2.1 General Operation

Automake works by reading a Makefile.am and generating a Makefile.in. Certain macros and targets defined in the Makefile.am instruct automake to generate more specialized code; for instances a ‘bin_PROGRAMS’ macro definition will cause targets for compiling and linking to be generated.

The macro definitions and targets in the Makefile.am are copied into the generated file. This allows you to add arbitrary code into the generated Makefile.in. For instance the Automake distribution includes a non-standard cvs-dist target, which the Automake maintainer uses to make distributions from his source control system.

Note that GNU make extensions are not recognized by Automake. Using such extensions in a Makefile.am will lead to errors or confusing behavior.

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.

Similarly, a variable defined in Makefile.am will override any definition of the variable that automake would ordinarily create. This feature is more often useful than the ability to override a target definition. Be warned that many of the variables generated by automake are considered to be for internal use only, and their names might change in future releases.

When examining a variable definition, Automake will recursively examine variables referenced in the definition. E.g., if Automake is looking at the content of ‘foo_SOURCES’ in this snippet

xs = a.c b.c
foo_SOURCES = c.c $(xs)

it would use the files a.c, b.c, and c.c as the contents of ‘foo_SOURCES’.

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

2.2 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).

2.3 Strictness

While Automake is intended to be used by maintainers of GNU packages, it does make some effort to accommodate 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.

For more information on the precise implications of the strictness level, see See The effect of --gnu and --gnits.

2.4 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 instance, pkglibdir is defined as $(datadir)/@PACKAGE@.

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 statically 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 without a prefix (eg PROGRAMS) 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’, ‘LISP’, ‘SCRIPTS’, ‘DATA’, ‘HEADERS’, ‘MANS’, and ‘TEXINFOS’.

2.5 How derived variables are named

Sometimes a Makefile variable name is derived from some text the user supplies. For instance program names are rewritten into Makefile macro names. Automake canonicalizes this text, so that it does not have to follow Makefile variable naming rules. All characters in the name except for letters, numbers, and the underscore are turned into underscores when making macro references. E.g., if your program is named sniff-glue, the derived variable name would be sniff_glue_SOURCES, not sniff-glue_SOURCES.

3.1 A simple example, start to finish

Let’s suppose you just finished writing zardoz, a program to make your head float from vortex to vortex. You’ve been using autoconf to provide a portability framework, but your Makefile.ins have been ad-hoc. You want to make them bulletproof, so you turn to automake.

The first step is to update your configure.in to include the commands that automake needs. The simplest way to do this is to add an AM_INIT_AUTOMAKE call near the beginning:

AM_INIT_AUTOMAKE(zardoz, 1.0)

Since your program doesn’t have any complicating factors (e.g., it doesn’t use gettext, it doesn’t want to build a shared library), you’re done with this part. That was easy!

Now you must regenerate configure. But to do that, you’ll need to tell autoconf how to find the new macro you’ve used. The easiest way to do this is to use the aclocal program to generate your aclocal.m4 for you. But wait... you already have an aclocal.m4, because you had to write some hairy macros for your program. aclocal lets you put your own macros into acinclude.m4, so simply rename and then run:

mv aclocal.m4 acinclude.m4
aclocal
autoconf

Now it is time to write your Makefile.am for zardoz. zardoz is a user program, so you want to install it where the rest of the user programs go. zardoz also has some Texinfo documentation. Your configure.in script uses AC_REPLACE_FUNCS, so you need to link against ‘@LIBOBJS@’. So here’s what you’d write:

bin_PROGRAMS = zardoz
zardoz_SOURCES = main.c head.c float.c vortex9.c gun.c
zardoz_LDADD = @LIBOBJS@

info_TEXINFOS = zardoz.texi

Now you can run automake --add-missing to generate your Makefile.in and grab any auxiliary files you might need, and you’re done!

3.2 A classic program

hello is renowned for its classic simplicity and versatility. This section shows how Automake could be used with the Hello package. The examples below are from the latest GNU Hello, but all the maintainer-only code has been stripped out, as well as all copyright comments.

Of course, GNU Hello is somewhat more featureful than your traditional two-liner. GNU Hello is internationalized, does option processing, and has a manual and a test suite. GNU Hello is a deep package.

