conditional Changes, Prev: Simple Changes, Up: Change Logs + +Conditional Changes +------------------- + + C programs often contain compile-time `#if' conditionals. Many +changes are conditional; sometimes you add a new definition which is +entirely contained in a conditional. It is very useful to indicate in +the change log the conditions for which the change applies. + + Our convention for indicating conditional changes is to use square +brackets around the name of the condition. + + Here is a simple example, describing a change which is conditional +but does not have a function or entity name associated with it: + + * xterm.c [SOLARIS2]: Include string.h. + + Here is an entry describing a new definition which is entirely +conditional. This new definition for the macro `FRAME_WINDOW_P' is +used only when `HAVE_X_WINDOWS' is defined: + + * frame.h [HAVE_X_WINDOWS] (FRAME_WINDOW_P): Macro defined. + + Here is an entry for a change within the function `init_display', +whose definition as a whole is unconditional, but the changes themselves +are contained in a `#ifdef HAVE_LIBNCURSES' conditional: + + * dispnew.c (init_display) [HAVE_LIBNCURSES]: If X, call tgetent. + + Here is an entry for a change that takes affect only when a certain +macro is *not* defined: + + (gethostname) [!HAVE_SOCKETS]: Replace with winsock version. + + +File: standards.info, Node: Man Pages, Next: Reading other Manuals, Prev: Change Logs, Up: Documentation + +Man Pages +========= + + In the GNU project, man pages are secondary. It is not necessary or +expected for every GNU program to have a man page, but some of them do. +It's your choice whether to include a man page in your program. + + When you make this decision, consider that supporting a man page +requires continual effort each time the program is changed. The time +you spend on the man page is time taken away from more useful work. + + For a simple program which changes little, updating the man page may +be a small job. Then there is little reason not to include a man page, +if you have one. + + For a large program that changes a great deal, updating a man page +may be a substantial burden. If a user offers to donate a man page, +you may find this gift costly to accept. It may be better to refuse +the man page unless the same person agrees to take full responsibility +for maintaining it--so that you can wash your hands of it entirely. If +this volunteer later ceases to do the job, then don't feel obliged to +pick it up yourself; it may be better to withdraw the man page from the +distribution until someone else agrees to update it. + + When a program changes only a little, you may feel that the +discrepancies are small enough that the man page remains useful without +updating. If so, put a prominent note near the beginning of the man +page explaining that you don't maintain it and that the Texinfo manual +is more authoritative. The note should say how to access the Texinfo +documentation. + + +File: standards.info, Node: Reading other Manuals, Prev: Man Pages, Up: Documentation + +Reading other Manuals +===================== + + There may be non-free books or documentation files that describe the +program you are documenting. + + It is ok to use these documents for reference, just as the author of +a new algebra textbook can read other books on algebra. A large portion +of any non-fiction book consists of facts, in this case facts about how +a certain program works, and these facts are necessarily the same for +everyone who writes about the subject. But be careful not to copy your +outline structure, wording, tables or examples from preexisting non-free +documentation. Copying from free documentation may be ok; please check +with the FSF about the individual case. + + +File: standards.info, Node: Managing Releases, Prev: Documentation, Up: Top + +The Release Process +******************* + + Making a release is more than just bundling up your source files in a +tar file and putting it up for FTP. You should set up your software so +that it can be configured to run on a variety of systems. Your Makefile +should conform to the GNU standards described below, and your directory +layout should also conform to the standards discussed below. Doing so +makes it easy to include your package into the larger framework of all +GNU software. + +* Menu: + +* Configuration:: How Configuration Should Work +* Makefile Conventions:: Makefile Conventions +* Releases:: Making Releases + + +File: standards.info, Node: Configuration, Next: Makefile Conventions, Up: Managing Releases + +How Configuration Should Work +============================= + + Each GNU distribution should come with a shell script named +`configure'. This script is given arguments which describe the kind of +machine and system you want to compile the program for. + + The `configure' script must record the configuration options so that +they affect compilation. + + One way to do this is to make a link from a standard name such as +`config.h' to the proper configuration file for the chosen system. If +you use this technique, the distribution should *not* contain a file +named `config.h'. This is so that people won't be able to build the +program without configuring it first. + + Another thing that `configure' can do is to edit the Makefile. If +you do this, the distribution should *not* contain a file named +`Makefile'. Instead, it should include a file `Makefile.in' which +contains the input used for editing. Once again, this is so that people +won't be able to build the program without configuring it first. + + If `configure' does write the `Makefile', then `Makefile' should +have a target named `Makefile' which causes `configure' to be rerun, +setting up the same configuration that was set up last time. The files +that `configure' reads should be listed as dependencies of `Makefile'. + + All the files which are output from the `configure' script should +have comments at the beginning explaining that they were generated +automatically using `configure'. This is so that users won't think of +trying to edit them by hand. + + The `configure' script should write a file named `config.status' +which describes which configuration options were specified when the +program was last configured. This file should be a shell script which, +if run, will recreate the same configuration. + + The `configure' script should accept an option of the form +`--srcdir=DIRNAME' to specify the directory where sources are found (if +it is not the current directory). This makes it possible to build the +program in a separate directory, so that the actual source directory is +not modified. + + If the user does not specify `--srcdir', then `configure' should +check both `.' and `..' to see if it can find the sources. If it finds +the sources in one of these places, it should use them from there. +Otherwise, it should report that it cannot find the sources, and should +exit with nonzero status. + + Usually the easy way to support `--srcdir' is by editing a +definition of `VPATH' into the Makefile. Some rules may need to refer +explicitly to the specified source directory. To make this possible, +`configure' can add to the Makefile a variable named `srcdir' whose +value is precisely the specified directory. + + The `configure' script should also take an argument which specifies +the type of system to build the program for. This argument should look +like this: + + CPU-COMPANY-SYSTEM + + For example, a Sun 3 might be `m68k-sun-sunos4.1'. + + The `configure' script needs to be able to decode all plausible +alternatives for how to describe a machine. Thus, `sun3-sunos4.1' +would be a valid alias. For many programs, `vax-dec-ultrix' would be +an alias for `vax-dec-bsd', simply because the differences between +Ultrix and BSD are rarely noticeable, but a few programs might need to +distinguish them. + + There is a shell script called `config.sub' that you can use as a +subroutine to validate system types and canonicalize aliases. + + Other options are permitted to specify in more detail the software +or hardware present on the machine, and include or exclude optional +parts of the package: + +`--enable-FEATURE[=PARAMETER]' + Configure the package to build and install an optional user-level + facility called FEATURE. This allows users to choose which + optional features to include. Giving an optional PARAMETER of + `no' should omit FEATURE, if it is built by default. + + No `--enable' option should *ever* cause one feature to replace + another. No `--enable' option should ever substitute one useful + behavior for another useful behavior. The only proper use for + `--enable' is for questions of whether to build part of the program + or exclude it. + +`--with-PACKAGE' + The package PACKAGE will be installed, so configure this package + to work with PACKAGE. + + Possible values of PACKAGE include `gnu-as' (or `gas'), `gnu-ld', + `gnu-libc', `gdb', `x', and `x-toolkit'. + + Do not use a `--with' option to specify the file name to use to + find certain files. That is outside the scope of what `--with' + options are for. + +`--nfp' + The target machine has no floating point processor. + +`--gas' + The target machine assembler is GAS, the GNU assembler. This is + obsolete; users should use `--with-gnu-as' instead. + +`--x' + The target machine has the X Window System installed. This is + obsolete; users should use `--with-x' instead. + + All `configure' scripts should accept all of these "detail" options, +whether or not they make any difference to the particular package at +hand. In particular, they should accept any option that starts with +`--with-' or `--enable-'. This is so users will be able to configure +an entire GNU source tree at once with a single set of options. + + You will note that the categories `--with-' and `--enable-' are +narrow: they *do not* provide a place for any sort of option you might +think of. That is deliberate. We want to limit the possible +configuration options in GNU software. We do not want GNU programs to +have idiosyncratic configuration options. + + Packages that perform part of the compilation process may support +cross-compilation. In such a case, the host and target machines for +the program may be different. The `configure' script should normally +treat the specified type of system as both the host and the target, +thus producing a program which works for the same type of machine that +it runs on. + + The way to build a cross-compiler, cross-assembler, or what have +you, is to specify the option `--host=HOSTTYPE' when running +`configure'. This specifies the host system without changing the type +of target system. The syntax for HOSTTYPE is the same as described +above. + + Bootstrapping a cross-compiler requires compiling it on a machine +other than the host it will run on. Compilation packages accept a +configuration option `--build=HOSTTYPE' for specifying the +configuration on which you will compile them, in case that is different +from the host. + + Programs for which cross-operation is not meaningful need not accept +the `--host' option, because configuring an entire operating system for +cross-operation is not a meaningful thing. + + Some programs have ways of configuring themselves automatically. If +your program is set up to do this, your `configure' script can simply +ignore most of its arguments. + + +File: standards.info, Node: Makefile Conventions, Next: Releases, Prev: Configuration, Up: Managing Releases + +Makefile Conventions +==================== + + This node describes conventions for writing the Makefiles for GNU +programs. + +* Menu: + +* Makefile Basics:: General Conventions for Makefiles +* Utilities in Makefiles:: Utilities in Makefiles +* Command Variables:: Variables for Specifying Commands +* Directory Variables:: Variables for Installation Directories +* Standard Targets:: Standard Targets for Users +* Install Command Categories:: Three categories of commands in the `install' + rule: normal, pre-install and post-install. + + +File: standards.info, Node: Makefile Basics, Next: Utilities in Makefiles, Up: Makefile Conventions + +General Conventions for Makefiles +--------------------------------- + + Every Makefile should contain this line: + + SHELL = /bin/sh + +to avoid trouble on systems where the `SHELL' variable might be +inherited from the environment. (This is never a problem with GNU +`make'.) + + Different `make' programs have incompatible suffix lists and +implicit rules, and this sometimes creates confusion or misbehavior. So +it is a good idea to set the suffix list explicitly using only the +suffixes you need in the particular Makefile, like this: + + .SUFFIXES: + .SUFFIXES: .c .o + +The first line clears out the suffix list, the second introduces all +suffixes which may be subject to implicit rules in this Makefile. + + Don't assume that `.' is in the path for command execution. When +you need to run programs that are a part of your package during the +make, please make sure that it uses `./' if the program is built as +part of the make or `$(srcdir)/' if the file is an unchanging part of +the source code. Without one of these prefixes, the current search +path is used. + + The distinction between `./' (the "build directory") and +`$(srcdir)/' (the "source directory") is important because users can +build in a separate directory using the `--srcdir' option to +`configure'. A rule of the form: + + foo.1 : foo.man sedscript + sed -e sedscript foo.man > foo.1 + +will fail when the build directory is not the source directory, because +`foo.man' and `sedscript' are in the the source directory. + + When using GNU `make', relying on `VPATH' to find the source file +will work in the case where there is a single dependency file, since +the `make' automatic variable `$<' will represent the source file +wherever it is. (Many versions of `make' set `$<' only in implicit +rules.) A Makefile target like + + foo.o : bar.c + $(CC) -I. -I$(srcdir) $(CFLAGS) -c bar.c -o foo.o + +should instead be written as + + foo.o : bar.c + $(CC) -I. -I$(srcdir) $(CFLAGS) -c $< -o $@ + +in order to allow `VPATH' to work correctly. When the target has +multiple dependencies, using an explicit `$(srcdir)' is the easiest way +to make the rule work well. For example, the target above for `foo.1' +is best written as: + + foo.1 : foo.man sedscript + sed -e $(srcdir)/sedscript $(srcdir)/foo.man > $@ + + GNU distributions usually contain some files which are not source +files--for example, Info files, and the output from Autoconf, Automake, +Bison or Flex. Since these files normally appear in the source +directory, they should always appear in the source directory, not in the +build directory. So Makefile rules to update them should put the +updated files in the source directory. + + However, if a file does not appear in the distribution, then the +Makefile should not put it in the source directory, because building a +program in ordinary circumstances should not modify the source directory +in any way. + + Try to make the build and installation targets, at least (and all +their subtargets) work correctly with a parallel `make'. + + +File: standards.info, Node: Utilities in Makefiles, Next: Command Variables, Prev: Makefile Basics, Up: Makefile Conventions + +Utilities in Makefiles +---------------------- + + Write the Makefile commands (and any shell scripts, such as +`configure') to run in `sh', not in `csh'. Don't use any special +features of `ksh' or `bash'. + + The `configure' script and the Makefile rules for building and +installation should not use any utilities directly except these: + + cat cmp cp diff echo egrep expr false grep install-info + ln ls mkdir mv pwd rm rmdir sed sleep sort tar test touch true + + The compression program `gzip' can be used in the `dist' rule. + + Stick to the generally supported options for these programs. For +example, don't use `mkdir -p', convenient as it may be, because most +systems don't support it. + + It is a good idea to avoid creating symbolic links in makefiles, +since a few systems don't support them. + + The Makefile rules for building and installation can also use +compilers and related programs, but should do so via `make' variables +so that the user can substitute alternatives. Here are some of the +programs we mean: + + ar bison cc flex install ld ldconfig lex + make makeinfo ranlib texi2dvi yacc + + Use the following `make' variables to run those programs: + + $(AR) $(BISON) $(CC) $(FLEX) $(INSTALL) $(LD) $(LDCONFIG) $(LEX) + $(MAKE) $(MAKEINFO) $(RANLIB) $(TEXI2DVI) $(YACC) + + When you use `ranlib' or `ldconfig', you should make sure nothing +bad happens if the system does not have the program in question. +Arrange to ignore an error from that command, and print a message before +the command to tell the user that failure of this command does not mean +a problem. (The Autoconf `AC_PROG_RANLIB' macro can help with this.) + + If you use symbolic links, you should implement a fallback for +systems that don't have symbolic links. + + Additional utilities that can be used via Make variables are: + + chgrp chmod chown mknod + + It is ok to use other utilities in Makefile portions (or scripts) +intended only for particular systems where you know those utilities +exist. + + +File: standards.info, Node: Command Variables, Next: Directory Variables, Prev: Utilities in Makefiles, Up: Makefile Conventions + +Variables for Specifying Commands +--------------------------------- + + Makefiles should provide variables for overriding certain commands, +options, and so on. + + In particular, you should run most utility programs via variables. +Thus, if you use Bison, have a variable named `BISON' whose default +value is set with `BISON = bison', and refer to it with `$(BISON)' +whenever you need to use Bison. + + File management utilities such as `ln', `rm', `mv', and so on, need +not be referred to through variables in this way, since users don't +need to replace them with other programs. + + Each program-name variable should come with an options variable that +is used to supply options to the program. Append `FLAGS' to the +program-name variable name to get the options variable name--for +example, `BISONFLAGS'. (The names `CFLAGS' for the C compiler, +`YFLAGS' for yacc, and `LFLAGS' for lex, are exceptions to this rule, +but we keep them because they are standard.) Use `CPPFLAGS' in any +compilation command that runs the preprocessor, and use `LDFLAGS' in +any compilation command that does linking as well as in any direct use +of `ld'. + + If there are C compiler options that *must* be used for proper +compilation of certain files, do not include them in `CFLAGS'. Users +expect to be able to specify `CFLAGS' freely themselves. Instead, +arrange to pass the necessary options to the C compiler independently +of `CFLAGS', by writing them explicitly in the compilation commands or +by defining an implicit rule, like this: + + CFLAGS = -g + ALL_CFLAGS = -I. $(CFLAGS) + .c.o: + $(CC) -c $(CPPFLAGS) $(ALL_CFLAGS) $< + + Do include the `-g' option in `CFLAGS', because that is not +*required* for proper compilation. You can consider it a default that +is only recommended. If the package is set up so that it is compiled +with GCC by default, then you might as well include `-O' in the default +value of `CFLAGS' as well. + + Put `CFLAGS' last in the compilation command, after other variables +containing compiler options, so the user can use `CFLAGS' to override +the others. + + `CFLAGS' should be used in every invocation of the C compiler, both +those which do compilation and those which do linking. + + Every Makefile should define the variable `INSTALL', which is the +basic command for installing a file into the system. + + Every Makefile should also define the variables `INSTALL_PROGRAM' +and `INSTALL_DATA'. (The default for each of these should be +`$(INSTALL)'.) Then it should use those variables as the commands for +actual installation, for executables and nonexecutables respectively. +Use these variables as follows: + + $(INSTALL_PROGRAM) foo $(bindir)/foo + $(INSTALL_DATA) libfoo.a $(libdir)/libfoo.a + +Always use a file name, not a directory name, as the second argument of +the installation commands. Use a separate command for each file to be +installed. + + +File: standards.info, Node: Directory Variables, Next: Standard Targets, Prev: Command Variables, Up: Makefile Conventions + +Variables for Installation Directories +-------------------------------------- + + Installation directories should always be named by variables, so it +is easy to install in a nonstandard place. The standard names for these +variables are described below. They are based on a standard filesystem +layout; variants of it are used in SVR4, 4.4BSD, Linux, Ultrix v4, and +other modern operating systems. + + These two variables set the root for the installation. All the other +installation directories should be subdirectories of one of these two, +and nothing should be directly installed into these two directories. + +`prefix' + A prefix used in constructing the default values of the variables + listed below. The default value of `prefix' should be + `/usr/local'. When building the complete GNU system, the prefix + will be empty and `/usr' will be a symbolic link to `/'. (If you + are using Autoconf, write it as `@prefix@'.) + +`exec_prefix' + A prefix used in constructing the default values of some of the + variables listed below. The default value of `exec_prefix' should + be `$(prefix)'. (If you are using Autoconf, write it as + `@exec_prefix@'.) + + Generally, `$(exec_prefix)' is used for directories that contain + machine-specific files (such as executables and subroutine + libraries), while `$(prefix)' is used directly for other + directories. + + Executable programs are installed in one of the following +directories. + +`bindir' + The directory for installing executable programs that users can + run. This should normally be `/usr/local/bin', but write it as + `$(exec_prefix)/bin'. (If you are using Autoconf, write it as + `@bindir@'.) + +`sbindir' + The directory for installing executable programs that can be run + from the shell, but are only generally useful to system + administrators. This should normally be `/usr/local/sbin', but + write it as `$(exec_prefix)/sbin'. (If you are using Autoconf, + write it as `@sbindir@'.) + +`libexecdir' + The directory for installing executable programs to be run by other + programs rather than by users. This directory should normally be + `/usr/local/libexec', but write it as `$(exec_prefix)/libexec'. + (If you are using Autoconf, write it as `@libexecdir@'.) + + Data files used by the program during its execution are divided into +categories in two ways. + + * Some files are normally modified by programs; others are never + normally modified (though users may edit some of these). + + * Some files are architecture-independent and can be shared by all + machines at a site; some are architecture-dependent and can be + shared only by machines of the same kind and operating system; + others may never be shared between two machines. + + This makes for six different possibilities. However, we want to +discourage the use of architecture-dependent files, aside from object +files and libraries. It is much cleaner to make other data files +architecture-independent, and it is generally not hard. + + Therefore, here are the variables Makefiles should use to specify +directories: + +`datadir' + The directory for installing read-only architecture independent + data files. This should normally be `/usr/local/share', but write + it as `$(prefix)/share'. (If you are using Autoconf, write it as + `@datadir@'.) As a special exception, see `$(infodir)' and + `$(includedir)' below. + +`sysconfdir' + The directory for installing read-only data files that pertain to a + single machine-that is to say, files for configuring a host. + Mailer and network configuration files, `/etc/passwd', and so + forth belong here. All the files in this directory should be + ordinary ASCII text files. This directory should normally be + `/usr/local/etc', but write it as `$(prefix)/etc'. (If you are + using Autoconf, write it as `@sysconfdir@'.) + + Do not install executables here in this directory (they probably + belong in `$(libexecdir)' or `$(sbindir)'). Also do not install + files that are modified in the normal course of their use (programs + whose purpose is to change the configuration of the system + excluded). Those probably belong in `$(localstatedir)'. + +`sharedstatedir' + The directory for installing architecture-independent