3.1 Depth

automake supports three kinds of directory hierarchy: “flat”, “shallow”, and “deep”.

A flat package is one in which all the files are in a single directory. The Makefile.am for such a package by definition lacks a SUBDIRS macro. An example of such a package is termutils.

A deep package is one in which all the source lies in subdirectories; the top level directory contains mainly configuration information. GNU cpio is a good example of such a package, as is GNU tar. The top level Makefile.am for a deep package will contain a SUBDIRS macro, but no other macros to define objects which are built.

A shallow package is one in which the primary source resides in the top-level directory, while various parts (typically libraries) reside in subdirectories. automake is one such package (as is GNU make, which does not currently use automake).

3.2 Strictness

While Automake is intended to be used by maintainers of GNU packages, it does make some effort to accomodate those who wish to use it, but do not want to use all the GNU conventions.

To this end, Automake supports three levels of strictness – the strictness indicating how stringently Automake should check standards conformance.

The valid strictness levels are:

‘foreign’

Automake will check for only those things which are absolutely required for proper operations. For instance, whereas GNU standards dictate the existence of a NEWS file, it will not be required in this mode. The name comes from the fact that Automake is intended to be used for GNU programs; these relaxed rules are not the standard mode of operation.

‘gnu’

Automake will check – as much as possible – for compliance to the GNU standards for packages. This is the default.

‘gnits’

Automake will check for compliance to the as-yet-unwritten GNITS standards. These are based on the GNU standards, but are even more detailed. Unless you are a GNITS standards contributor, it is recommended that you avoid this option until such time as the GNITS standard is actually published.

3.3 The Uniform Naming Scheme

Automake variables generally follow a uniform naming scheme that makes it easy to decide how programs (and other derived objects) are built, and how they are installed. This scheme also supports configure time determination of what should be built.

At make time, certain variables are used to determine which objects are to be built. These variables are called primary variables. For instance, the primary variable PROGRAMS holds a list of programs which are to be compiled and linked.

A different set of variables is used to decide where the built objects should be installed. These variables are named after the primary variables, but have a prefix indicating which standard directory should be used as the installation directory. The standard directory names are given in the GNU standards (see Directory Variables in The GNU Coding Standards). automake extends this list with pkglibdir, pkgincludedir, and pkgdatadir; these are the same as the non-‘pkg’ versions, but with ‘@PACKAGE@’ appended.

For each primary, there is one additional variable named by prepending ‘EXTRA_’ to the primary name. This variable is used to list objects which may or may not be built, depending on what configure decides. This variable is required because Automake must know the entire list of objects to be built in order to generate a Makefile.in that will work in all cases.

For instance, cpio decides at configure time which programs are built. Some of the programs are installed in bindir, and some are installed in sbindir:

EXTRA_PROGRAMS = mt rmt
bin_PROGRAMS = cpio pax
sbin_PROGRAMS = @PROGRAMS@

Defining a primary variable is an error.

Note that the common ‘dir’ suffix is left off when constructing the variable names; thus one writes ‘bin_PROGRAMS’ and not ‘bindir_PROGRAMS’.

Not every sort of object can be installed in every directory. Automake will flag those attempts it finds in error. Automake will also diagnose obvious misspellings in directory names.

Sometimes the standard directories – even as augmented by Automake – are not enough. In particular it is sometimes useful, for clarity, to install objects in a subdirectory of some predefined directory. To this end, Automake allows you to extend the list of possible installation directories. A given prefix (eg ‘zar’) is valid if a variable of the same name with ‘dir’ appended is defined (eg ‘zardir’).

For instance, until HTML support is part of Automake, you could use this to install raw HTML documentation:

htmldir = $(prefix)/html
html_DATA = automake.html

The special prefix ‘noinst’ indicates that the objects in question should not be installed at all.

The special prefix ‘check’ indicates that the objects in question should not be built until the make check command is run.

Possible primary names are ‘PROGRAMS’, ‘LIBRARIES’, ‘SCRIPTS’, ‘DATA’, ‘HEADERS’, ‘MANS’, and ‘TEXINFOS’.

3.4 General Operation

Automake essentially works by reading a Makefile.am and generating a Makefile.in. The macro definitions and targets in the Makefile.am are copied into the generated file.