Here is the configure.in from GNU Hello:

dnl Process this file with autoconf to produce a configure script.
AC_INIT(src/hello.c)
AM_INIT_AUTOMAKE(hello, 1.3.11)
AM_CONFIG_HEADER(config.h)

dnl Set of available languages.
ALL_LINGUAS="de fr es ko nl no pl pt sl sv"

dnl Checks for programs.
AC_PROG_CC
AC_ISC_POSIX

dnl Checks for libraries.

dnl Checks for header files.
AC_STDC_HEADERS
AC_HAVE_HEADERS(string.h fcntl.h sys/file.h sys/param.h)

dnl Checks for library functions.
AC_FUNC_ALLOCA

dnl Check for st_blksize in struct stat
AC_ST_BLKSIZE

dnl internationalization macros
AM_GNU_GETTEXT
AC_OUTPUT([Makefile doc/Makefile intl/Makefile po/Makefile.in \
           src/Makefile tests/Makefile tests/hello],
   [chmod +x tests/hello])

The ‘AM_’ macros are provided by Automake (or the Gettext library); the rest are standard Autoconf macros.

The top-level Makefile.am:

EXTRA_DIST = BUGS ChangeLog.O
SUBDIRS = doc intl po src tests

As you can see, all the work here is really done in subdirectories.

The po and intl directories are automatically generated using gettextize; they will not be discussed here.

In doc/Makefile.am we see:

info_TEXINFOS = hello.texi
hello_TEXINFOS = gpl.texi

This is sufficient to build, install, and distribute the Hello manual.

Here is tests/Makefile.am:

TESTS = hello
EXTRA_DIST = hello.in testdata

The script hello is generated by configure, and is the only test case. make check will run this test.

Last we have src/Makefile.am, where all the real work is done:

bin_PROGRAMS = hello
hello_SOURCES = hello.c version.c getopt.c getopt1.c getopt.h system.h 
hello_LDADD = @INTLLIBS@ @ALLOCA@
localedir = $(datadir)/locale
INCLUDES = -I../intl -DLOCALEDIR=\"$(localedir)\"

3.3 Building etags and ctags

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

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

ctags.o: etags.c
        $(COMPILE) -DCTAGS -o ctags.o -c 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. ctags_DEPENDENCIES is generated by Automake.

The above rules won’t work if your compiler doesn’t accept both ‘-c’ and ‘-o’. The simplest fix for this is to introduce a bogus dependency (to avoid problems with a parallel make):

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

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

Also, these explicit rules do not work if the de-ANSI-fication feature is used; supporting that requires a little more work:

etags._o: etags._c ctags.o
        $(COMPILE) -DETAGS_REGEXPS -c etags.c

ctags._o: etags._c
        $(COMPILE) -DCTAGS -c etags.c && mv etags._o ctags.o

5.1 Configuration requirements

The simplest way to meet the basic Automake requirements is to use the macro AM_INIT_AUTOMAKE (FIXME: xref). But if you prefer, you can do the required steps by hand:

• Define the variables PACKAGE and VERSION with AC_SUBST. PACKAGE should be the name of the package as it appears when bundled for distribution. For instance, Automake defines PACKAGE to be ‘automake’. VERSION should be the version number of the release that is being developed. We recommend that you make configure.in the only place in your package where the version number is defined; this makes releases simpler.

  Automake doesn’t do any interpretation of PACKAGE or VERSION, except in ‘Gnits’ mode (FIXME xref).

• Use the macro AC_ARG_PROGRAM if a program or script is installed.
• Use AC_PROG_MAKE_SET if the package is not flat.
• Use AM_SANITY_CHECK to make sure the build environment is sane.
• Use AM_PROG_INSTALL if any scripts (see Executable Scripts) are installed by the package. Otherwise, use AC_PROG_INSTALL.
• Use AM_MISSING_PROG to see whether the programs aclocal, autoconf, automake, autoheader, and makeinfo are in the build environment. Here is how this is done:

  missing_dir=`cd $ac_aux_dir && pwd`
  AM_MISSING_PROG(ACLOCAL, aclocal, $missing_dir)
  AM_MISSING_PROG(AUTOCONF, autoconf, $missing_dir)
  AM_MISSING_PROG(AUTOMAKE, automake, $missing_dir)
  AM_MISSING_PROG(AUTOHEADER, autoheader, $missing_dir)
  AM_MISSING_PROG(MAKEINFO, makeinfo, $missing_dir)
  

Here are the other macros which Automake requires but which are not run by AM_INIT_AUTOMAKE:

AC_OUTPUT

Automake uses this to determine which files to create. Listed files named Makefile are treated as Makefiles. Other listed files are treated differently. Currently the only difference is that a Makefile is removed by make distclean, while other files are removed by make clean.