data files + which the programs modify while they run. This should normally be + `/usr/local/com', but write it as `$(prefix)/com'. (If you are + using Autoconf, write it as `@sharedstatedir@'.) + +`localstatedir' + The directory for installing data files which the programs modify + while they run, and that pertain to one specific machine. Users + should never need to modify files in this directory to configure + the package's operation; put such configuration information in + separate files that go in `$(datadir)' or `$(sysconfdir)'. + `$(localstatedir)' should normally be `/usr/local/var', but write + it as `$(prefix)/var'. (If you are using Autoconf, write it as + `@localstatedir@'.) + +`libdir' + The directory for object files and libraries of object code. Do + not install executables here, they probably ought to go in + `$(libexecdir)' instead. The value of `libdir' should normally be + `/usr/local/lib', but write it as `$(exec_prefix)/lib'. (If you + are using Autoconf, write it as `@libdir@'.) + +`infodir' + The directory for installing the Info files for this package. By + default, it should be `/usr/local/info', but it should be written + as `$(prefix)/info'. (If you are using Autoconf, write it as + `@infodir@'.) + +`lispdir' + The directory for installing any Emacs Lisp files in this package. + By default, it should be `/usr/local/share/emacs/site-lisp', but + it should be written as `$(prefix)/share/emacs/site-lisp'. + + If you are using Autoconf, write the default as `@lispdir@'. In + order to make `@lispdir@' work, you need the following lines in + your `configure.in' file: + + lispdir='${datadir}/emacs/site-lisp' + AC_SUBST(lispdir) + +`includedir' + The directory for installing header files to be included by user + programs with the C `#include' preprocessor directive. This + should normally be `/usr/local/include', but write it as + `$(prefix)/include'. (If you are using Autoconf, write it as + `@includedir@'.) + + Most compilers other than GCC do not look for header files in + directory `/usr/local/include'. So installing the header files + this way is only useful with GCC. Sometimes this is not a problem + because some libraries are only really intended to work with GCC. + But some libraries are intended to work with other compilers. + They should install their header files in two places, one + specified by `includedir' and one specified by `oldincludedir'. + +`oldincludedir' + The directory for installing `#include' header files for use with + compilers other than GCC. This should normally be `/usr/include'. + (If you are using Autoconf, you can write it as `@oldincludedir@'.) + + The Makefile commands should check whether the value of + `oldincludedir' is empty. If it is, they should not try to use + it; they should cancel the second installation of the header files. + + A package should not replace an existing header in this directory + unless the header came from the same package. Thus, if your Foo + package provides a header file `foo.h', then it should install the + header file in the `oldincludedir' directory if either (1) there + is no `foo.h' there or (2) the `foo.h' that exists came from the + Foo package. + + To tell whether `foo.h' came from the Foo package, put a magic + string in the file--part of a comment--and `grep' for that string. + + Unix-style man pages are installed in one of the following: + +`mandir' + The top-level directory for installing the man pages (if any) for + this package. It will normally be `/usr/local/man', but you should + write it as `$(prefix)/man'. (If you are using Autoconf, write it + as `@mandir@'.) + +`man1dir' + The directory for installing section 1 man pages. Write it as + `$(mandir)/man1'. + +`man2dir' + The directory for installing section 2 man pages. Write it as + `$(mandir)/man2' + +`...' + *Don't make the primary documentation for any GNU software be a + man page. Write a manual in Texinfo instead. Man pages are just + for the sake of people running GNU software on Unix, which is a + secondary application only.* + +`manext' + The file name extension for the installed man page. This should + contain a period followed by the appropriate digit; it should + normally be `.1'. + +`man1ext' + The file name extension for installed section 1 man pages. + +`man2ext' + The file name extension for installed section 2 man pages. + +`...' + Use these names instead of `manext' if the package needs to + install man pages in more than one section of the manual. + + And finally, you should set the following variable: + +`srcdir' + The directory for the sources being compiled. The value of this + variable is normally inserted by the `configure' shell script. + (If you are using Autconf, use `srcdir = @srcdir@'.) + + For example: + + # Common prefix for installation directories. + # NOTE: This directory must exist when you start the install. + prefix = /usr/local + exec_prefix = $(prefix) + # Where to put the executable for the command `gcc'. + bindir = $(exec_prefix)/bin + # Where to put the directories used by the compiler. + libexecdir = $(exec_prefix)/libexec + # Where to put the Info files. + infodir = $(prefix)/info + + If your program installs a large number of files into one of the +standard user-specified directories, it might be useful to group them +into a subdirectory particular to that program. If you do this, you +should write the `install' rule to create these subdirectories. + + Do not expect the user to include the subdirectory name in the value +of any of the variables listed above. The idea of having a uniform set +of variable names for installation directories is to enable the user to +specify the exact same values for several different GNU packages. In +order for this to be useful, all the packages must be designed so that +they will work sensibly when the user does so. + + +File: standards.info, Node: Standard Targets, Next: Install Command Categories, Prev: Directory Variables, Up: Makefile Conventions + +Standard Targets for Users +-------------------------- + + All GNU programs should have the following targets in their +Makefiles: + +`all' + Compile the entire program. This