with a rule for the special target `.SUFFIXES', but that does not alter this variable.  File: make.info, Node: Implicit Rule Search, Prev: Suffix Rules, Up: Implicit Rules 10.8 Implicit Rule Search Algorithm =================================== Here is the procedure `make' uses for searching for an implicit rule for a target T. This procedure is followed for each double-colon rule with no commands, for each target of ordinary rules none of which have commands, and for each prerequisite that is not the target of any rule. It is also followed recursively for prerequisites that come from implicit rules, in the search for a chain of rules. Suffix rules are not mentioned in this algorithm because suffix rules are converted to equivalent pattern rules once the makefiles have been read in. For an archive member target of the form `ARCHIVE(MEMBER)', the following algorithm is run twice, first using the entire target name T, and second using `(MEMBER)' as the target T if the first run found no rule. 1. Split T into a directory part, called D, and the rest, called N. For example, if T is `src/foo.o', then D is `src/' and N is `foo.o'. 2. Make a list of all the pattern rules one of whose targets matches T or N. If the target pattern contains a slash, it is matched against T; otherwise, against N. 3. If any rule in that list is _not_ a match-anything rule, then remove all nonterminal match-anything rules from the list. 4. Remove from the list all rules with no commands. 5. For each pattern rule in the list: a. Find the stem S, which is the nonempty part of T or N matched by the `%' in the target pattern. b. Compute the prerequisite names by substituting S for `%'; if the target pattern does not contain a slash, append D to the front of each prerequisite name. c. Test whether all the prerequisites exist or ought to exist. (If a file name is mentioned in the makefile as a target or as an explicit prerequisite, then we say it ought to exist.) If all prerequisites exist or ought to exist, or there are no prerequisites, then this rule applies. 6. If no pattern rule has been found so far, try harder. For each pattern rule in the list: a. If the rule is terminal, ignore it and go on to the next rule. b. Compute the prerequisite names as before. c. Test whether all the prerequisites exist or ought to exist. d. For each prerequisite that does not exist, follow this algorithm recursively to see if the prerequisite can be made by an implicit rule. e. If all prerequisites exist, ought to exist, or can be made by implicit rules, then this rule applies. 7. If no implicit rule applies, the rule for `.DEFAULT', if any, applies. In that case, give T the same commands that `.DEFAULT' has. Otherwise, there are no commands for T. Once a rule that applies has been found, for each target pattern of the rule other than the one that matched T or N, the `%' in the pattern is replaced with S and the resultant file name is stored until the commands to remake the target file T are executed. After these commands are executed, each of these stored file names are entered into the data base and marked as having been updated and having the same update status as the file T. When the commands of a pattern rule are executed for T, the automatic variables are set corresponding to the target and prerequisites. *Note Automatic Variables::.  File: make.info, Node: Archives, Next: Features, Prev: Implicit Rules, Up: Top 11 Using `make' to Update Archive Files *************************************** "Archive files" are files containing named subfiles called "members"; they are maintained with the program `ar' and their main use is as subroutine libraries for linking. * Menu: * Archive Members:: Archive members as targets. * Archive Update:: The implicit rule for archive member targets. * Archive Pitfalls:: Dangers to watch out for when using archives. * Archive Suffix Rules:: You can write a special kind of suffix rule for updating archives.  File: make.info, Node: Archive Members, Next: Archive Update, Prev: Archives, Up: Archives 11.1 Archive Members as Targets =============================== An individual member of an archive file can be used as a target or prerequisite in `make'. You specify the member named MEMBER in archive file ARCHIVE as follows: ARCHIVE(MEMBER) This construct is available only in targets and prerequisites, not in commands! Most programs that you might use in commands do not support this syntax and cannot act directly on archive members. Only `ar' and other programs specifically designed to operate on archives can do so. Therefore, valid commands to update an archive member target probably must use `ar'. For example, this rule says to create a member `hack.o' in archive `foolib' by copying the file `hack.o': foolib(hack.o) : hack.o ar cr foolib hack.o In fact, nearly all archive member targets are updated in just this way and there is an implicit rule to do it for you. *Please note:* The `c' flag to `ar' is required if the archive file does not already exist. To specify several members in the same archive, you can write all the member names together between the parentheses. For example: foolib(hack.o kludge.o) is equivalent to: foolib(hack.o) foolib(kludge.o) You can also use shell-style wildcards in an archive member reference. *Note Using Wildcard Characters in File Names: Wildcards. For example, `foolib(*.o)' expands to all existing members of the `foolib' archive whose names end in `.o'; perhaps `foolib(hack.o) foolib(kludge.o)'.  File: make.info, Node: Archive Update, Next: Archive Pitfalls, Prev: Archive Members, Up: Archives 11.2 Implicit Rule for Archive Member Targets ============================================= Recall that a target that looks like `A(M)' stands for the member named M in the archive file A. When `make' looks for an implicit rule for such a target, as a special feature it considers implicit rules that match `(M)', as well as those that match the actual target `A(M)'. This causes one special rule whose target is `(%)' to match. This rule updates the target `A(M)' by copying the file M into the archive. For example, it will update the archive member target `foo.a(bar.o)' by copying the _file_ `bar.o' into the archive `foo.a' as a _member_ named `bar.o'. When this rule is chained with others, the result is very powerful. Thus, `make "foo.a(bar.o)"' (the quotes are needed to protect the `(' and `)' from being interpreted specially by the shell) in the presence of a file `bar.c' is enough to cause the following commands to be run, even without a makefile: cc -c bar.c -o bar.o ar r foo.a bar.o rm -f bar.o Here `make' has envisioned the file `bar.o' as an intermediate file. *Note Chains of Implicit Rules: Chained Rules. Implicit rules such as this one are written using the automatic variable `$%'. *Note Automatic Variables::. An archive member name in an archive cannot contain a directory name, but it may be useful in a makefile to pretend that it does. If you write an archive member target `foo.a(dir/file.o)', `make' will perform automatic updating with this command: ar r foo.a dir/file.o which has the effect of copying the file `dir/file.o' into a member named `file.o'. In connection with such usage, the automatic variables `%D' and `%F' may be useful. * Menu: * Archive Symbols:: How to update archive symbol directories.  