5.2 Other things Automake recognizes

Automake will also recognize the use of certain macros and tailor the generated Makefile.in appropriately. Currently recognized macros and their effects are:

AC_CONFIG_HEADER

Automake requires the use of AM_CONFIG_HEADER, which is similar to AC_CONFIG_HEADER but does some useful Automake-specific work.

AC_CONFIG_AUX_DIR

Automake will look for various helper scripts, such as mkinstalldirs, in the directory named in this macro invocation. If not seen, the scripts are looked for in their “standard” locations (either the top source directory, or in the source directory corresponding to the current Makefile.am, whichever is appropriate). FIXME: give complete list of things looked for in this directory

AC_PATH_XTRA

Automake will insert definitions for the variables defined by AC_PATH_XTRA into each Makefile.in that builds a C program or library.

AC_CANONICAL_HOST

AC_CHECK_TOOL

Automake will ensure that config.guess and config.sub exist. Also, the Makefile variables ‘host_alias’ and ‘host_triplet’ are introduced.

AC_CANONICAL_SYSTEM

This is similar to AC_CANONICAL_HOST, but also defines the Makefile variables ‘build_alias’ and ‘target_alias’.

AC_FUNC_ALLOCA

AC_FUNC_GETLOADAVG

AC_FUNC_MEMCMP

AC_STRUCT_ST_BLOCKS

AC_FUNC_FNMATCH

AM_FUNC_STRTOD

AC_REPLACE_FUNCS

AC_REPLACE_GNU_GETOPT

AM_WITH_REGEX

Automake will ensure that the appropriate dependencies are generated for the objects corresponding to these macros. Also, Automake will verify that the appropriate source files are part of the distribution. Note that Automake does not come with any of the C sources required to use these macros, so automake -a will not install the sources. See Building a library for more information.

LIBOBJS

Automake will detect statements which put ‘.o’ files into LIBOBJS, and will treat these additional files as if they were discovered via AC_REPLACE_FUNCS.

AC_PROG_RANLIB

This is required if any libraries are built in the package.

AC_PROG_CXX

This is required if any C++ source is included.

AM_PROG_LIBTOOL

Automake will turn on processing for libtool (see The Libtool Manual in The Libtool Manual).

AC_PROG_YACC

If a Yacc source file is seen, then you must either use this macro or define the variable ‘YACC’ in configure.in. The former is preferred.

AC_DECL_YYTEXT

This macro is required if there is Lex source in the package.

AC_PROG_LEX

If a Lex source file is seen, then this macro must be used.

ALL_LINGUAS

If Automake sees that this variable is set in configure.in, it will check the po directory to ensure that all the named ‘.po’ files exist, and that all the ‘.po’ files that exist are named.

AM_C_PROTOTYPES

This is required when using automatic de-ANSI-fication, see Automatic de-ANSI-fication.

AM_GNU_GETTEXT

This macro is required for packages which use GNU gettext (see Gettext). It is distributed with gettext. If Automake sees this macro it ensures that the package meets some of gettext’s requirements.

AM_MAINTAINER_MODE

This macro adds a ‘--enable-maintainer-mode’ option to configure. If this is used, automake will cause “maintainer-only” rules to be turned off by default in the generated Makefile.ins. This macro is disallowed in ‘Gnits’ mode. FIXME xref.

AC_SUBST

AC_CHECK_TOOL

AC_CHECK_PROG

AC_CHECK_PROGS

AC_PATH_PROG

AC_PATH_PROGS

For each of these macros, the first argument is automatically defined as a variable in each generated Makefile.in.

5.3 Auto-generating aclocal.m4

Automake includes a number of Autoconf macros which can be used in your package; some of them are actually required by Automake in certain situations. These macros must be defined in your aclocal.m4; otherwise they will not be seen by autoconf.

The aclocal program will automatically generate aclocal.m4 files based on the contents of configure.in. This provides a convenient way to get Automake-provided macros, without having to search around. Also, the aclocal mechanism is extensible for use by other packages.

At startup, aclocal scans all the ‘.m4’ files it can find, looking for macro definitions. Then it scans configure.in. Any mention of one of the macros found in the first step causes that macro, and any macros it in turn requires, to be put into aclocal.m4.

