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This chapter describes conventions for writing the Makefiles for GNU programs.
| 1.1 General Conventions for Makefiles | ||
| 1.2 Utilities in Makefiles | ||
| 1.3 Standard Targets for Users | ||
| 1.4 Variables for Specifying Commands | ||
| 1.5 Variables for Installation Directories |
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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 > $@
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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
Use the following make variables:
$(AR) $(BISON) $(CC) $(FLEX) $(INSTALL) $(LD) $(LEX) $(MAKE) $(MAKEINFO) $(RANLIB) $(TEXI2DVI) $(YACC)
When you use ranlib, you should make sure nothing bad happens if
the system does not have ranlib. Arrange to ignore an error
from that command, and print a message before the command to tell the
user that failure of the ranlib command does not mean a problem.
If you use symbolic links, you should implement a fallback for systems that don’t have symbolic links.
It is ok to use other utilities in Makefile portions (or scripts) intended only for particular systems where you know those utilities to exist.
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All GNU programs should have the following targets in their Makefiles:
Compile the entire program. This should be the default target. This target need not rebuild any documentation files; Info files should normally be included in the distribution, and DVI files should be made only when explicitly asked for.
Compile the program and copy the executables, libraries, and so on to the file names where they should reside for actual use. If there is a simple test to verify that a program is properly installed, this target should run that test.
The commands should create all the directories in which files are to be
installed, if they don’t already exist. This includes the directories
specified as the values of the variables prefix and
exec_prefix, as well as all subdirectories that are needed.
One way to do this is by means of an installdirs target
as described below.
Use ‘-’ before any command for installing a man page, so that
make will ignore any errors. This is in case there are systems
that don’t have the Unix man page documentation system installed.
The way to install Info files is to copy them into ‘$(infodir)’
with $(INSTALL_DATA) (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
Delete all the installed files that the ‘install’ target would create (but not the noninstalled files such as ‘make all’ would create).
Delete all files from the current directory that are normally created by building the program. 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.
Delete ‘.dvi’ files here if they are not part of the distribution.
Delete all files from the current directory 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.
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.
Delete everything from the current directory 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.
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.
Update a tags table for this program.
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.
Generate DVI files for all TeXinfo documentation. For example:
dvi: foo.dvi
foo.dvi: foo.texi chap1.texi chap2.texi
$(TEXI2DVI) $(srcdir)/foo.texi
You must define the variable TEXI2DVI in the Makefile. It should
run the program texi2dvi, which is part of the Texinfo
distribution. Alternatively, write just the dependencies, and allow GNU
Make to provide the command.
Create a distribution tar file for this program. The tar file should be set up so that the file names in the tar file start with a subdirectory name which is the name of the package it is a distribution for. This name can include the version number.
For example, the distribution tar file of GCC version 1.40 unpacks into a subdirectory named ‘gcc-1.40’.
The easiest way to do this is to create a subdirectory appropriately
named, use ln or cp to install the proper files in it, and
then tar that subdirectory.
The dist target should explicitly depend on all non-source files
that are in the distribution, to make sure they are up to date in the
distribution.
See Making Releases in GNU Coding Standards.
Perform self-tests (if any). The user must build the program before running the tests, but need not install the program; you should write the self-tests so that they work when the program is built but not installed.
The following targets are suggested as conventional names, for programs in which they are useful.
installcheckPerform installation tests (if any). The user must build and install the program before running the tests. You should not assume that ‘$(bindir)’ is in the search path.
installdirsIt’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; 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)
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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.
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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.
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 ‘/’.
A prefix used in constructing the default values of some of the
variables listed below. The default value of exec_prefix should
be $(prefix).
Generally, $(exec_prefix) is used for directories that contain
machine-specific files (such as executables and subroutine libraries),
while $(prefix) is used directly for other directories.
Executable programs are installed in one of the following directories.
The directory for installing executable programs that users can run. This should normally be ‘/usr/local/bin’, but write it as ‘$(exec_prefix)/bin’.
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 ‘$(exec_prefix)/sbin’.
The directory for installing executable programs to be run by other programs rather than by users. This directory should normally be ‘/usr/local/libexec’, but write it as ‘$(exec_prefix)/libexec’.
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:
The directory for installing read-only architecture independent data files. This should normally be ‘/usr/local/share’, but write it as ‘$(prefix)/share’. As a special exception, see ‘$(infodir)’ and ‘$(includedir)’ below.
The directory for installing read-only data files that pertain to a single machine–that is to say, files for configuring a host. Mailer and network configuration files, ‘/etc/passwd’, and so forth belong here. All the files in this directory should be ordinary ASCII text files. This directory should normally be ‘/usr/local/etc’, but write it as ‘$(prefix)/etc’.
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 ‘$(localstatedir)’.
The directory for installing architecture-independent data files which the programs modify while they run. This should normally be ‘/usr/local/com’, but write it as ‘$(prefix)/com’.
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 ‘$(prefix)/var’.
The directory for object files and libraries of object code. Do not
install executables here, they probably belong in ‘$(libexecdir)’
instead. The value of libdir should normally be
‘/usr/local/lib’, but write it as ‘$(exec_prefix)/lib’.
The directory for installing the Info files for this package. By default, it should be ‘/usr/local/info’, but it should be written as ‘$(prefix)/info’.
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 ‘$(prefix)/include’.
Most compilers other than GCC do not look for header files in
‘/usr/local/include’. So installing the header files this way is
only useful with GCC. Sometimes this is not a problem because some
libraries are only really intended to work with GCC. But some libraries
are intended to work with other compilers. They should install their
header files in two places, one specified by includedir and one
specified by oldincludedir.
The directory for installing ‘#include’ header files for use with compilers other than GCC. This should normally be ‘/usr/include’.
The Makefile commands should check whether the value of
oldincludedir is empty. If it is, they should not try to use
it; they should cancel the second installation of the header files.
A package should not replace an existing header in this directory unless
the header came from the same package. Thus, if your Foo package
provides a header file ‘foo.h’, then it should install the header
file in the oldincludedir directory if either (1) there is no
‘foo.h’ there or (2) the ‘foo.h’ that exists came from the Foo
package.
To tell whether ‘foo.h’ came from the Foo package, put a magic string in the file—part of a comment—and grep for that string.
Unix-style man pages are installed in one of the following:
The directory for installing the man pages (if any) for this package. It should include the suffix for the proper section of the manual—usually ‘1’ for a utility. It will normally be ‘/usr/local/man/man1’, but you should write it as ‘$(prefix)/man/man1’.
The directory for installing section 1 man pages.
The directory for installing section 2 man pages.
Use these names instead of ‘mandir’ if the package needs to install man pages in more than one section of the manual.
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.
The file name extension for the installed man page. This should contain a period followed by the appropriate digit; it should normally be ‘.1’.
The file name extension for installed section 1 man pages.
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:
The directory for the sources being compiled. The value of this
variable is normally inserted by the 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. 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.
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