should be the default target. + This target need not rebuild any documentation files; Info files + should normally be included in the distribution, and DVI files + should be made only when explicitly asked for. + + By default, the Make rules should compile and link with `-g', so + that executable programs have debugging symbols. Users who don't + mind being helpless can strip the executables later if they wish. + +`install' + Compile the program and copy the executables, libraries, and so on + to the file names where they should reside for actual use. If + there is a simple test to verify that a program is properly + installed, this target should run that test. + + Do not strip executables when installing them. Devil-may-care + users can use the `install-strip' target to do that. + + If possible, write the `install' target rule so that it does not + modify anything in the directory where the program was built, + provided `make all' has just been done. This is convenient for + building the program under one user name and installing it under + another. + + The commands should create all the directories in which files are + to be installed, if they don't already exist. This includes the + directories specified as the values of the variables `prefix' and + `exec_prefix', as well as all subdirectories that are needed. One + way to do this is by means of an `installdirs' target as described + below. + + Use `-' before any command for installing a man page, so that + `make' will ignore any errors. This is in case there are systems + that don't have the Unix man page documentation system installed. + + The way to install Info files is to copy them into `$(infodir)' + with `$(INSTALL_DATA)' (*note Command Variables::.), and then run + the `install-info' program if it is present. `install-info' is a + program that edits the Info `dir' file to add or update the menu + entry for the given Info file; it is part of the Texinfo package. + Here is a sample rule to install an Info file: + + $(infodir)/foo.info: foo.info + $(POST_INSTALL) + # There may be a newer info file in . than in srcdir. + -if test -f foo.info; then d=.; \ + else d=$(srcdir); fi; \ + $(INSTALL_DATA) $$d/foo.info $@; \ + # Run install-info only if it exists. + # Use `if' instead of just prepending `-' to the + # line so we notice real errors from install-info. + # We use `$(SHELL) -c' because some shells do not + # fail gracefully when there is an unknown command. + if $(SHELL) -c 'install-info --version' \ + >/dev/null 2>&1; then \ + install-info --dir-file=$(infodir)/dir \ + $(infodir)/foo.info; \ + else true; fi + + When writing the `install' target, you must classify all the + commands into three categories: normal ones, "pre-installation" + commands and "post-installation" commands. *Note Install Command + Categories::. + +`uninstall' + Delete all the installed files--the copies that the `install' + target creates. + + This rule should not modify the directories where compilation is + done, only the directories where files are installed. + + The uninstallation commands are divided into three categories, + just like the installation commands. *Note Install Command + Categories::. + +`install-strip' + Like `install', but strip the executable files while installing + them. In many cases, the definition of this target can be very + simple: + + install-strip: + $(MAKE) INSTALL_PROGRAM='$(INSTALL_PROGRAM) -s' \ + install + + Normally we do not recommend stripping an executable unless you + are sure the program has no bugs. However, it can be reasonable + to install a stripped executable for actual execution while saving + the unstripped executable elsewhere in case there is a bug. + +`clean' + Delete all files from the current directory that are normally + created by building the program. Don't delete the files that + record the configuration. Also preserve files that could be made + by building, but normally aren't because the distribution comes + with them. + + Delete `.dvi' files here if they are not part of the distribution. + +`distclean' + Delete all files from the current directory that are created by + configuring or building the program. If you have unpacked the + source and built the program without creating any other files, + `make distclean' should leave only the files that were in the + distribution. + +`mostlyclean' + Like `clean', but may refrain from deleting a few files that people + normally don't want to recompile. For example, the `mostlyclean' + target for GCC does not delete `libgcc.a', because recompiling it + is rarely necessary and takes a lot of time. + +`maintainer-clean' + Delete almost everything from the current directory that can be + reconstructed with this Makefile. This typically includes + everything deleted by `distclean', plus more: C source files + produced by Bison, tags tables, Info files, and so on. + + The reason we say "almost everything" is that running the command + `make maintainer-clean' should not delete `configure' even if + `configure' can be remade using a rule in the Makefile. More + generally, `make maintainer-clean' should not delete anything that + needs to exist in order to run `configure' and then begin to build + the program. This is the only exception; `maintainer-clean' should + delete everything else that can be rebuilt. + + The `maintainer-clean' target is intended to be used by a + maintainer of the package, not by ordinary users. You may need + special tools to reconstruct some of the files that `make + maintainer-clean' deletes. Since these files are normally + included in the distribution, we don't take care to make them easy + to reconstruct. If you find you need to unpack the full + distribution again, don't blame us. + + To help make users aware of this, the commands for the special + `maintainer-clean' target should start with these two: + + @echo 'This command is intended for maintainers to use; it' + @echo 'deletes files that may need special tools to rebuild.' + +`TAGS' + Update a tags table for this program. + +`info' + Generate any Info files needed. The best way to write the rules + is as follows: + + info: foo.info + + foo.info: foo.texi chap1.texi chap2.texi + $(MAKEINFO) $(srcdir)/foo.texi + + You must define the variable `MAKEINFO' in the Makefile. It should + run the `makeinfo' program, which is part of the Texinfo + distribution. + + Normally a GNU distribution comes with Info files, and that means + the Info files are present in the source directory. Therefore, + the Make rule for an info file should update it in the source + directory. When users build the package, ordinarily Make will not + update the Info files because they will already be up to date. + +`dvi' + Generate DVI files for all Texinfo documentation. For example: + + dvi: foo.dvi + + foo.dvi: foo.texi chap1.texi chap2.texi + $(TEXI2DVI) $(srcdir)/foo.texi + + You must define the variable `TEXI2DVI' in the Makefile. It should + run the program `texi2dvi', which is part of the Texinfo + distribution.