File: make.info, Node: Archive Symbols, Prev: Archive Update, Up: Archive Update 11.2.1 Updating Archive Symbol Directories ------------------------------------------ An archive file that is used as a library usually contains a special member named `__.SYMDEF' that contains a directory of the external symbol names defined by all the other members. After you update any other members, you need to update `__.SYMDEF' so that it will summarize the other members properly. This is done by running the `ranlib' program: ranlib ARCHIVEFILE Normally you would put this command in the rule for the archive file, and make all the members of the archive file prerequisites of that rule. For example, libfoo.a: libfoo.a(x.o) libfoo.a(y.o) ... ranlib libfoo.a The effect of this is to update archive members `x.o', `y.o', etc., and then update the symbol directory member `__.SYMDEF' by running `ranlib'. The rules for updating the members are not shown here; most likely you can omit them and use the implicit rule which copies files into the archive, as described in the preceding section. This is not necessary when using the GNU `ar' program, which updates the `__.SYMDEF' member automatically.  File: make.info, Node: Archive Pitfalls, Next: Archive Suffix Rules, Prev: Archive Update, Up: Archives 11.3 Dangers When Using Archives ================================ It is important to be careful when using parallel execution (the `-j' switch; *note Parallel Execution: Parallel.) and archives. If multiple `ar' commands run at the same time on the same archive file, they will not know about each other and can corrupt the file. Possibly a future version of `make' will provide a mechanism to circumvent this problem by serializing all commands that operate on the same archive file. But for the time being, you must either write your makefiles to avoid this problem in some other way, or not use `-j'.  File: make.info, Node: Archive Suffix Rules, Prev: Archive Pitfalls, Up: Archives 11.4 Suffix Rules for Archive Files =================================== You can write a special kind of suffix rule for dealing with archive files. *Note Suffix Rules::, for a full explanation of suffix rules. Archive suffix rules are obsolete in GNU `make', because pattern rules for archives are a more general mechanism (*note Archive Update::). But they are retained for compatibility with other `make's. To write a suffix rule for archives, you simply write a suffix rule using the target suffix `.a' (the usual suffix for archive files). For example, here is the old-fashioned suffix rule to update a library archive from C source files: .c.a: $(CC) $(CFLAGS) $(CPPFLAGS) -c $< -o $*.o $(AR) r $@ $*.o $(RM) $*.o This works just as if you had written the pattern rule: (%.o): %.c $(CC) $(CFLAGS) $(CPPFLAGS) -c $< -o $*.o $(AR) r $@ $*.o $(RM) $*.o In fact, this is just what `make' does when it sees a suffix rule with `.a' as the target suffix. Any double-suffix rule `.X.a' is converted to a pattern rule with the target pattern `(%.o)' and a prerequisite pattern of `%.X'. Since you might want to use `.a' as the suffix for some other kind of file, `make' also converts archive suffix rules to pattern rules in the normal way (*note Suffix Rules::). Thus a double-suffix rule `.X.a' produces two pattern rules: `(%.o): %.X' and `%.a: %.X'.  File: make.info, Node: Features, Next: Missing, Prev: Archives, Up: Top 12 Features of GNU `make' ************************* Here is a summary of the features of GNU `make', for comparison with and credit to other versions of `make'. We consider the features of `make' in 4.2 BSD systems as a baseline. If you are concerned with writing portable makefiles, you should not use the features of `make' listed here, nor the ones in *Note Missing::. Many features come from the version of `make' in System V. * The `VPATH' variable and its special meaning. *Note Searching Directories for Prerequisites: Directory Search. This feature exists in System V `make', but is undocumented. It is documented in 4.3 BSD `make' (which says it mimics System V's `VPATH' feature). * Included makefiles. *Note Including Other Makefiles: Include. Allowing multiple files to be included with a single directive is a GNU extension. * Variables are read from and communicated via the environment. *Note Variables from the Environment: Environment. * Options passed through the variable `MAKEFLAGS' to recursive invocations of `make'. *Note Communicating Options to a Sub-`make': Options/Recursion. * The automatic variable `$%' is set to the member name in an archive reference. *Note Automatic Variables::. * The automatic variables `$@', `$*', `$<', `$%', and `$?' have corresponding forms like `$(@F)' and `$(@D)'. We have generalized this to `$^' as an obvious extension. *Note Automatic Variables::. * Substitution variable references. *Note Basics of Variable References: Reference. * The command-line options `-b' and `-m', accepted and ignored. In System V `make', these options actually do something. * Execution of recursive commands to run `make' via the variable `MAKE' even if `-n', `-q' or `-t' is specified. *Note Recursive Use of `make': Recursion. * Support for suffix `.a' in suffix rules. *Note Archive Suffix Rules::. This feature is obsolete in GNU `make', because the general feature of rule chaining (*note Chains of Implicit Rules: Chained Rules.) allows one pattern rule for installing members in an archive (*note Archive Update::) to be sufficient. * The arrangement of lines and backslash-newline combinations in commands is retained when the commands are printed, so they appear as they do in the makefile, except for the stripping of initial whitespace. The following features were inspired by various other versions of `make'. In some cases it is unclear exactly which versions inspired which others. * Pattern rules using `%'. This has been implemented in several versions of `make'. We're not sure who invented it first, but it's been spread around a bit. *Note Defining and