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.)
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) $(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 $(srcdir)/foo.man > foo.1
Write the Makefile commands (and any shell scripts, such as
configure) to run in sh, not in csh. Don't use any
special features of ksh or bash.
The configure script and the Makefile rules for building and
installation should not use any utilities directly except these:
cat cmp cp echo egrep expr grep ln mkdir mv pwd rm rmdir sed test touch
Stick to the generally supported options for these programs. For example, don't use `mkdir -p', convenient as it may be, because most systems don't support it.
The Makefile rules for building and installation can also use compilers
and related programs, but should do so via make variables so that the
user can substitute alternatives. Here are some of the programs we
mean:
ar bison cc flex install ld lex make makeinfo ranlib texi2dvi yacc
When you use ranlib, you should test whether it exists, and run
it only if it exists, so that the distribution will work on systems that
don't have ranlib.
If you use symbolic links, you should implement a fallback for systems that don't have symbolic links.
It is ok to use other utilities in Makefile portions (or scripts) intended only for particular systems where you know those utilities to exist.
All GNU programs should have the following targets in their Makefiles:
prefix and
exec_prefix, as well as all subdirectories that are needed.
One way to do this is by means of an installdirs target
as described below.
Use `-' before any command for installing a man page, so that
make will ignore any errors. This is in case there are systems
that don't have the Unix man page documentation system installed.
The way to install Info files is to copy them into `$(infodir)'
with $(INSTALL_DATA) (see section Variables for Specifying Commands), and then run
the install-info program if it is present. install-info
is 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.
One exception, however: `make realclean' should not delete
`configure' even if `configure' can be remade using a rule in
the Makefile. More generally, `make realclean' should not delete
anything that needs to exist in order to run `configure'
and then begin to build the program.
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.
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. Alternatively, write just the dependencies, and allow GNU
Make to provide the command.
ln or cp to install the proper files in it, and
then tar that subdirectory.
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.
See section `Making Releases' in GNU Coding Standards.
The following targets are suggested as conventional names, for programs in which they are useful.
installcheck
installdirs
# Make sure all installation directories (e.g. $(bindir))
# actually exist by making them if necessary.
installdirs: mkinstalldirs
$(srcdir)/mkinstalldirs $(bindir) $(datadir) \
$(libdir) $(infodir) \
$(mandir)
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.
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:
prefix should be `/usr/local'
(at least for now).
exec_prefix should
be $(prefix).
Generally, $(exec_prefix) is used for directories that contain
machine-specific files (such as executables and subroutine libraries),
while $(prefix) is used directly for other directories.
libdir should normally be
`/usr/local/lib', but write it as `$(exec_prefix)/lib'.
includedir and one
specified by oldincludedir.
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.
configure shell script.
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. libdir = $(exec_prefix)/lib # 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.