(1) Alternatively, write just the dependencies, and + allow GNU `make' to provide the command. + +`dist' + Create a distribution tar file for this program. The tar file + should be set up so that the file names in the tar file start with + a subdirectory name which is the name of the package it is a + distribution for. This name can include the version number. + + For example, the distribution tar file of GCC version 1.40 unpacks + into a subdirectory named `gcc-1.40'. + + The easiest way to do this is to create a subdirectory + appropriately named, use `ln' or `cp' to install the proper files + in it, and then `tar' that subdirectory. + + Compress the tar file file with `gzip'. For example, the actual + distribution file for GCC version 1.40 is called `gcc-1.40.tar.gz'. + + The `dist' target should explicitly depend on all non-source files + that are in the distribution, to make sure they are up to date in + the distribution. *Note Making Releases: Releases. + +`check' + Perform self-tests (if any). The user must build the program + before running the tests, but need not install the program; you + should write the self-tests so that they work when the program is + built but not installed. + + The following targets are suggested as conventional names, for +programs in which they are useful. + +`installcheck' + Perform installation tests (if any). The user must build and + install the program before running the tests. You should not + assume that `$(bindir)' is in the search path. + +`installdirs' + It's useful to add a target named `installdirs' to create the + directories where files are installed, and their parent + directories. There is a script called `mkinstalldirs' which is + convenient for this; you can find it in the Texinfo package. You + can use a rule like this: + + # Make sure all installation directories (e.g. $(bindir)) + # actually exist by making them if necessary. + installdirs: mkinstalldirs + $(srcdir)/mkinstalldirs $(bindir) $(datadir) \ + $(libdir) $(infodir) \ + $(mandir) + + This rule should not modify the directories where compilation is + done. It should do nothing but create installation directories. + + ---------- Footnotes ---------- + + (1) `texi2dvi' uses TeX to do the real work of formatting. TeX is +not distributed with Texinfo. + + +File: standards.info, Node: Install Command Categories, Prev: Standard Targets, Up: Makefile Conventions + +Install Command Categories +-------------------------- + + When writing the `install' target, you must classify all the +commands into three categories: normal ones, "pre-installation" +commands and "post-installation" commands. + + Normal commands move files into their proper places, and set their +modes. They may not alter any files except the ones that come entirely +from the package they belong to. + + Pre-installation and post-installation commands may alter other +files; in particular, they can edit global configuration files or data +bases. + + Pre-installation commands are typically executed before the normal +commands, and post-installation commands are typically run after the +normal commands. + + The most common use for a post-installation command is to run +`install-info'. This cannot be done with a normal command, since it +alters a file (the Info directory) which does not come entirely and +solely from the package being installed. It is a post-installation +command because it needs to be done after the normal command which +installs the package's Info files. + + Most programs don't need any pre-installation commands, but we have +the feature just in case it is needed. + + To classify the commands in the `install' rule into these three +categories, insert "category lines" among them. A category line +specifies the category for the commands that follow. + + A category line consists of a tab and a reference to a special Make +variable, plus an optional comment at the end. There are three +variables you can use, one for each category; the variable name +specifies the category. Category lines are no-ops in ordinary execution +because these three Make variables are normally undefined (and you +*should not* define them in the makefile). + + Here are the three possible category lines, each with a comment that +explains what it means: + + $(PRE_INSTALL) # Pre-install commands follow. + $(POST_INSTALL) # Post-install commands follow. + $(NORMAL_INSTALL) # Normal commands follow. + + If you don't use a category line at the beginning of the `install' +rule, all the commands are classified as normal until the first category +line. If you don't use any category lines, all the commands are +classified as normal. + + These are the category lines for `uninstall': + + $(PRE_UNINSTALL) # Pre-uninstall commands follow. + $(POST_UNINSTALL) # Post-uninstall commands follow. + $(NORMAL_UNINSTALL) # Normal commands follow. + + Typically, a pre-uninstall command would be used for deleting entries +from the Info directory. + + If the `install' or `uninstall' target has any dependencies which +act as subroutines of installation, then you should start *each* +dependency's commands with a category line, and start the main target's +commands with a category line also. This way, you can ensure that each +command is placed in the right category regardless of which