Redefining Pattern Rules: Pattern Rules. * Rule chaining and implicit intermediate files. This was implemented by Stu Feldman in his version of `make' for AT&T Eighth Edition Research Unix, and later by Andrew Hume of AT&T Bell Labs in his `mk' program (where he terms it "transitive closure"). We do not really know if we got this from either of them or thought it up ourselves at the same time. *Note Chains of Implicit Rules: Chained Rules. * The automatic variable `$^' containing a list of all prerequisites of the current target. We did not invent this, but we have no idea who did. *Note Automatic Variables::. The automatic variable `$+' is a simple extension of `$^'. * The "what if" flag (`-W' in GNU `make') was (as far as we know) invented by Andrew Hume in `mk'. *Note Instead of Executing the Commands: Instead of Execution. * The concept of doing several things at once (parallelism) exists in many incarnations of `make' and similar programs, though not in the System V or BSD implementations. *Note Command Execution: Execution. * Modified variable references using pattern substitution come from SunOS 4. *Note Basics of Variable References: Reference. This functionality was provided in GNU `make' by the `patsubst' function before the alternate syntax was implemented for compatibility with SunOS 4. It is not altogether clear who inspired whom, since GNU `make' had `patsubst' before SunOS 4 was released. * The special significance of `+' characters preceding command lines (*note Instead of Executing the Commands: Instead of Execution.) is mandated by `IEEE Standard 1003.2-1992' (POSIX.2). * The `+=' syntax to append to the value of a variable comes from SunOS 4 `make'. *Note Appending More Text to Variables: Appending. * The syntax `ARCHIVE(MEM1 MEM2...)' to list multiple members in a single archive file comes from SunOS 4 `make'. *Note Archive Members::. * The `-include' directive to include makefiles with no error for a nonexistent file comes from SunOS 4 `make'. (But note that SunOS 4 `make' does not allow multiple makefiles to be specified in one `-include' directive.) The same feature appears with the name `sinclude' in SGI `make' and perhaps others. The remaining features are inventions new in GNU `make': * Use the `-v' or `--version' option to print version and copyright information. * Use the `-h' or `--help' option to summarize the options to `make'. * Simply-expanded variables. *Note The Two Flavors of Variables: Flavors. * Pass command-line variable assignments automatically through the variable `MAKE' to recursive `make' invocations. *Note Recursive Use of `make': Recursion. * Use the `-C' or `--directory' command option to change directory. *Note Summary of Options: Options Summary. * Make verbatim variable definitions with `define'. *Note Defining Variables Verbatim: Defining. * Declare phony targets with the special target `.PHONY'. Andrew Hume of AT&T Bell Labs implemented a similar feature with a different syntax in his `mk' program. This seems to be a case of parallel discovery. *Note Phony Targets: Phony Targets. * Manipulate text by calling functions. *Note Functions for Transforming Text: Functions. * Use the `-o' or `--old-file' option to pretend a file's modification-time is old. *Note Avoiding Recompilation of Some Files: Avoiding Compilation. * Conditional execution. This feature has been implemented numerous times in various versions of `make'; it seems a natural extension derived from the features of the C preprocessor and similar macro languages and is not a revolutionary concept. *Note Conditional Parts of Makefiles: Conditionals. * Specify a search path for included makefiles. *Note Including Other Makefiles: Include. * Specify extra makefiles to read with an environment variable. *Note The Variable `MAKEFILES': MAKEFILES Variable. * Strip leading sequences of `./' from file names, so that `./FILE' and `FILE' are considered to be the same file. * Use a special search method for library prerequisites written in the form `-lNAME'. *Note Directory Search for Link Libraries: Libraries/Search. * Allow suffixes for suffix rules (*note Old-Fashioned Suffix Rules: Suffix Rules.) to contain any characters. In other versions of `make', they must begin with `.' and not contain any `/' characters. * Keep track of the current level of `make' recursion using the variable `MAKELEVEL'. *Note Recursive Use of `make': Recursion. * Provide any goals given on the command line in the variable `MAKECMDGOALS'. *Note Arguments to Specify the Goals: Goals. * Specify static pattern rules. *Note Static Pattern Rules: Static Pattern. * Provide selective `vpath' search. *Note Searching Directories for Prerequisites: Directory Search. * Provide computed variable references. *Note Basics of Variable References: Reference. * Update makefiles. *Note How Makefiles Are Remade: Remaking Makefiles. System V `make' has a very, very limited form of this functionality in that it will check out SCCS files for makefiles. * Various new built-in implicit rules. *Note Catalogue of Implicit Rules: Catalogue of Rules. * The built-in variable `MAKE_VERSION' gives the version number of `make'.  File: make.info, Node: Missing, Next: Makefile Conventions, Prev: Features, Up: Top 13 Incompatibilities and Missing Features ***************************************** The `make' programs in various other systems support a few features that are not implemented in GNU `make'. The POSIX.2 standard (`IEEE Standard 1003.2-1992') which specifies `make' does not require any of these features. * A target of the form `FILE((ENTRY))' stands for a member of archive file FILE. The member is chosen, not by name, but by being an object file which defines the linker symbol ENTRY. This feature was not put into GNU `make' because of the nonmodularity of putting knowledge into `make' of the internal format of archive file symbol tables. *Note Updating Archive Symbol Directories: Archive Symbols. * Suffixes (used in suffix rules) that end with the character `~' have a special meaning to System V `make'; they refer to the SCCS file that corresponds to the file one would get without the `~'. For example, the suffix rule `.c~.o' would make the file `N.o' from the SCCS file `s.N.c'. For complete coverage, a whole series of such suffix rules is required. *Note Old-Fashioned Suffix Rules: Suffix Rules. In GNU `make', this entire series of cases is handled by two pattern rules for extraction from SCCS, in combination with the general feature of rule chaining. *Note Chains of Implicit Rules: Chained Rules. * In System V and 4.3 BSD `make', files found by `VPATH' search (*note Searching Directories for Prerequisites: Directory Search.) have their names changed inside command strings. We feel it is much cleaner to always use automatic variables and thus make this feature obsolete. * In some Unix `make's, the automatic variable `$*' appearing in the prerequisites of a rule has the amazingly strange "feature" of expanding to the full name of the _target of that rule_. We cannot imagine what went on in the minds of Unix `make' developers to do this; it is utterly inconsistent with the normal definition of `$*'. * In some Unix `make's, implicit rule search (*note Using Implicit Rules: Implicit Rules.) is apparently done for _all_ targets, not just those without commands. This means you can do: foo.o: cc -c foo.c and Unix `make' will intuit that `foo.o' depends on `foo.c'. We feel that such usage is broken. The prerequisite properties of `make' are well-defined (for GNU `make', at least), and doing such a thing simply does not fit the model. * GNU `make' does not include any built-in implicit rules for compiling or preprocessing EFL programs. If we hear of anyone who is using EFL, we will gladly add them. * It appears that in SVR4 `make', a suffix rule can be specified with no commands, and it is treated as if it had empty commands (*note Empty Commands::). For example: .c.a: will override the built-in `.c.a' suffix rule. We feel that it is cleaner for a rule without commands to always simply add to the prerequisite list for the target. The above example can be easily rewritten to get the desired behavior in GNU `make': .c.a: ; * Some versions of `make' invoke the shell with the `-e' flag, except under `-k' (*note Testing the Compilation of a Program: Testing.). The `-e' flag tells the shell to exit as soon as any program it runs returns a nonzero status. We feel it is cleaner to write each shell command line to stand on its own and not require this special treatment.  File: make.info, Node: Makefile Conventions, Next: Quick Reference, Prev: Missing, Up: Top 14 Makefile Conventions *********************** This node describes conventions for writing the Makefiles for GNU programs. Using Automake will help you write a Makefile that follows these conventions. * Menu: * Makefile Basics:: General Conventions for Makefiles * Utilities in Makefiles:: Utilities in Makefiles * Command Variables:: Variables for Specifying Commands * Directory Variables:: Variables for Installation Directories * Standard Targets:: Standard Targets for Users * Install Command Categories:: Three categories of commands in the `install' rule: normal, pre-install and post-install.  File: make.info, Node: Makefile Basics, Next: Utilities in Makefiles, Up: Makefile Conventions 14.1 General Conventions for Makefiles ====================================== Every Makefile should contain this line: SHELL = /bin/sh to avoid trouble on systems where the `SHELL' variable might be inherited from the environment. (This is never a problem with GNU `make'.) Different `make' programs have incompatible suffix lists and implicit rules, and this sometimes creates confusion or misbehavior. So it is a good idea to set the suffix list explicitly using only the suffixes you need in the particular Makefile, like this: .SUFFIXES: .SUFFIXES: .c .o The first line clears out the suffix list, the second introduces all suffixes which may be subject to implicit rules in this Makefile. Don't assume that `.' is in the path for command execution. When you need to run programs that are a part of your package during the make, please make sure that it uses `./' if the program is built as part of the make or `$(srcdir)/' if the file is an unchanging part of the source code. Without one of these prefixes, the current search path is used. The distinction between `./' (the "build directory") and `$(srcdir)/' (the "source directory") is important because users can build in a separate directory using the `--srcdir' option to `configure'. A rule of the form: foo.1 : foo.man sedscript sed -e sedscript foo.man > foo.1 will fail when the build directory is not the source directory, because `foo.man' and `sedscript' are in the source directory. When using GNU `make', relying on `VPATH' to find the source file will work in the case where there is a single dependency file, since the `make' automatic variable `$<' will represent the source file wherever it is. (Many versions of `make' set `$<' only in implicit rules.) A Makefile target like foo.o : bar.c $(CC) -I. -I$(srcdir) $(CFLAGS) -c bar.c -o foo.o should instead be written as foo.o : bar.c $(CC) -I. -I$(srcdir) $(CFLAGS) -c $< -o $@ in order to allow `VPATH' to work correctly. When the target has multiple dependencies, using an explicit `$(srcdir)' is the easiest way to make the rule work well. For example, the target above for `foo.1' is best written as: foo.1 : foo.man sedscript sed -e $(srcdir)/sedscript $(srcdir)/foo.man > $@ GNU distributions usually contain some files which are not source files--for example, Info files, and the output from Autoconf, Automake, Bison or Flex. Since these files normally appear in the source directory, they should always appear in the source directory, not in the build directory. So Makefile rules to update them should put the updated files in the source directory. However, if a file does not appear in the distribution, then the Makefile should not put it in the source directory, because building a program in ordinary circumstances should not modify the source directory in any way. Try to make the build and installation targets, at least (and all their subtargets) work correctly with a parallel `make'.  File: make.info, Node: Utilities in Makefiles, Next: Command Variables, Prev: Makefile Basics, Up: Makefile Conventions 14.2 Utilities in Makefiles =========================== Write the Makefile commands (and any shell scripts, such as `configure') to run in `sh', not in `csh'. Don't use any special features of `ksh' or `bash'. The `configure' script and the Makefile rules for building and installation should not use any utilities directly except these: cat cmp cp diff echo egrep expr false grep install-info ln ls mkdir mv pwd rm rmdir sed sleep sort tar test touch true The compression program `gzip' can be used in the `dist' rule. Stick to the generally supported options for these programs. For example, don't use `mkdir -p', convenient as it may be, because most systems don't support it. It is a good idea to avoid creating symbolic links in makefiles, since a few systems don't support them. The Makefile rules for building and installation can also use compilers and related programs, but should do so via `make' variables so that the user can substitute alternatives. Here are some of the programs we mean: ar bison cc flex install ld ldconfig lex make makeinfo ranlib texi2dvi yacc Use the following `make' variables to run those programs: $(AR) $(BISON) $(CC) $(FLEX) $(INSTALL) $(LD) $(LDCONFIG) $(LEX) $(MAKE) $(MAKEINFO) $(RANLIB) $(TEXI2DVI) $(YACC) When you use `ranlib' or `ldconfig', you should make sure nothing bad happens if the system does not have the program in question. Arrange to ignore an error from that command, and print a message before the command to tell the user that failure of this command does not mean a problem. (The Autoconf `AC_PROG_RANLIB' macro can help with this.) If you use symbolic links, you should implement a fallback for systems that don't have symbolic links. Additional utilities that can be used via Make variables are: chgrp chmod chown mknod It is ok to use other utilities in Makefile portions (or scripts) intended only for particular systems where you know those utilities exist.  