Automake tries to group comments with adjoining targets (or variable definitions) in an intelligent way.

A target defined in Makefile.am generally overrides any such target of a similar name that would be automatically generated by automake. Although this is a supported feature, it is generally best to avoid making use of it, as sometimes the generated rules are very particular.

Automake also allows a form of comment which is not copied into the output; all lines beginning with ‘##’ are completely ignored by Automake.

It is customary to make the first line of Makefile.am read:

## Process this file with automake to produce Makefile.in

6.1 Building a program

In a directory containing source that gets built into a program (as opposed to a library), the ‘PROGRAMS’ primary is used. Programs can be installed in bindir, sbindir, libexecdir, pkglibdir, or not at all.

For instance:

bin_PROGRAMS = hello

In this simple case, the resulting Makefile.in will contain code to generate a program named hello. The variable hello_SOURCES is used to specify which source files get built into an executable:

hello_SOURCES = hello.c

This causes hello.c to be compiled into hello.o, and then linked to produce hello.

If ‘prog_SOURCES’ is needed, but not specified, then it defaults to the single file prog.c. Id est in the example above, the definition of hello_SOURCES is actually redundant.

Multiple programs can be built in a single directory. Multiple programs can share a single source file. The source file must be listed in each ‘_SOURCES’ definition.

Header files listed in a ‘_SOURCES’ definition will be ignored. Lex (‘.l’) and yacc (‘.y’) files can also be listed; support for these should work but is still preliminary.

Sometimes it is useful to determine the programs that are to be built at configure time. For instance, GNU cpio only builts mt and rmt under special circumstances.

In this case, you must notify Automake of all the programs that can possibly be built, but at the same time cause the generated Makefile.in to use the programs specified by configure. This is done by having configure substitute values into each ‘_PROGRAMS’ definition, while listing all optionally built programs in EXTRA_PROGRAMS.

If you need to link against libraries that are not found by configure, you can use LDADD to do so. This variable actually can be used to add any options to the linker command line.

Sometimes, multiple programs are built in one directory but do not share the same link-time requirements. In this case, you can use the ‘prog_LDADD’ variable (where PROG is the name of the program as it appears in some ‘_PROGRAMS’ variable, and usually written in lowercase) to override the global LDADD. (If this variable exists for a given program, then that program is not linked using LDADD.)

For instance, in GNU cpio, pax, cpio, and mt are linked against the library libcpio.a. However, rmt is built in the same directory, and has no such link requirement. Also, mt and rmt are only built on certain architectures. Here is what cpio’s src/Makefile.am looks like (abridged):

bin_PROGRAMS = cpio pax @MT@
libexec_PROGRAMS = @RMT@
EXTRA_PROGRAMS = mt rmt

LDADD = ../lib/libcpio.a @INTLLIBS@
rmt_LDADD =

cpio_SOURCES = …
pax_SOURCES = …
mt_SOURCES = …
rmt_SOURCES = …

It is also occasionally useful to have a program depend on some other target which is not actually part of that program. This can be done using the ‘prog_DEPENDENCIES’ variable. Each program depends on the contents of such a variable, but no further interpretation is done.

Since program names are rewritten into Makefile macro names, program names must follow Makefile macro syntax. Sometimes it is useful to have a program whose name does not follow such rules. In these cases, Automake canonicalizes the program name. All characters in the name except for letters, numbers, and the underscore are turned into underscores when making macro references. Eg, if your program is named sniff-glue, you would use sniff_glue_SOURCES, not sniff-glue_SOURCES.

6.2 Building a library

Building a library is much like building a program. In this case, the name of the primary is ‘LIBRARIES’. Libraries can be installed in libdir or pkglibdir.

Each ‘_LIBRARIES’ variable is a list of the base names of libraries to be built. For instance to create a library named libcpio.a, but not install it, you would write:

noinst_LIBRARIES = cpio

The sources that go into a library are determined exactly as they are for programs, via the ‘_SOURCES’ variables. Note that programs and libraries share a namespace, so one cannot have a program (lob) and a library (liblob.a) with the same name in one directory.