of the +dependencies actually run. + + Pre-installation and post-installation commands should not run any +programs except for these: + + [ basename bash cat chgrp chmod chown cmp cp dd diff echo + egrep expand expr false fgrep find getopt grep gunzip gzip + hostname install install-info kill ldconfig ln ls md5sum + mkdir mkfifo mknod mv printenv pwd rm rmdir sed sort tee + test touch true uname xargs yes + + The reason for distinguishing the commands in this way is for the +sake of making binary packages. Typically a binary package contains +all the executables and other files that need to be installed, and has +its own method of installing them--so it does not need to run the normal +installation commands. But installing the binary package does need to +execute the pre-installation and post-installation commands. + + Programs to build binary packages work by extracting the +pre-installation and post-installation commands. Here is one way of +extracting the pre-installation commands: + + make -n install -o all \ + PRE_INSTALL=pre-install \ + POST_INSTALL=post-install \ + NORMAL_INSTALL=normal-install \ + | gawk -f pre-install.awk + +where the file `pre-install.awk' could contain this: + + $0 ~ /^\t[ \t]*(normal_install|post_install)[ \t]*$/ {on = 0} + on {print $0} + $0 ~ /^\t[ \t]*pre_install[ \t]*$/ {on = 1} + + The resulting file of pre-installation commands is executed as a +shell script as part of installing the binary package. + + +File: standards.info, Node: Releases, Prev: Makefile Conventions, Up: Managing Releases + +Making Releases +=============== + + Package the distribution of `Foo version 69.96' up in a gzipped tar +file with the name `foo-69.96.tar.gz'. It should unpack into a +subdirectory named `foo-69.96'. + + Building and installing the program should never modify any of the +files contained in the distribution. This means that all the files +that form part of the program in any way must be classified into "source +files" and "non-source files". Source files are written by humans and +never changed automatically; non-source files are produced from source +files by programs under the control of the Makefile. + + Naturally, all the source files must be in the distribution. It is +okay to include non-source files in the distribution, provided they are +up-to-date and machine-independent, so that building the distribution +normally will never modify them. We commonly include non-source files +produced by Bison, `lex', TeX, and `makeinfo'; this helps avoid +unnecessary dependencies between our distributions, so that users can +install whichever packages they want to install. + + Non-source files that might actually be modified by building and +installing the program should *never* be included in the distribution. +So if you do distribute non-source files, always make sure they are up +to date when you make a new distribution. + + Make sure that the directory into which the distribution unpacks (as +well as any subdirectories) are all world-writable (octal mode 777). +This is so that old versions of `tar' which preserve the ownership and +permissions of the files from the tar archive will be able to extract +all the files even if the user is unprivileged. + + Make sure that all the files in the distribution are world-readable. + + Make sure that no file name in the distribution is more than 14 +characters long. Likewise, no file created by building the program +should have a name longer than 14 characters. The reason for this is +that some systems adhere to a foolish interpretation of the POSIX +standard, and refuse to open a longer name, rather than truncating as +they did in the past. + + Don't include any symbolic links in the distribution itself. If the +tar file contains symbolic links, then people cannot even unpack it on +systems that don't support symbolic links. Also, don't use multiple +names for one file in different directories, because certain file +systems cannot handle this and that prevents unpacking the distribution. + + Try to make sure that all the file names will be unique on MS-DOS. A +name on MS-DOS consists of up to 8 characters, optionally followed by a +period and up to three characters. MS-DOS will truncate extra +characters both before and after the period. Thus, `foobarhacker.c' +and `foobarhacker.o' are not ambiguous; they are truncated to +`foobarha.c' and `foobarha.o', which are distinct. + + Include in your distribution a copy of the `texinfo.tex' you used to +test print any `*.texinfo' or `*.texi' files. + + Likewise, if your program uses small GNU software packages like +regex, getopt, obstack, or termcap, include them in the distribution +file. Leaving them out would make the distribution file a little +smaller at the expense of possible inconvenience to a user who doesn't +know what other files to get. + + + +Tag Table: +Node: Top1010 +Node: Preface1554 +Node: Intellectual Property2582 +Node: Reading Non-Free Code2957 +Node: Contributions4689 +Node: Design Advice6683 +Node: Compatibility7200 +Node: Using Extensions8711 +Node: ANSI C10213 +Node: Source Language11449 +Node: Program Behavior12942 +Node: Semantics13651 +Node: Libraries17801 +Node: Errors19036 +Node: User Interfaces20259 +Node: Option Table27131 +Node: Memory Usage41686 +Node: Writing C42680 +Node: Formatting43519 +Node: Comments46791 +Node: Syntactic Conventions50089 +Node: Names53027 +Node: System Portability54763 +Node: CPU Portability56539 +Node: System Functions58700 +Node: Internationalization63804 +Node: Mmap66952 +Node: Documentation67657 +Node: GNU Manuals68215 +Node: Manual Structure Details72102 +Node: NEWS File73432 +Node: Change Logs74113 +Node: Change Log Concepts74830 +Node: Style of Change Logs76598 +Node: Simple Changes78152 +Node: Conditional Changes79343 +Node: Man Pages80720 +Node: Reading other Manuals82339 +Node: Managing Releases83123 +Node: Configuration83859 +Node: Makefile Conventions90799 +Node: Makefile Basics91479 +Node: Utilities in Makefiles94648 +Node: Command Variables96784 +Node: Directory Variables99812 +Node: Standard Targets110394 +Node: Install Command Categories120895 +Node: Releases125468 + +End Tag Table |