File: make.info, Node: Command Variables, Next: Directory Variables, Prev: Utilities in Makefiles, Up: Makefile Conventions 14.3 Variables for Specifying Commands ====================================== Makefiles should provide variables for overriding certain commands, options, and so on. In particular, you should run most utility programs via variables. Thus, if you use Bison, have a variable named `BISON' whose default value is set with `BISON = bison', and refer to it with `$(BISON)' whenever you need to use Bison. File management utilities such as `ln', `rm', `mv', and so on, need not be referred to through variables in this way, since users don't need to replace them with other programs. Each program-name variable should come with an options variable that is used to supply options to the program. Append `FLAGS' to the program-name variable name to get the options variable name--for example, `BISONFLAGS'. (The names `CFLAGS' for the C compiler, `YFLAGS' for yacc, and `LFLAGS' for lex, are exceptions to this rule, but we keep them because they are standard.) Use `CPPFLAGS' in any compilation command that runs the preprocessor, and use `LDFLAGS' in any compilation command that does linking as well as in any direct use of `ld'. If there are C compiler options that _must_ be used for proper compilation of certain files, do not include them in `CFLAGS'. Users expect to be able to specify `CFLAGS' freely themselves. Instead, arrange to pass the necessary options to the C compiler independently of `CFLAGS', by writing them explicitly in the compilation commands or by defining an implicit rule, like this: CFLAGS = -g ALL_CFLAGS = -I. $(CFLAGS) .c.o: $(CC) -c $(CPPFLAGS) $(ALL_CFLAGS) $< Do include the `-g' option in `CFLAGS', because that is not _required_ for proper compilation. You can consider it a default that is only recommended. If the package is set up so that it is compiled with GCC by default, then you might as well include `-O' in the default value of `CFLAGS' as well. Put `CFLAGS' last in the compilation command, after other variables containing compiler options, so the user can use `CFLAGS' to override the others. `CFLAGS' should be used in every invocation of the C compiler, both those which do compilation and those which do linking. Every Makefile should define the variable `INSTALL', which is the basic command for installing a file into the system. Every Makefile should also define the variables `INSTALL_PROGRAM' and `INSTALL_DATA'. (The default for `INSTALL_PROGRAM' should be `$(INSTALL)'; the default for `INSTALL_DATA' should be `${INSTALL} -m 644'.) Then it should use those variables as the commands for actual installation, for executables and nonexecutables respectively. Use these variables as follows: $(INSTALL_PROGRAM) foo $(bindir)/foo $(INSTALL_DATA) libfoo.a $(libdir)/libfoo.a Optionally, you may prepend the value of `DESTDIR' to the target filename. Doing this allows the installer to create a snapshot of the installation to be copied onto the real target filesystem later. Do not set the value of `DESTDIR' in your Makefile, and do not include it in any installed files. With support for `DESTDIR', the above examples become: $(INSTALL_PROGRAM) foo $(DESTDIR)$(bindir)/foo $(INSTALL_DATA) libfoo.a $(DESTDIR)$(libdir)/libfoo.a Always use a file name, not a directory name, as the second argument of the installation commands. Use a separate command for each file to be installed.  File: make.info, Node: Directory Variables, Next: Standard Targets, Prev: Command Variables, Up: Makefile Conventions 14.4 Variables for Installation Directories =========================================== Installation directories should always be named by variables, so it is easy to install in a nonstandard place. The standard names for these variables and the values they should have in GNU packages are described below. They are based on a standard filesystem layout; variants of it are used in GNU/Linux and other modern operating systems. Installers are expected to override these values when calling `make' (e.g., `make prefix=/usr install' or `configure' (e.g., `configure --prefix=/usr'). GNU packages should not try to guess which value should be appropriate for these variables on the system they are being installed onto: use the default settings specified here so that all GNU packages behave identically, allowing the installer to achieve any desired layout. These two variables set the root for the installation. All the other installation directories should be subdirectories of one of these two, and nothing should be directly installed into these two directories. `prefix' A prefix used in constructing the default values of the variables listed below. The default value of `prefix' should be `/usr/local'. When building the complete GNU system, the prefix will be empty and `/usr' will be a symbolic link to `/'. (If you are using Autoconf, write it as `@prefix@'.) Running `make install' with a different value of `prefix' from the one used to build the program should _not_ recompile the program. `exec_prefix' A prefix used in constructing the default values of some of the variables listed below. The default value of `exec_prefix' should be `$(prefix)'. (If you are using Autoconf, write it as `@exec_prefix@'.) Generally, `$(exec_prefix)' is used for directories that contain machine-specific files (such as executables and subroutine libraries), while `$(prefix)' is used directly for other directories. Running `make install' with a different value of `exec_prefix' from the one used to build the program should _not_ recompile the program. Executable programs are installed in one of the following directories. `bindir' The directory for