Extra objects can be added to a library using the ‘library_LIBADD’ variable. This should be used for objects determined by configure. Again from cpio:

cpio_LIBADD = @LIBOBJS@ @ALLOCA@

Note that Automake explicitly recognizes the use of @LIBOBJS@ and @ALLOCA@ in the above example, and uses this information, plus the list of LIBOBJS files derived from configure.in to automatically include the appropriate source files in the distribution (see What Goes in a Distribution). These source files are also automatically handled in the dependency-tracking scheme, see See Automatic dependency tracking.

6.3 Automatic de-ANSI-fication

Although the GNU standards prohibit it, some GNU programs are written in ANSI C; see FIXME. This is possible because each source file can be “de-ANSI-fied” before the actual compilation takes place.

If the Makefile.am variable AUTOMAKE_OPTIONS (Changing Automake’s Behavior) contains the option ansi2knr then code to handle de-ANSI-fication is inserted into the generated Makefile.in.

This causes each source file to be treated as ANSI C. If an ANSI C compiler is available, it is used.

This support requires the source files ansi2knr.c and ansi2knr.1 to be in the same directory as the ANSI C source; these files are distributed with Automake. Also, the package configure.in must call the macro fp_C_PROTOTYPES.

6.4 Automatic dependency tracking

As a developer it is often painful to continually update the Makefile.in whenever the include-file dependencies change in a project. automake supplies a way to automatically track dependency changes, and distribute the dependencies in the generated Makefile.in.

Currently this support requires the use of GNU make and gcc. It might become possible in the future to supply a different dependency generating program, if there is enough demand.

This mode is enabled by default if any C program or library is defined in the current directory.

When you decide to make a distribution, the dist target will re-run automake with the ‘--include-deps’ option. This causes the previously generated dependencies to be inserted into the generated Makefile.in, and thus into the distribution. ‘--include-deps’ also turns off inclusion of the dependency generation code.

This mode can be suppressed by putting no-dependencies in the variable AUTOMAKE_OPTIONS.

7.1 Executable Scripts

It is possible to define and install programs which are scripts. Such programs are listed using the ‘SCRIPTS’ primary name. automake doesn’t define any dependencies for scripts; the Makefile.am should include the appropriate rules.

automake does not assume that scripts are derived objects; such objects are must be deleted by hand; see What Gets Cleaned for more information.

automake itself is a script that is generated at configure time from automake.in. Here is how this is handled:

bin_SCRIPTS = automake

Since automake appears in the AC_OUTPUT macro, dependencies for it are automatically generated.

Script objects can be installed in bindir, sbindir, libexecdir, or pkgdatadir.

7.2 Header files

Header files are specified by the ‘HEADERS’ family of variables. Generally header files are not installed, so the noinst_HEADERS variable will be the most used.

All header files must be listed somewhere; missing ones will not appear in the distribution. Often it is most convenient to list uninstalled headers with the rest of the sources for a program. See Building a program.

Headers can be installed in includedir, oldincludedir, or pkgincludedir.

7.3 Architecture-independent data files

Automake supports the installation of miscellaneous data files using the ‘DATA’ family of variables.

Such data can be installed in the directories datadir, sysconfdir, sharedstatedir, localstatedir, or pkgdatadir.

All such data files are included in the distribution.

Here is how autoconf installs its auxiliary data files:

pkgdata_DATA = clean-kr.am clean.am compile-kr.am compile-vars.am \
compile.am data.am depend.am dist-subd-top.am dist-subd-vars.am \
dist-subd.am dist-vars.am dist.am footer.am header-vars.am header.am \
libscripts.am libprograms.am libraries-vars.am libraries.am library.am \
mans-vars.am mans.am packagedata.am program.am programs.am remake-hdr.am \
remake-subd.am remake.am scripts.am subdirs.am tags.am tags-subd.am \
texinfos-vars.am texinfos.am hack-make.sed nl-remove.sed

7.4 Built sources

Occasionally a file which would otherwise be called “source” (eg a C ‘.h’ file) is actually derived from some other file. Such files should be listed in the BUILT_SOURCES variable.

Files listed in BUILT_SOURCES are built before any automatic dependency tracking is done. Built sources are included in a distribution.