The contents of acinclude.m4, if it exists, are also automatically included in aclocal.m4. This is useful for incorporating local macros into configure.

aclocal accepts the following options:

--acdir=dir

Look for the macro files in dir instead of the installation directory. This is typically used for debugging.

--help

Print a summary of the command line options and exit.

-I dir

Add the directory dir to the list of directories searched for ‘.m4’ files.

--output=file

Cause the output to be put into file instead of aclocal.m4.

--verbose

Print the names of the files it examines.

--version

Print the version number of Automake and exit.

5.4 Autoconf macros supplied with Automake

AM_CONFIG_HEADER

Automake will generate rules to automatically regenerate the config header. If you do use this macro, you must create the file stamp-h.in in your source directory. It can be empty.

AM_CYGWIN32

Check to see if this configure is being run in the ‘Cygwin32’ environment. (FIXME xref). If so, define output variable EXEEXT to ‘.exe’; otherwise define it to the empty string. Automake recognizes this macro and uses it to generate Makefile.ins which will automatically work under ‘Cygwin32’. In the ‘Cygwin32’ environment, gcc generates executables whose names end in ‘.exe’, even if this was not specified on the command line. Automake adds special code to Makefile.in to gracefully deal with this.

AM_FUNC_STRTOD

If the strtod function is not available, or does not work correctly (like the one on SunOS 5.4), add strtod.o to output variable LIBOBJS.

AM_FUNC_ERROR_AT_LINE

If the function error_at_line is not found, then add error.o to LIBOBJS.

AM_FUNC_MKTIME

Check for a working mktime function. If not found, add mktime.o to ‘LIBOBJS’.

AM_FUNC_OBSTACK

Check for the GNU obstacks code; if not found, add obstack.o to ‘LIBOBJS’.

AM_C_PROTOTYPES

Check to see if function prototypes are understood by the compiler. If so, define ‘PROTOTYPES’ and set the output variables ‘U’ and ‘ANSI2KNR’ to the empty string. Otherwise, set ‘U’ to ‘_’ and ‘ANSI2KNR’ to ‘./ansi2knr’. Automake uses these values to implement automatic de-ANSI-fication.

AM_HEADER_TIOCGWINSZ_NEEDS_SYS_IOCTL

If the use of TIOCGWINSZ requires <sys/ioctl.h>, then define GWINSZ_IN_SYS_IOCTL. Otherwise TIOCGWINSZ can be found in <termios.h>.

AM_INIT_AUTOMAKE

Runs many macros that most configure.in’s need. This macro has two required arguments, the package and the version number. By default this macro AC_DEFINE’s ‘PACKAGE’ and ‘VERSION’. This can be avoided by passing in a non-empty third argument.

AM_PATH_LISPDIR

Searches for the program emacs, and, if found, sets the output variable lispdir to the full path to Emacs’ site-lisp directory.

AM_PROG_CC_STDC

If the C compiler in not in ANSI C mode by default, try to add an option to output variable CC to make it so. This macro tries various options that select ANSI C on some system or another. It considers the compiler to be in ANSI C mode if it defines __STDC__ to 1 and handles function prototypes correctly.

If you use this macro, you should check after calling it whether the C compiler has been set to accept ANSI C; if not, the shell variable am_cv_prog_cc_stdc is set to ‘no’. If you wrote your source code in ANSI C, you can make an un-ANSIfied copy of it by using the ansi2knr option.

AM_PROG_INSTALL

Like AC_PROG_INSTALL, but also defines INSTALL_SCRIPT.

AM_SANITY_CHECK

This checks to make sure that a file created in the build directory is newer than a file in the source directory. This can fail on systems where the clock is set incorrectly. This macro is automatically run from AM_INIT_AUTOMAKE.

AM_SYS_POSIX_TERMIOS

Check to see if POSIX termios headers and functions are available on the system. If so, set the shell variable am_cv_sys_posix_termios to ‘yes’. If not, set the variable to ‘no’.

AM_TYPE_PTRDIFF_T

Define ‘HAVE_PTRDIFF_T’ if the type ‘ptrdiff_t’ is defined in <stddef.h>.

