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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:
Of course, it supports the Autoconf common subset of options:
As an extension of m4, it includes the following options:
AC_DIAGNOSE
, for a comprehensive list of categories. Special
values include:
Warnings about `syntax' are enabled by default, and the environment variable WARNINGS, a comma separated list of categories, is honored. `autom4te -W category' actually behaves as if you had run:
autom4te --warnings=syntax,$WARNINGS,category
For example, if you want to disable defaults and WARNINGS of autom4te, but enable the warnings about obsolete constructs, you would use -W none,obsolete.
autom4te displays a back trace for errors, but not for
warnings; if you want them, just pass -W error.
.m4f
is
replaced by file.m4
. This helps tracing the macros which
are executed only when the files are frozen, typically
m4_define
. For instance, running:
autom4te --melt 1.m4 2.m4f 3.m4 4.m4f input.m4
is roughly equivalent to running:
m4 1.m4 2.m4 3.m4 4.m4 input.m4
while
autom4te 1.m4 2.m4f 3.m4 4.m4f input.m4
is equivalent to:
m4 --reload-state=4.m4f input.m4
autom4te 1.m4 2.m4 3.m4 --freeze --output=3.m4f
corresponds to
m4 1.m4 2.m4 3.m4 --freeze-state=3.m4f
As another additional feature over m4, autom4te caches its results. GNU M4 is able to produce a regular output and traces at the same time. Traces are heavily used in the GNU Build System: autoheader uses them to build config.h.in, autoreconf to determine what GNU Build System components are used, automake to “parse” configure.ac etc. To avoid recomputation, traces are cached while performing regular expansion, and conversely. This cache is (actually, the caches are) stored in the directory autom4te.cache. It can safely be removed at any moment (especially if for some reason autom4te considers it trashed).
Because traces are so important to the GNU Build System, autom4te provides high level tracing features as compared to M4, and helps exploiting the cache:
The format is a regular string, with newlines if desired, and several special escape codes. It defaults to `$f:$l:$n:$%'. It can use the following special escapes:
The escape `$%' produces single-line trace outputs (unless you put newlines in the `separator'), while `$@' and `$*' do not.
See autoconf Invocation, for examples of trace uses.
Finally, autom4te introduces the concept of Autom4te libraries. They consists in a powerful yet extremely simple feature: sets of combined command line arguments:
M4sugar
M4sh
Autotest
Autoconf-without-aclocal-m4
Autoconf
Autoconf-without-aclocal-m4
and
additionally reads aclocal.m4.
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 --warnings syntax 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.