8.1 Texinfo

If the current directory contains Texinfo source, you must declare it with the ‘TEXINFOS’ primary. Generally Texinfo files are converted into info, and thus the info_TEXINFOS macro is most commonly used here. Note that any Texinfo source file must end in the ‘.texi’ extension (‘.texinfo’ won’t work).

If the ‘.texi’ file @includes version.texi, then that file will be automatically generated. version.texi defines three Texinfo macros you can reference: EDITION, VERSION, and UPDATED. The first two hold the version number of your package (but are kept separate for clarity); the last is the date the primary file was last modified. The version.texi support requires the mdate-sh program; this program is supplied with Automake.

Sometimes an info file actually depends on more than one ‘.texi’ file. For instance, in the xdvik distribution, kpathsea.texi includes the files install.texi, copying.texi, and freedom.texi. You can tell Automake about these dependencies using the ‘texi_TEXINFOS’ variable. Here is how xdvik could do it:

info_TEXINFOS = kpathsea.texi
kpathsea_TEXINFOS = install.texi copying.texi freedom.texi

Automake will warn if a directory containing Texinfo source does not also contain the file texinfo.tex. This file is supplied with Automake.

Automake generates an install-info target; some people apparently use this.

8.2 Man pages

A package can also include man pages. (Though see the GNU standards on this matter, Man Pages in The GNU Coding Standards.) Man pages are declared using the ‘MANS’ primary. Generally the man_MANS macro is used. Man pages are automatically installed in the correct subdirectory of mandir, based on the file extension.

By default, man pages are installed by ‘make install’. However, since the GNU project does not require man pages, many maintainers do not expend effort to keep the man pages up to date. In these cases, the no-installman option will prevent the man pages from being installed by default. The user can still explicitly install them via ‘make install-man’.

Here is how the documentation is handled in GNU cpio (which includes both Texinfo documentation and man pages):

info_TEXINFOS = cpio.texi
man_MANS = cpio.1 mt.1

Texinfo source, info pages and man pages are all considered to be source for the purposes of making a distribution.

14.1 Interfacing to etags

automake will generate rules to generate TAGS files for use with GNU Emacs under some circumstances.

If any C source code or headers are present, then a tags target will be generated for the directory.

At the topmost directory of a multi-directory package, a tags target file will be generated which, when run, will generate a TAGS file that includes by reference all TAGS files from subdirectories.

Also, if the variable ETAGS_ARGS is defined, a tags target will be generated. This variable is intended for use in directories which contain taggable source that etags does not understand.

Here is how Automake generates tags for its source, and for nodes in its Texinfo file:

ETAGS_ARGS = automake.in --lang=none \
 --regex='/^@node[ \t]+\([^,]+\)/\1/' automake.texi

Automake will also generate an ID target which will run mkid on the source. This is only supported on a directory-by-directory basis.

14.2 Handling new file extensions

It is sometimes useful to introduce a new implicit rule to handle a file type that Automake does not know about. If this is done, you must notify GNU Make of the new suffixes. This can be done by putting a list of new suffixes in the SUFFIXES variable.

14.3 Built sources

FIXME write this

17.1 The simplest GNU program

hello is renowned for its classic simplicity and versatility. What better place to begin a tour? The below shows what could be used as the Hello distribution’s Makefile.am.

bin_PROGRAMS = hello
hello_SOURCES = hello.c version.c getopt.c getopt1.c getopt.h
hello_LDADD = @ALLOCA@
info_TEXINFOS = hello.texi
hello_TEXINFOS = gpl.texi

EXTRA_DIST = testdata

check-local: hello
        @echo expect no output from diff
        ./hello > test.out
        diff -c $(srcdir)/testdata test.out
        rm -f test.out

Of course, Automake also requires some minor changes to configure.in. The new configure.in would read:

dnl Process this file with autoconf to produce a configure script.
AC_INIT(hello.c)
VERSION=1.3
AC_SUBST(VERSION)
PACKAGE=hello
AC_SUBST(PACKAGE)
AC_PROG_CC
AC_PROG_CPP
AC_PROG_INSTALL
AC_STDC_HEADERS
AC_HAVE_HEADERS(string.h fcntl.h sys/file.h)
AC_ALLOCA
AC_OUTPUT(Makefile)

If Hello were really going to use Automake, the version.c file would probably be deleted, or changed so as to be automatically generated.