AM_WITH_DMALLOC

Add support for the dmalloc package. If the user configures with ‘--with-dmalloc’, then define WITH_DMALLOC and add ‘-ldmalloc’ to LIBS. The dmalloc package can be found at ftp://ftp.letters.com/src/dmalloc/dmalloc.tar.gz

AM_WITH_REGEX

Adds ‘--with-regex’ to the configure command line. If specified (the default), then the ‘regex’ regular expression library is used, regex.o is put into ‘LIBOBJS’, and ‘WITH_REGEX’ is defined.. If ‘--without-regex’ is given, then the ‘rx’ regular expression library is used, and rx.o is put into ‘LIBOBJS’.

5.5 Writing your own aclocal macros

Aclocal doesn’t have any built-in knowledge of any macros, so it is easy to extend it with your own macros.

This is mostly used for libraries which want to supply their own Autoconf macros for use by other programs. For instance the gettext library supplies a macro AM_GNU_GETTEXT which should be used by any package using gettext. When the library is installed, it installs this macro so that aclocal will find it.

A file of macros should be a series of AC_DEFUN’s. Aclocal also understands AC_REQUIRE, so it is safe to put each macro in a separate file.

A macro file’s name should end in ‘.m4’. Such files should be installed in $(datadir)/aclocal.

7.1 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 (‘noinst’).

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 version.c getopt.c getopt1.c getopt.h system.h 

This causes each mentioned ‘.c’ file to be compiled into the corresponding ‘.o’. Then all are linked to produce hello.

If ‘prog_SOURCES’ is needed, but not specified, then it defaults to the single file prog.c. 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 included in the distribution but otherwise ignored. In case it isn’t obvious, you should not include the header file generated by configure in an ‘_SOURCES’ variable; this file should not be distributed. Lex (‘.l’) and yacc (‘.y’) files can also be listed; see Yacc and Lex support.

Automake must know all the source files that could possibly go into a program, even if not all the files are built in every circumstance. Any files which are only conditionally built should be listed in the appropriate ‘EXTRA_’ variable. For instance, if hello-linux.c were conditionally included in hello, the Makefile.am would contain:

EXTRA_hello_SOURCES = hello-linux.c

Similarly, sometimes it is useful to determine the programs that are to be built at configure time. For instance, GNU cpio only builds 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 = …

‘prog_LDADD’ is inappropriate for passing program-specific linker flags (except for ‘-l’ and ‘-L’). So, use the ‘prog_LDFLAGS’ variable for this purpose.

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.

If ‘prog_DEPENDENCIES’ is not supplied, it is computed by Automake. The automatically-assigned value is the contents of ‘prog_LDADD’, with most configure substitutions, ‘-l’, and ‘-L’ options removed. The configure substitutions that are left in are only ‘@LIBOBJS@’ and ‘@ALLOCA@’; these are left because it is known that they will not cause an invalid value for ‘prog_DEPENDENCIES’ to be generated.

7.2 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.

See Building a Shared Library, for information on how to build shared libraries using Libtool and the ‘LTLIBRARIES’ primary.

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

noinst_LIBRARIES = libcpio.a

The sources that go into a library are determined exactly as they are for programs, via the ‘_SOURCES’ variables. Note that the library name is canonicalized (see How derived variables are named), so the ‘_SOURCES’ variable corresponding to liblob.a is ‘liblob_a_SOURCES’, not ‘liblob.a_SOURCES’.

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:

libcpio_a_LIBADD = @LIBOBJS@ @ALLOCA@

7.3 Special handling for LIBOBJS and ALLOCA

Automake explicitly recognizes the use of @LIBOBJS@ and @ALLOCA@, 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.

@LIBOBJS@ and @ALLOCA@ are specially recognized in any ‘_LDADD’ or ‘_LIBADD’ variable.

7.4 Building a Shared Library

Building shared libraries is a relatively complex matter. For this reason, GNU Libtool (see The Libtool Manual in The Libtool Manual) was created to help build shared libraries in a platform-independent way.

Automake uses Libtool to build libraries declared with the ‘LTLIBRARIES’ primary. Each ‘_LTLIBRARIES’ variable is a list of shared libraries to build. For instance, to create a library named libgettext.a and its corresponding shared libraries, and install them in ‘libdir’, write:

lib_LTLIBRARIES = libgettext.la

Note that shared libraries must be installed, so ‘noinst_LTLIBRARIES’ and ‘check_LTLIBRARIES’ are not allowed.

