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This is Info file ../info/standards.info, produced by Makeinfo version 1.68 from the input file 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 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: 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. * 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, 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, avoid writing code that makes assumptions about the structure of words. Don't construct words from parts. Here is an example of what not to do: prinf ("%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, prinf (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: prinf ((nfiles > 1 ? "%d files processed" : "%d file processed"), nfiles); This way, you can apply gettext to each of the two strings independently: prinf ((nfiles > 1 ? gettext ("%d files processed") : gettext ("%d file processed")), nfiles); This can handle any language, no matter how it forms the plural of the word for "file." 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'). The manual 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 goals that a user will have in mind, and explain how to accomplish them. 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; they are a bad example to follow. 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. 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 program to which the manual applies. 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. The manual should have a node named `PROGRAM Invocation' or `Invoking PROGRAM', where PROGRAM stands for the name of the program being described, as you would type it in the shell to run the 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 eliminate conceptual inconsistencies between different parts of a program; they can give you a history of how the conflicting concepts arose. A 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. 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. Separate unrelated 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. Here are some examples: * 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 the entry. There's no need to describe the full purpose of the changes or how they work together. It is better to put such explanations in comments in the code. That's why just "New function" is enough; there is a comment with the function in the source to explain what it does. However, sometimes it is useful to write one line to describe the overall purpose of a large batch of changes. 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. 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. Just write in the entry for the function being called, "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. Write just, "Doc fix." 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 the passage with the way the program actually works. 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 `x', `x-toolkit', `gnu-as' (or `gas'), `gnu-ld', `gnu-libc', and `gdb'. 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 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 `$(srcdir)/' if the file is an unchanging part of the source code. Without one of these prefixes, the current search path is used. The distinction between `./' and `$(srcdir)/' is important when 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 current directory is not the source directory, because `foo.man' and `sedscript' are not in the current 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 > $@ 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 echo egrep expr false grep ln mkdir mv pwd rm rmdir sed test touch true 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 lex make makeinfo ranlib texi2dvi yacc Use the following `make' variables: $(AR) $(BISON) $(CC) $(FLEX) $(INSTALL) $(LD) $(LEX) $(MAKE) $(MAKEINFO) $(RANLIB) $(TEXI2DVI) $(YACC) When you use `ranlib', you should make sure nothing bad happens if the system does not have `ranlib'. Arrange to ignore an error from that command, and print a message before the command to tell the user that failure of the `ranlib' command does not mean a problem. (The Autoconf `AC_PROG_RANLIB' macro can help with this.) If you use symbolic links, you should implement a fallback for systems that don't have symbolic links. It is ok to use other utilities in Makefile portions (or scripts) intended only for particular systems where you know those utilities exist. File: standards.info, Node: Command Variables, Next: Directory Variables, Prev: Utilities in Makefiles, Up: Makefile Conventions Variables for Specifying Commands --------------------------------- Makefiles should provide variables for overriding certain commands, options, and so on. In particular, you should run most utility programs via variables. Thus, if you use Bison, have a variable named `BISON' whose default value is set with `BISON = bison', and refer to it with `$(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 name `CFLAGS' is an exception to this rule, but we keep it because it is 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) $< Do include the `-g' option in `CFLAGS', because that is not *required* for proper compilation. You can consider it a default that is only recommended. If the package is set up so that it is compiled with GCC by default, then you might as well include `-O' in the default value of `CFLAGS' as well. Put `CFLAGS' last in the compilation command, after other variables containing compiler options, so the user can use `CFLAGS' to override the others. Every Makefile should define the variable `INSTALL', which is the basic command for installing a file into the system. Every Makefile should also define the variables `INSTALL_PROGRAM' and `INSTALL_DATA'. (The default for each of these should be `$(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 `$(prefix)/etc'. (If you are using Autoconf, write it as `@sysconfdir@'.) Do not install executables in this directory (they probably belong in `$(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@'.) `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 `$(prefix)/include'. (If you are using Autoconf, write it as `@includedir@'.) Most compilers other than GCC do not look for header files in `/usr/local/include'. So installing the header files this way is only useful with GCC. Sometimes this is not a problem because some libraries are only really intended to work with GCC. But some libraries are intended to work with other compilers. They should install their header files in two places, one specified by `includedir' and one specified by `oldincludedir'. `oldincludedir' The directory for installing `#include' header files for use with compilers other than GCC. This should normally be `/usr/include'. (If you are using Autoconf, you can write it as `@oldincludedir@'.) The Makefile commands should check whether the value of `oldincludedir' is empty. If it is, they should not try to use it; they should cancel the second installation of the header files. A package should not replace an existing header in this directory unless the header came from the same package. Thus, if your Foo package provides a header file `foo.h', then it should install the header file in the `oldincludedir' directory if either (1) there is no `foo.h' there or (2) the `foo.h' that exists came from the Foo package. To tell whether `foo.h' came from the Foo package, put a magic string in the file--part of a comment--and `grep' for that string. Unix-style man pages are installed in one of the following: `mandir' The top-level directory for installing the man pages (if any) for this package. It will normally be `/usr/local/man', but you should write it as `$(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.