17.2 A tricker example

Here is another, trickier example. It shows how to generate two programs (ctags and etags) from the same source file (etags.c). The difficult part is that each compilation of etags.c requires different cpp flags.

bin_PROGRAMS = etags ctags
ctags_SOURCES =
ctags_LDADD = ctags.o
ctags_DEPENDENCIES = ctags.o

etags.o:
        $(COMPILE) -DETAGS_REGEXPS etags.c

ctags.o:
        $(COMPILE) -DCTAGS -o ctags.o etags.c

Note that ctags_SOURCES is defined to be empty – that way no implicit value is substituted. The implicit value, however, is used to generate etags from etags.o.

ctags_LDADD is used to get ctags.o into the link line, while ctags_DEPENDENCIES exists to make sure that ctags.o gets built in the first place.

This is a somewhat pathological example.

17.3 Automake uses itself

Automake, of course, uses itself to generate its Makefile.in. Since Automake is a shallow package, it has more than one Makefile.am. Here is the top-level Makefile.am:

## Process this file with automake to create Makefile.in

AUTOMAKE_OPTIONS = gnits
MAINT_CHARSET = latin1
PERL = @PERL@

SUBDIRS = tests

bin_SCRIPTS = automake
info_TEXINFOS = automake.texi

pkgdata_DATA = clean-kr.am clean.am compile-kr.am compile-vars.am \
compile.am data.am depend.am \
dist-vars.am footer.am header.am header-vars.am \
kr-vars.am libraries-vars.am \
libraries.am library.am mans-vars.am \
program.am programs.am remake-hdr.am \
remake-subd.am remake.am scripts.am subdirs.am tags.am tags-subd.am \
tags-clean.am \
texi-version.am texinfos-vars.am texinfos.am \
libraries-clean.am programs-clean.am data-clean.am \
COPYING INSTALL texinfo.tex \
ansi2knr.c ansi2knr.1 \
aclocal.m4

## These must all be executable when installed.
pkgdata_SCRIPTS = config.guess config.sub install-sh mdate-sh mkinstalldirs

CLEANFILES = automake

# The following requires a fixed version of the Emacs 19.30 etags.
ETAGS_ARGS = automake.in --lang=none \
 --regex='/^@node[ \t]+\([^,]+\)/\1/' automake.texi

## `test -x' is not portable.  So we use Perl instead.  If Perl
## doesn't exist, then this test is meaningless anyway.
# Check to make sure some installed files are executable.
installcheck-local:
	$(PERL) -e "exit ! -x '$(pkgdatadir)/config.guess';"
	$(PERL) -e "exit ! -x '$(pkgdatadir)/config.sub';"
	$(PERL) -e "exit ! -x '$(pkgdatadir)/install-sh';"
	$(PERL) -e "exit ! -x '$(pkgdatadir)/mdate-sh';"
	$(PERL) -e "exit ! -x '$(pkgdatadir)/mkinstalldirs';"

# Some simple checks:
# * syntax check with perl4 and perl5.
# * make sure the scripts don't use 'true'
# * expect no instances of '${...}'
# These are only really guaranteed to work on my machine.
maintainer-check: automake check
	$(PERL) -c -w automake
	@if grep '^[^#].*true' $(srcdir)/[a-z]*.am; then \
	  echo "can't use 'true' in GNU Makefile" 1>&2; \
	  exit 1;				\
	else :; fi
	@if test `fgrep '$${' $(srcdir)/[a-z]*.am | wc -l` -ne 0; then \
	  echo "found too many uses of '\$${'" 1>&2; \
	  exit 1;				\
	fi
	if $(SHELL) -c 'perl4.036 -v' >/dev/null 2>&1; then \
	  perl4.036 -c -w automake; \
	else :; fi

# Tag before making distribution.  Also, don't make a distribution if
# checks fail.  Also, make sure the NEWS file is up-to-date.
cvs-dist: maintainer-check
	@if sed 1q NEWS | grep -e "$(VERSION)" > /dev/null; then :; else \
	  echo "NEWS not updated; not releasing" 1>&2; \
	  exit 1;				\
	fi
	cvs tag `echo "Release-$(VERSION)" | sed 's/\./-/g'`
	$(MAKE) dist

As you can see, Automake defines many of its own rules, to make the maintainer’s job easier. For instance the cvs-dist rule automatically tags the current version in the CVS repository, and then makes a standard distribution.