For each library, the ‘library_LIBADD’ variable contains the names of extra libtool objects (‘.lo’ files) to add to the shared library. The ‘library_LDFLAGS’ variable contains any additional libtool flags, such as ‘-version-info’ or ‘-static’.

Where an ordinary library might include @LIBOBJS@, a libtool library must use @LTLIBOBJS@. This is required because the object files that libtool operates on do not necessarily end in ‘.o’. The libtool manual contains more details on this topic.

For libraries installed in some directory, automake will automatically supply the appropriate ‘-rpath’ option. However, for libraries determined at configure time (and thus mentioned in EXTRA_LTLIBRARIES), automake does not know the eventual installation directory; for such libraries you must add the ‘-rpath’ option to the appropriate ‘_LDFLAGS’ variable by hand.

See The Libtool Manual in The Libtool Manual, for more information.

7.5 Variables used when building a program

Occasionally it is useful to know which Makefile variables Automake uses for compilations; for instance you might need to do your own compilation in some special cases.

Some variables are inherited from Autoconf; these are CC, CFLAGS, CPPFLAGS, DEFS, LDFLAGS, and LIBS.

There are some additional variables which Automake itself defines:

INCLUDES

A list of ‘-I’ options. This can be set in your Makefile.am if you have special directories you want to look in. automake already provides some ‘-I’ options automatically. In particular it generates ‘-I$(srcdir)’ and a ‘-I’ pointing to the directory holding config.h (if you’ve used AC_CONFIG_HEADER or AM_CONFIG_HEADER).

INCLUDES can actually be used for other cpp options besides ‘-I’. For instance, it is sometimes used to pass arbitrary ‘-D’ options to the compiler.

COMPILE

This is the command used to actually compile a C source file. The filename is appended to form the complete command line.

LINK

This is the command used to actually link a C program.

7.6 Yacc and Lex support

Automake has somewhat idiosyncratic support for Yacc and Lex.

Automake assumes that the ‘.c’ file generated by yacc (or lex) should be named using the basename of the input file. That is, for a yacc source file foo.y, automake will cause the intermediate file to be named foo.c (as opposed to y.tab.c, which is more traditional).

The extension of a yacc source file is used to determine the extension of the resulting ‘C’ or ‘C++’ file. Files with the extension ‘.y’ will be turned into ‘.c’ files; likewise, ‘.yy’ will become ‘.cc’; ‘.y++’, ‘c++’; and ‘.yxx’, ‘.cxx’. Likewise, lex source files can be used to generate ‘C’ or ‘C++’; the extensions ‘.l’, ‘.ll’, ‘.l++’, and ‘.lxx’ are recognized.

You should never explicitly mention the intermediate (‘C’ or ‘C++’) file in any ‘SOURCES’ variable; only list the source file.

The intermediate files generated by yacc (or lex) will be included in any distribution that is made. That way the user doesn’t need to have yacc or lex.

If a yacc source file is seen, then your configure.in must define the variable ‘YACC’. This is most easily done by invoking the macro ‘AC_PROG_YACC’.

Similarly, if a lex source file is seen, then your configure.in must define the variable ‘LEX’. You can use ‘AC_PROG_LEX’ to do this. Automake’s lex support also requires that you use the ‘AC_DECL_YYTEXT’ macro—automake needs to know the value of ‘LEX_OUTPUT_ROOT’.

Any program including a lex source file must be linked against ‘@LEXLIB@’. You can do this by putting ‘@LEXLIB@’ into the appropriate ‘LDADD’ variable.

Automake makes it possible to include multiple yacc (or lex) source files in a single program. Automake uses a small program called ylwrap to run yacc (or lex) in a subdirectory. This is necessary because yacc’s output filename is fixed, and a parallel make could conceivably invoke more than one instance of yacc simultaneously. ylwrap is distributed with automake. It should appear in the directory specified by ‘AC_CONFIG_AUX_DIR’, or the current directory if that macro is not used in configure.in.

For yacc, simply managing locking is insufficient. yacc output also always uses the same symbol names internally, so it isn’t possible to link two yacc parsers into the same executable.

