8.2.1 Invoking autom4te

The command line arguments are modeled after M4’s:

autom4te options files

where the files are directly passed to m4. By default, GNU M4 is found during configuration, but the environment variable M4 can be set to tell autom4te where to look. In addition to the regular expansion, it handles the replacement of the quadrigraphs (see Quadrigraphs), and of ‘__oline__’, the current line in the output. It supports an extended syntax for the files:

file.m4f

This file is an M4 frozen file. Note that all the previous files are ignored. See the --melt option for the rationale.

file?

If found in the library path, the file is included for expansion, otherwise it is ignored instead of triggering a failure.

Of course, it supports the Autoconf common subset of options:

--help

-h

Print a summary of the command line options and exit.

--version

-V

Print the version number of Autoconf and exit.

--verbose

-v

Report processing steps.

--debug

-d

Don’t remove the temporary files and be even more verbose.

--include=dir

-I dir

Also look for input files in dir. Multiple invocations accumulate.

--output=file

-o file

Save output (script or trace) to file. The file - stands for the standard output.

As an extension of m4, it includes the following options:

--warnings=category[,category...]

-Wcategory[,category...]

Enable or disable warnings related to each category. See m4_warn, for a comprehensive list of categories. Special values include:

‘all’

Enable all categories of warnings.

‘none’

Disable all categories of warnings.

‘error’

Treat all warnings as errors.

‘no-category’

Disable warnings falling into category.

The enviroment variable WARNINGS may also be set to a comma-separated list of warning categories to enable or disable. It is interpreted exactly the same way as the argument of --warnings, but unknown categories are silently ignored. The command line takes precedence; for instance, if WARNINGS is set to obsolete, but -Wnone is given on the command line, no warnings will be issued.

Some categories of warnings are on by default. Again, for details see m4_warn.

--melt

-M

Do not use frozen files. Any argument file.m4f is replaced by file.m4. This helps tracing the macros which are executed only when the files are frozen, typically m4_define. For instance, running:

autom4te --melt 1.m4 2.m4f 3.m4 4.m4f input.m4

is roughly equivalent to running:

m4 1.m4 2.m4 3.m4 4.m4 input.m4

while

autom4te 1.m4 2.m4f 3.m4 4.m4f input.m4

is equivalent to:

m4 --reload-state=4.m4f input.m4

--freeze

-F

Produce a frozen state file. autom4te freezing is stricter than M4’s: it must produce no warnings, and no output other than empty lines (a line with white space is not empty) and comments (starting with ‘#’). Unlike m4’s similarly-named option, this option takes no argument:

autom4te 1.m4 2.m4 3.m4 --freeze --output=3.m4f

corresponds to

m4 1.m4 2.m4 3.m4 --freeze-state=3.m4f

--mode=octal-mode

-m octal-mode

Set the mode of the non-traces output to octal-mode; by default ‘0666’.

As another additional feature over m4, autom4te caches its results. GNU M4 is able to produce a regular output and traces at the same time. Traces are heavily used in the GNU Build System: autoheader uses them to build config.h.in, autoreconf to determine what GNU Build System components are used, automake to “parse” configure.ac etc. To avoid recomputation, traces are cached while performing regular expansion, and conversely. This cache is (actually, the caches are) stored in the directory autom4te.cache. It can safely be removed at any moment (especially if for some reason autom4te considers it trashed).

--cache=directory

-C directory

Specify the name of the directory where the result should be cached. Passing an empty value disables caching. Be sure to pass a relative file name, as for the time being, global caches are not supported.

--no-cache

Don’t cache the results.

--force

-f

If a cache is used, consider it obsolete (but update it anyway).

Because traces are so important to the GNU Build System, autom4te provides high level tracing features as compared to M4, and helps exploiting the cache:

--trace=macro[:format]

-t macro[:format]

Trace the invocations of macro according to the format. Multiple --trace arguments can be used to list several macros. Multiple --trace arguments for a single macro are not cumulative; instead, you should just make format as long as needed.

The format is a regular string, with newlines if desired, and several special escape codes. It defaults to ‘$f:$l:$n:$%’. It can use the following special escapes:

‘$$’

The character ‘$’.

‘$f’

The file name from which macro is called.

‘$l’

The line number from which macro is called.

‘$d’

The depth of the macro call. This is an M4 technical detail that you probably don’t want to know about.

‘$n’

The name of the macro.

‘$num’

The numth argument of the call to macro.

‘$@’

‘$sep@’

‘${separator}@’

All the arguments passed to macro, separated by the character sep or the string separator (‘,’ by default). Each argument is quoted, i.e., enclosed in a pair of square brackets.

‘$*’

‘$sep*’

‘${separator}*’

As above, but the arguments are not quoted.

‘$%’

‘$sep%’

‘${separator}%’

As above, but the arguments are not quoted, all new line characters in the arguments are smashed, and the default separator is ‘:’.

The escape ‘$%’ produces single-line trace outputs (unless you put newlines in the ‘separator’), while ‘$@’ and ‘$*’ do not.

See autoconf Invocation, for examples of trace uses.

--preselect=macro

-p macro

Cache the traces of macro, but do not enable traces. This is especially important to save CPU cycles in the future. For instance, when invoked, autoconf pre-selects all the macros that autoheader, automake, autoreconf, etc., trace, so that running m4 is not needed to trace them: the cache suffices. This results in a huge speed-up.

Finally, autom4te introduces the concept of Autom4te libraries. They consists in a powerful yet extremely simple feature: sets of combined command line arguments:

--language=language

-l language

Use the language Autom4te library. Current languages include:

M4sugar

create M4sugar output.

M4sh

create M4sh executable shell scripts.

Autotest

create Autotest executable test suites.

Autoconf-without-aclocal-m4

create Autoconf executable configure scripts without reading aclocal.m4.

Autoconf

create Autoconf executable configure scripts. This language inherits all the characteristics of Autoconf-without-aclocal-m4 and additionally reads aclocal.m4.

--prepend-include=dir

-B dir

Prepend directory dir to the search path. This is used to include the language-specific files before any third-party macros.

As an example, if Autoconf is installed in its default location, /usr/local, the command ‘autom4te -l m4sugar foo.m4’ is strictly equivalent to the command:

autom4te --prepend-include /usr/local/share/autoconf \
  m4sugar/m4sugar.m4f foo.m4

Recursive expansion applies here: the command ‘autom4te -l m4sh foo.m4’ is the same as ‘autom4te --language M4sugar m4sugar/m4sh.m4f foo.m4’, i.e.:

autom4te --prepend-include /usr/local/share/autoconf \
  m4sugar/m4sugar.m4f m4sugar/m4sh.m4f --mode 777 foo.m4

The definition of the languages is stored in autom4te.cfg.