installing executable programs that users can run. This should normally be `/usr/local/bin', but write it as `$(exec_prefix)/bin'. (If you are using Autoconf, write it as `@bindir@'.) `sbindir' The directory for installing executable programs that can be run from the shell, but are only generally useful to system administrators. This should normally be `/usr/local/sbin', but write it as `$(exec_prefix)/sbin'. (If you are using Autoconf, write it as `@sbindir@'.) `libexecdir' The directory for installing executable programs to be run by other programs rather than by users. This directory should normally be `/usr/local/libexec', but write it as `$(exec_prefix)/libexec'. (If you are using Autoconf, write it as `@libexecdir@'.) The definition of `libexecdir' is the same for all packages, so you should install your data in a subdirectory thereof. Most packages install their data under `$(libexecdir)/PACKAGE-NAME/', possibly within additional subdirectories thereof, such as `$(libexecdir)/PACKAGE-NAME/MACHINE/VERSION'. 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. Here are the variables Makefiles should use to specify directories to put these various kinds of files in: `datarootdir' The root of the directory tree for read-only architecture-independent data files. This should normally be `/usr/local/share', but write it as `$(prefix)/share'. (If you are using Autoconf, write it as `@datarootdir@'.) `datadir''s default value is based on this variable; so are `infodir', `mandir', and others. `datadir' The directory for installing idiosyncratic read-only architecture-independent data files for this program. This is usually the same place as `datarootdir', but we use the two separate variables so that you can move these program-specific files without altering the location for Info files, man pages, etc. This should normally be `/usr/local/share', but write it as `$(datarootdir)'. (If you are using Autoconf, write it as `@datadir@'.) The definition of `datadir' is the same for all packages, so you should install your data in a subdirectory thereof. Most packages install their data under `$(datadir)/PACKAGE-NAME/'. `sysconfdir' The directory for installing read-only data files that pertain to a single machine-that is to say, files for configuring a host. Mailer and network configuration files, `/etc/passwd', and so forth belong here. All the files in this directory should be ordinary ASCII text files. This directory should normally be `/usr/local/etc', but write it as `$(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@'.) These variables specify the directory for installing certain specific types of files, if your program has them. Every GNU package should have Info files, so every program needs `infodir', but not all need `libdir' or `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 `$(prefix)/include'. (If you are using Autoconf, write it as `@includedir@'.) Most compilers other than GCC do not look for header files in directory `/usr/local/include'. So installing the header files this way is only useful with GCC. Sometimes this is not a problem because some libraries are only really intended to work with GCC. But some libraries are intended to work with other compilers. They should install their header files in two places, one specified by `includedir' and one specified by `oldincludedir'. `oldincludedir' The directory for installing `#include' header files for use with compilers other than GCC. This should normally be `/usr/include'. (If you are using Autoconf, you can write it as `@oldincludedir@'.) The Makefile commands should check whether the value of `oldincludedir' is empty. If it is, they should not try to use it; they should cancel the second installation of the header files. A package should not replace an existing header in this directory unless the header came from the same package. Thus, if your Foo package provides a header file `foo.h', then it should install the header file in the `oldincludedir' directory if either (1) there is no `foo.h' there or (2) the `foo.h' that exists came from the Foo package. To tell whether `foo.h' came from the Foo package, put a magic string in the file--part of a comment--and `grep' for that string. `docdir' The directory for installing documentation files (other than Info) for this package. By default, it should be `/usr/local/share/doc/YOURPKG', but it should be written as `$(datarootdir)/doc/YOURPKG'. (If you are using Autoconf, write it as `@docdir@'.) The YOURPKG subdirectory, which may include a version number, prevents collisions among files with common names, such as `README'. `infodir' The directory for installing the Info files for this package. By default, it should be `/usr/local/share/info', but it should be written as `$(datarootdir)/info'. (If you are using Autoconf, write it as `@infodir@'.) `infodir' is separate from `docdir' for compatibility with existing practice. `htmldir' `dvidir' `pdfdir' `psdir' Directories for installing documentation files in the particular format. (It is not required to support documentation in all these formats.) They should all be set to `$(docdir)' by default. (If you are using Autoconf, write them as `@htmldir@', `@dvidir@', etc.) Packages which supply several translations of their documentation should install them in `$(htmldir)/'LL, `$(pdfdir)/'LL, etc. where LL is a locale abbreviation such as `en' or `pt_BR'. `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@'.) `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 `$(datarootdir)/emacs/site-lisp'. If you are using Autoconf, write the default as `@lispdir@'. In order to make `@lispdir@' work, you need the following lines in your `configure.in' file: lispdir='${datarootdir}/emacs/site-lisp' AC_SUBST(lispdir) `localedir' The directory for installing locale-specific message catalogs for this package. By default, it should be `/usr/local/share/locale', but it should be written as `$(datarootdir)/locale'. (If you are using Autoconf, write it as `@localedir@'.) This directory usually has a subdirectory per locale. Unix-style man pages are installed in one of the following: `mandir' The top-level directory for installing the man pages (if any) for this package. It will normally be `/usr/local/share/man', but you should write it as `$(datarootdir)/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 datarootdir = $(prefix)/share datadir = $(datarootdir) 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 = $(datarootdir)/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: make.info, Node: Standard Targets, Next: Install Command Categories, Prev: Directory Variables, Up: Makefile Conventions 14.5 