We recommend using the following renaming hack used in gdb:

#define	yymaxdepth c_maxdepth
#define	yyparse	c_parse
#define	yylex	c_lex
#define	yyerror	c_error
#define	yylval	c_lval
#define	yychar	c_char
#define	yydebug	c_debug
#define	yypact	c_pact	
#define	yyr1	c_r1			
#define	yyr2	c_r2			
#define	yydef	c_def		
#define	yychk	c_chk		
#define	yypgo	c_pgo		
#define	yyact	c_act		
#define	yyexca	c_exca
#define yyerrflag c_errflag
#define yynerrs	c_nerrs
#define	yyps	c_ps
#define	yypv	c_pv
#define	yys	c_s
#define	yy_yys	c_yys
#define	yystate	c_state
#define	yytmp	c_tmp
#define	yyv	c_v
#define	yy_yyv	c_yyv
#define	yyval	c_val
#define	yylloc	c_lloc
#define yyreds	c_reds
#define yytoks	c_toks
#define yylhs	c_yylhs
#define yylen	c_yylen
#define yydefred c_yydefred
#define yydgoto	c_yydgoto
#define yysindex c_yysindex
#define yyrindex c_yyrindex
#define yygindex c_yygindex
#define yytable	 c_yytable
#define yycheck	 c_yycheck

For each define, replace the ‘c_’ prefix with whatever you like. These defines work for bison, byacc, and traditional yaccs. If you find a parser generator that uses a symbol not covered here, please report the new name so it can be added to the list.

7.7 C++ and other languages

Automake includes full support for C++, and rudimentary support for other languages. Support for other languages will be improved based on demand.

Any package including C++ code must define the output variable ‘CXX’ in configure.in; the simplest way to do this is to use the AC_PROG_CXX macro.

A few additional variables are defined when a C++ source file is seen:

CXX

The name of the C++ compiler.

CXXFLAGS

Any flags to pass to the C++ compiler.

CXXCOMPILE

The command used to actually compile a C++ source file. The file name is appended to form the complete command line.

CXXLINK

The command used to actually link a C++ program.

7.8 Automatic de-ANSI-fication

Although the GNU standards allow the use of ANSI C, this can have the effect of limiting portability of a package to some older compilers (notably SunOS).

Automake allows you to work around this problem on such machines by “de-ANSI-fying” each source file 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 C source file in the directory to be treated as ANSI C. If an ANSI C compiler is available, it is used. If no ANSI C compiler is available, the ansi2knr program is used to convert the source files into K&R C, which is then compiled.

The ansi2knr program is simple-minded. It assumes the source code will be formatted in a particular way; see the ansi2knr man page for details.

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

Automake also handles finding the ansi2knr support files in some other directory in the current package. This is done by prepending the relative path to the appropriate directory to the ansi2knr option. For instance, suppose the package has ANSI C code in the src and lib subdirs. The files ansi2knr.c and ansi2knr.1 appear in lib. Then this could appear in src/Makefile.am:

AUTOMAKE_OPTIONS = ../lib/ansi2knr

If no directory prefix is given, the files are assumed to be in the current directory.

7.9 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. In the meantime, this mode is enabled by default if any C program or library is defined in the current directory, so you may get a ‘Must be a separator’ error from non-GNU make.

When you decide to make a distribution, the dist target will re-run automake with ‘--include-deps’ and other options. This will cause the previously generated dependencies to be inserted into the generated Makefile.in, and thus into the distribution. This step also turns off inclusion of the dependency generation code, so that those who download your distribution but don’t use GNU make and gcc will not get errors.

When added to the Makefile.in, the dependencies have all system-specific dependencies automatically removed. This can be done by listing the files in ‘OMIT_DEPENDENCIES’. For instance all references to system header files are removed by automake. Sometimes it is useful to specify that a certain header file should be removed. For instance if your configure.in uses ‘AM_WITH_REGEX’, then any dependency on rx.h or regex.h should be removed, because the correct one cannot be known until the user configures the package.

As it turns out, automake is actually smart enough to the particular case of the regular expression header. It will also automatically omit libintl.h if ‘AM_GNU_GETTEXT’ is used.

Automatic dependency tracking can be suppressed by putting no-dependencies in the variable AUTOMAKE_OPTIONS.

If you unpack a distribution made by make dist, and you want to turn on the dependency-tracking code again, simply re-run automake.

The actual dependency files are put under the build directory, in a subdirectory named .deps. These depencencies are machine specific. It is safe to delete them if you like; they will be automatically recreated during the next build.

8.1 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 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, a target for it is automatically generated.

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

8.2 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 clearest to list uninstalled headers with the rest of the sources for a program. See Building a program. Headers listed in a ‘_SOURCES’ variable need not be listed in any ‘_HEADERS’ variable.

