This chapter describes conventions for writing 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.
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.
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. A makefile target like
foo.o : bar.c $(CC) $(CFLAGS) -I. -I$(srcdir) -c bar.c -o foo.o
should instead be written as
foo.o : bar.c $(CC) $(CFLAGS) $< -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 -s $(srcdir)/sedscript $(srcdir)/foo.man > foo.1
All GNU programs should have the following targets in their Makefiles:
info: foo.info foo.info: $(srcdir)/foo.texi $(MAKEINFO) -o foo.info $(srcdir)/foo.texi
dvi: foo.dvi foo.dvi: $(srcdir)/foo.texi $(TEXI2DVI) $(srcdir)/foo.texiPlease make sure that `$(TEXI2DVI)' is defined in the Makefile.
makewill ignore any errors. This is in case there are systems that don't have the Unix man page documentation system installed.
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.
Makefile : $(srcdir)/Makefile.in $(SHELL) config.status
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 = $(CFLAGS) -I. .c.o: $(CC) -c $(ALL_CFLAGS) $(CPPFLAGS) $<
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.
Every Makefile should define the variable
INSTALL, which is the
basic command for installing a file into the system.
Every Makefile should also define 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:
prefixshould be `/usr/local' (at least for now).
$(exec_prefix)is used for directories that contain machine-specific files (such as executables and subroutine libraries), while
$(prefix)is used directly for other directories.
libdirshould normally be `/usr/local/lib', but it should be written as `$(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.
# Common prefix for installation directories. # NOTE: This directory must exist when you start installation. prefix = /usr/local exec_prefix = $(prefix) # Directory in which to put the executable for the command `gcc' bindir = $(exec_prefix)/bin # Directory in which to put the directories used by the compiler. libdir = $(exec_prefix)/lib # Directory in which 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.