Standard Targets for Users =============================== All GNU programs should have the following targets in their Makefiles: `all' Compile the entire program. This should be the default target. This target need not rebuild any documentation files; Info files should normally be included in the distribution, and DVI files should be made only when explicitly asked for. By default, the Make rules should compile and link with `-g', so that executable programs have debugging symbols. Users who don't mind being helpless can strip the executables later if they wish. `install' Compile the program and copy the executables, libraries, and so on to the file names where they should reside for actual use. If there is a simple test to verify that a program is properly installed, this target should run that test. Do not strip executables when installing them. Devil-may-care users can use the `install-strip' target to do that. If possible, write the `install' target rule so that it does not modify anything in the directory where the program was built, provided `make all' has just been done. This is convenient for building the program under one user name and installing it under another. The commands should create all the directories in which files are to be installed, if they don't already exist. This includes the directories specified as the values of the variables `prefix' and `exec_prefix', as well as all subdirectories that are needed. One way to do this is by means of an `installdirs' target as described below. Use `-' before any command for installing a man page, so that `make' will ignore any errors. This is in case there are systems that don't have the Unix man page documentation system installed. The way to install Info files is to copy them into `$(infodir)' with `$(INSTALL_DATA)' (*note Command Variables::), and then run the `install-info' program if it is present. `install-info' is a program that edits the Info `dir' file to add or update the menu entry for the given Info file; it is part of the Texinfo package. Here is a sample rule to install an Info file: $(DESTDIR)$(infodir)/foo.info: foo.info $(POST_INSTALL) # There may be a newer info file in . than in srcdir. -if test -f foo.info; then d=.; \ else d=$(srcdir); fi; \ $(INSTALL_DATA) $$d/foo.info $(DESTDIR)$@; \ # Run install-info only if it exists. # Use `if' instead of just prepending `-' to the # line so we notice real errors from install-info. # We use `$(SHELL) -c' because some shells do not # fail gracefully when there is an unknown command. if $(SHELL) -c 'install-info --version' \ >/dev/null 2>&1; then \ install-info --dir-file=$(DESTDIR)$(infodir)/dir \ $(DESTDIR)$(infodir)/foo.info; \ else true; fi When writing the `install' target, you must classify all the commands into three categories: normal ones, "pre-installation" commands and "post-installation" commands. *Note Install Command Categories::. `install-html' `install-dvi' `install-pdf' `install-ps' These targets install documentation in formats other than Info; they're intended to be called explicitly by the person installing the package, if that format is desired. GNU prefers Info files, so these must be installed by the `install' target. When you have many documentation files to install, we recommend that you avoid collisions and clutter by arranging for these targets to install in subdirectories of the appropriate installation directory, such as `htmldir'. As one example, if your package has multiple manuals, and you wish to install HTML documentation with many files (such as the "split" mode output by `makeinfo --html'), you'll certainly want to use subdirectories, or two nodes with the same name in different manuals will overwrite each other. `uninstall' Delete all the installed files--the copies that the `install' and `install-*' targets create. This rule should not modify the directories where compilation is done, only the directories where files are installed. The uninstallation commands are divided into three categories, just like the installation commands. *Note Install Command Categories::. `install-strip' Like `install', but strip the executable files while installing them. In simple cases, this target can use the `install' target in a simple way: install-strip: $(MAKE) INSTALL_PROGRAM='$(INSTALL_PROGRAM) -s' \ install But if the package installs scripts as well as real executables, the `install-strip' target can't just refer to the `install' target; it has to strip the executables but not the scripts. `install-strip' should not strip the executables in the build directory which are being copied for installation. It should only strip the copies that are installed. Normally we do not recommend stripping an executable unless you are sure the program has no bugs. However, it can be reasonable to install a stripped executable for actual execution while saving the unstripped executable elsewhere in case there is a bug. `clean' Delete all files in the current directory that are normally created by building the program. Also delete files in other directories if they are created by this makefile. However, 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. There is no need to delete parent directories that were created with `mkdir -p', since they could have existed anyway. Delete `.dvi' files here if they are not part of the distribution. `distclean' Delete all files in the current directory (or created by this makefile) 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. However, there is no need to delete parent directories that were created with `mkdir -p', since they could have existed anyway. `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 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. Also, there is no need to delete parent directories that were created with `mkdir -p', since they could have existed anyway. These are the only exceptions; `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' `html' `pdf' `ps' Generate documentation files in the given format, if possible. Here's an example rule for generating DVI files from Texinfo: 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. Here's another example, this one for generating HTML from Texinfo: html: foo.html foo.html: foo.texi chap1.texi chap2.texi $(TEXI2HTML) $(srcdir)/foo.texi Again, you would define the variable `TEXI2HTML' in the Makefile; for example, it might run `makeinfo --no-split --html' (`makeinfo' is part of the Texinfo distribution). `dist' Create a distribution tar file for this program. The tar file should be set up so that the file names in the tar file start with a subdirectory name which is the name of the package it is a distribution