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

8.3 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.

By default, data files are not included in a distribution.

Here is how automake installs its auxiliary data files:

pkgdata_DATA = clean-kr.am clean.am …

8.4 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.

Built sources are also not compiled by default. You must either explicitly mention them in some other ‘_SOURCES’ variable for this to happen.

Note that, in some cases, BUILT_SOURCES will work in somewhat suprising ways. In order to get the built sources to work with automatic dependency tracking, the Makefile must depend on $(BUILT_SOURCES). This can cause these sources to be rebuilt at what might seem like funny times.

9.1 Emacs Lisp

Automake provides some support for Emacs Lisp. The ‘LISP’ primary is used to hold a list of ‘.el’ files. Possible prefixes for this primary are ‘lisp_’ and ‘noinst_’. Note that if lisp_LISP is defined, then configure.in must run AM_PATH_LISPDIR (fixme xref).

By default Automake will byte-compile all Emacs Lisp source files using the Emacs found by AM_PATH_LISPDIR. If you wish to avoid byte-compiling, simply define the variable ‘ELCFILES’ to be empty. Byte-compiled Emacs Lisp files are not portable among all versions of Emacs, so it makes sense to turn this off if you expect sites to have more than one version of Emacs installed. Furthermore, many packages don’t actually benefit from byte-compilation. Still, we recommand that you leave it enabled by default. It is probably better for sites with strange setups to cope for themselves than to make the installation less nice for everybody else.

9.2 Gettext

If AM_GNU_GETTEXT is seen in configure.in, then Automake turns on support for GNU gettext, a message catalog system for internationalization (see GNU Gettext in GNU gettext utilities).

The gettext support in Automake requires the addition of two subdirectories to the package, intl and po. Automake ensure that these directories exist and are mentioned in SUBDIRS.

Furthermore, Automake checks that the definition of ‘ALL_LINGUAS’ in configure.in corresponds to all the valid ‘.po’ files, and nothing more.

9.3 Guile

Automake provides some automatic support for writing Guile modules. Automake will turn on Guile support if the AM_INIT_GUILE_MODULE macro is used in configure.in.

Right now Guile support just means that the AM_INIT_GUILE_MODULE macro is understood to mean:

• AM_INIT_AUTOMAKE is run.
• AC_CONFIG_AUX_DIR is run, with a path of ...

As the Guile module code matures, no doubt the Automake support will grow as well.

9.4 Libtool

Automake provides support for GNU Libtool (see The Libtool Manual in The Libtool Manual) with the ‘LTLIBRARIES’ primary. See Building a Shared Library.

10.1 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’ or ‘.texinfo’ extension.

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 GNU Hello, hello.texi includes the file gpl.texi. You can tell Automake about these dependencies using the ‘texi_TEXINFOS’ variable. Here is how Hello does it:

info_TEXINFOS = hello.texi
hello_TEXINFOS = gpl.texi

By default, Automake requires the file texinfo.tex to appear in the same directory as the Texinfo source. However, if you used AC_CONFIG_AUX_DIR in configure.in, then texinfo.tex is looked for there. Automake supplies texinfo.tex if ‘--add-missing’ is given.

If your package has Texinfo files in many directories, you can use the variable TEXINFO_TEX to tell automake where to find the canonical texinfo.tex for your package. The value of this variable should be the relative path from the current Makefile.am to texinfo.tex:

TEXINFO_TEX = ../doc/texinfo.tex

The option ‘no-texinfo.tex’ can be used to eliminate the requirement for texinfo.tex. Use of the variable TEXINFO_TEX is preferable, however, because that allows the dvi target to still work.

Automake generates an install-info target; some people apparently use this. By default, info pages are installed by ‘make install’. This can be prevented via the no-installinfo option.

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

Man pages are not currently considered to be source, because it is not uncommon for man pages to be automatically generated.

16.1 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 tags and TAGS targets 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

If you add filenames to ‘ETAGS_ARGS’, you will probably also want to set ‘TAGS_DEPENDENCIES’. The contents of this variable are added directly to the dependencies for the tags target.

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

16.2 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.

For instance, currently automake does not provide any Java support. If you wrote a macro to generate ‘.class’ files from ‘.java’ source files, you would also need to add these suffixes to the list:

SUFFIXES = .java .class