This chapter describes conventions for writing the Makefiles for GNU programs.
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 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 > $@
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
configure script and the Makefile rules for building and
installation should not use any utilities directly except these:
cat cmp cp echo egrep expr grep ln mkdir mv pwd rm rmdir sed test touch
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.
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
ar bison cc flex install ld lex make makeinfo ranlib texi2dvi yacc
Use the following
$(AR) $(BISON) $(CC) $(FLEX) $(INSTALL) $(LD) $(LEX) $(MAKE) $(MAKEINFO) $(RANLIB) $(TEXI2DVI) $(YACC)
When you use
ranlib, you should make sure nothing bad happens if
the system does not have
ranlib. Arrange to ignore an error
from that command, and print a message before the command to tell the
user that failure of the
ranlib command does not mean a problem.
If you use symbolic links, you should implement a fallback for systems that don't have symbolic links.
It is ok to use other utilities in Makefile portions (or scripts) intended only for particular systems where you know those utilities to exist.
All GNU programs should have the following targets in their Makefiles:
installtarget rule so that it does not modify anything in the directory where the program was built, provided `make all' has just been done. This is convenient for building the program under one user name and installing it under another. The commands should create all the directories in which files are to be installed, if they don't already exist. This includes the directories specified as the values of the variables
exec_prefix, as well as all subdirectories that are needed. One way to do this is by means of an
installdirstarget as described below. Use `-' before any command for installing a man page, so that
makewill ignore any errors. This is in case there are systems that don't have the Unix man page documentation system installed. The way to install Info files is to copy them into `$(infodir)' with
$(INSTALL_DATA)(see section Variables for Specifying Commands), and then run the
install-infoprogram if it is present.
install-infois a script that edits the Info `dir' file to add or update the menu entry for the given Info file; it will be part of the Texinfo package. Here is a sample rule to install an Info file:
$(infodir)/foo.info: foo.info # There may be a newer info file in . than in srcdir. -if test -f foo.info; then d=.; \ else d=$(srcdir); fi; \ $(INSTALL_DATA) $$d/foo.info $@; \ # Run install-info only if it exists. # Use `if' instead of just prepending `-' to the # line so we notice real errors from install-info. # We use `$(SHELL) -c' because some shells do not # fail gracefully when there is an unknown command. if $(SHELL) -c 'install-info --version' \ >/dev/null 2>&1; then \ install-info --infodir=$(infodir) $$d/foo.info; \ else true; fi
distclean, plus more: C source files produced by Bison, tags tables, Info files, and so on. The reason we say "almost everything" is that `make maintainer-clean' should not delete `configure' even if `configure' can be remade using a rule in the Makefile. More generally, `make maintainer-clean' should not delete anything that needs to exist in order to run `configure' and then begin to build the program. This is the only exception;
maintainer-cleanshould delete everything else that can be rebuilt. The `maintainer-clean' 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
maintainer-cleanshould start with these two:
@echo "This command is intended for maintainers to use;" @echo "it deletes files that may require special tools to rebuild."
info: foo.info foo.info: foo.texi chap1.texi chap2.texi $(MAKEINFO) $(srcdir)/foo.texiYou must define the variable
MAKEINFOin the Makefile. It should run the
makeinfoprogram, which is part of the Texinfo distribution.
dvi: foo.dvi foo.dvi: foo.texi chap1.texi chap2.texi $(TEXI2DVI) $(srcdir)/foo.texiYou must define the variable
TEXI2DVIin the Makefile. It should run the program
texi2dvi, which is part of the Texinfo distribution. Alternatively, write just the dependencies, and allow GNU Make to provide the command.
cpto install the proper files in it, and then
tarthat subdirectory. The
disttarget should explicitly depend on all non-source files that are in the distribution, to make sure they are up to date in the distribution. See section `Making Releases' in GNU Coding Standards.
The following targets are suggested as conventional names, for programs in which they are useful.
# Make sure all installation directories (e.g. $(bindir)) # actually exist by making them if necessary. installdirs: mkinstalldirs $(srcdir)/mkinstalldirs $(bindir) $(datadir) \ $(libdir) $(infodir) \ $(mandir)This rule should not modify the directories where compilation is done. It should do nothing but create installation directories.
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
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
BISONFLAGS. (The name
CFLAGS is an exception to
this rule, but we keep it because it is standard.) Use
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
If there are C compiler options that must be used for proper
compilation of certain files, do not include them in
Users expect to be able to specify
CFLAGS freely themselves.
Instead, arrange to pass the necessary options to the C compiler
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.
CFLAGS last in the compilation command, after other variables
containing compiler options, so the user can use
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_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.
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.
prefixshould be `/usr/local' When building the complete GNU system, the prefix will be empty and `/usr' will be a symbolic link to `/'.
$(exec_prefix)is used for directories that contain machine-specific files (such as executables and subroutine libraries), while
$(prefix)is used directly for other directories.
Executable programs are installed in one of the following directories.
Data files used by the program during its execution are divided into categories in two ways.
This makes for six different possibilities. However, we want to discourage the use of architecture-dependent files, aside from of object files and libraries. It is much cleaner to make other data files architecture-independent, and it is generally not hard.
Therefore, here are the variables makefiles should use to specify directories:
libdirshould normally be `/usr/local/lib', but write it as `$(exec_prefix)/lib'.
includedirand one specified by
oldincludediris 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
oldincludedirdirectory 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:
And finally, you should set the following variable:
# 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.