for. This name can include the version number. For example, the distribution tar file of GCC version 1.40 unpacks into a subdirectory named `gcc-1.40'. The easiest way to do this is to create a subdirectory appropriately named, use `ln' or `cp' to install the proper files in it, and then `tar' that subdirectory. Compress the tar file with `gzip'. For example, the actual distribution file for GCC version 1.40 is called `gcc-1.40.tar.gz'. The `dist' target should explicitly depend on all non-source files that are in the distribution, to make sure they are up to date in the distribution. *Note Making Releases: (standards)Releases. `check' Perform self-tests (if any). The user must build the program before running the tests, but need not install the program; you should write the self-tests so that they work when the program is built but not installed. The following targets are suggested as conventional names, for programs in which they are useful. `installcheck' Perform installation tests (if any). The user must build and install the program before running the tests. You should not assume that `$(bindir)' is in the search path. `installdirs' It's useful to add a target named `installdirs' to create the directories where files are installed, and their parent directories. There is a script called `mkinstalldirs' which is convenient for this; you can find it in the Texinfo package. You can use a rule like this: # Make sure all installation directories (e.g. $(bindir)) # actually exist by making them if necessary. installdirs: mkinstalldirs $(srcdir)/mkinstalldirs $(bindir) $(datadir) \ $(libdir) $(infodir) \ $(mandir) or, if you wish to support `DESTDIR', # Make sure all installation directories (e.g. $(bindir)) # actually exist by making them if necessary. installdirs: mkinstalldirs $(srcdir)/mkinstalldirs \ $(DESTDIR)$(bindir) $(DESTDIR)$(datadir) \ $(DESTDIR)$(libdir) $(DESTDIR)$(infodir) \ $(DESTDIR)$(mandir) This rule should not modify the directories where compilation is done. It should do nothing but create installation directories. ---------- Footnotes ---------- (1) `texi2dvi' uses TeX to do the real work of formatting. TeX is not distributed with Texinfo.  File: make.info, Node: Install Command Categories, Prev: Standard Targets, Up: Makefile Conventions 14.6 Install Command Categories =============================== When writing the `install' target, you must classify all the commands into three categories: normal ones, "pre-installation" commands and "post-installation" commands. Normal commands move files into their proper places, and set their modes. They may not alter any files except the ones that come entirely from the package they belong to. Pre-installation and post-installation commands may alter other files; in particular, they can edit global configuration files or data bases. Pre-installation commands are typically executed before the normal commands, and post-installation commands are typically run after the normal commands. The most common use for a post-installation command is to run `install-info'. This cannot be done with a normal command, since it alters a file (the Info directory) which does not come entirely and solely from the package being installed. It is a post-installation command because it needs to be done after the normal command which installs the package's Info files. Most programs don't need any pre-installation commands, but we have the feature just in case it is needed. To classify the commands in the `install' rule into these three categories, insert "category lines" among them. A category line specifies the category for the commands that follow. A category line consists of a tab and a reference to a special Make variable, plus an optional comment at the end. There are three variables you can use, one for each category; the variable name specifies the category. Category lines are no-ops in ordinary execution because these three Make variables are normally undefined (and you _should not_ define them in the makefile). Here are the three possible category lines, each with a comment that explains what it means: $(PRE_INSTALL) # Pre-install commands follow. $(POST_INSTALL) # Post-install commands follow. $(NORMAL_INSTALL) # Normal commands follow. If you don't use a category line at the beginning of the `install' rule, all the commands are classified as normal until the first category line. If you don't use any category lines, all the commands are classified as normal. These are the category lines for `uninstall': $(PRE_UNINSTALL) # Pre-uninstall commands follow. $(POST_UNINSTALL) # Post-uninstall commands follow. $(NORMAL_UNINSTALL) # Normal commands follow. Typically, a pre-uninstall command would be used for deleting entries from the Info directory. If the `install' or `uninstall' target has any dependencies which act as subroutines of installation, then you should start _each_ dependency's commands with a category line, and start the main target's commands with a category line also. This way, you can ensure that each command is placed in the right category regardless of which of the dependencies actually run. Pre-installation and post-installation commands should not run any programs except for these: [ basename bash cat chgrp chmod chown cmp cp dd diff echo egrep expand expr false fgrep find getopt grep gunzip gzip hostname install install-info kill ldconfig ln ls md5sum mkdir mkfifo mknod mv printenv pwd rm rmdir sed sort tee test touch true uname xargs yes The reason for distinguishing the commands in this way is for the sake of making binary packages. Typically a binary package contains all the executables and other files that need to be installed, and has its own method of installing them--so it does not need to run the normal installation commands. But installing the binary package does need to execute the pre-installation and post-installation commands. Programs to build binary packages work by extracting the pre-installation and post-installation commands. Here is one way of extracting the pre-installation commands (the `-s' option to `make' is needed to silence messages about entering subdirectories): make -s -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: $0 ~ /^(normal-install|post-install)[ \t]*$/ {on = 0} on {print $0} $0 ~ /^pre-install[ \t]*$/ {on = 1}  File: make.info, Node: Quick Reference, Next: Error Messages, Prev: Makefile Conventions, Up: Top Appendix A Quick Reference ************************** This appendix summarizes the directives, text manipulation functions, and special variables which GNU `make' understands. *Note Special Targets::, *Note Catalogue of Implicit Rules: Catalogue of Rule