Automake consists primarily of one program, automake, and a number of auxiliary scripts. Automake also installs a number of programs which are possibly installed via the ‘--add-missing’ option; these scripts are listed in the pkgdata_SCRIPTS variable.

Automake also has a tests subdirectory, as indicated in the SUBDIRS variable above. Here is tests/Makefile.am:

## Process this file with automake to create Makefile.in

AUTOMAKE_OPTIONS = gnits

TESTS = mdate.test vtexi.test acoutput.test instexec.test checkall.test \
acoutnoq.test acouttbs.test libobj.test proginst.test acoutqnl.test \
confincl.test spelling.test prefix.test badprog.test depend.test

EXTRA_DIST = defs

This is where all the tests are really run. defs is an initialization file used by each test script; it is explicitly mentioned because automake has no way of automatically finding it.

17.4 A deep hierarchy

The GNU textutils are a collection of programs for manipulating text files. They are distributed as a deep package. The textutils have only recently been modified to use Automake; the examples come from a prerelease.

Here is the top-level Makefile.am:

SUBDIRS = lib src doc man

In the lib directory, a library is built which is used by each textutil. Here is lib/Makefile.am:

noinst_LIBRARIES = tu

EXTRA_DIST = rx.c regex.c

tu_SOURCES = error.h getline.h getopt.h linebuffer.h \
long-options.h md5.h regex.h rx.h xstrtod.h xstrtol.h xstrtoul.h \
error.c full-write.c getline.c getopt.c getopt1.c \
linebuffer.c long-options.c md5.c memchr.c safe-read.c \
xmalloc.c xstrtod.c xstrtol.c xstrtoul.c

tu_LIBADD = @REGEXOBJ@ @LIBOBJS@ @ALLOCA@

The src directory contains the source for all the textutils – 23 programs in all. The Makefile.am for this directory also includes some simple checking code, and constructs a version.c file on the fly:

bin_PROGRAMS = cat cksum comm csplit cut expand fmt fold head join md5sum \
nl od paste pr sort split sum tac tail tr unexpand uniq wc

noinst_HEADERS = system.h version.h
DISTCLEANFILES = stamp-v version.c

INCLUDES = -I$(top_srcdir)/lib

LDADD = version.o ../lib/libtu.a

$(PROGRAMS): version.o ../lib/libtu.a

AUTOMAKE_OPTIONS = ansi2knr

version.c: stamp-v
stamp-v: Makefile
	rm -f t-version.c
	echo '#include <config.h>' > t-version.c
	echo '#include "version.h"' >> t-version.c
	echo 'const char *version_string = "'GNU @PACKAGE@ @VERSION@'";' \
		>> t-version.c
	if cmp -s version.c t-version.c; then	\
	  rm t-version.c;			\
	else					\
	  mv t-version.c version.c;		\
	fi
	echo timestamp > $@

check: md5sum
	./md5sum \
	 --string="" \
	 --string="a" \
	 --string="abc" \
	 --string="message digest" \
	 --string="abcdefghijklmnopqrstuvwxyz" \
	 --string="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789" \
	 --string="12345678901234567890123456789012345678901234567890123456789012345678901234567890" \
       | diff -c $(srcdir)/md5-test.rfc -

The doc directory builds the info documentation for the textutils:

info_TEXINFOS = textutils.texi

And, last, the man directory installs the man pages for all the textutils:

man_MANS = cat.1 cksum.1 comm.1 csplit.1 cut.1 expand.1 fmt.1 fold.1 head.1 \
join.1 md5sum.1 nl.1 od.1 paste.1 pr.1 sort.1 split.1 sum.1 tac.1 tail.1 \
tr.1 unexpand.1 uniq.1 wc.1

You can now see how easy it is to handle even a largish project using Automake.