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6.2 Other things Automake recognizes

Every time Automake is run it calls Autoconf to trace This way it can recognize the use of certain macros and tailor the generated appropriately. Currently recognized macros and their effects are:

Automake will ensure that config.guess and config.sub exist. Also, the Makefile variables build_triplet, host_triplet and target_triplet are introduced. See Getting the Canonical System Type.
Automake will look for various helper scripts, such as install-sh, in the directory named in this macro invocation. (The full list of scripts is: ar-lib, config.guess, config.sub, depcomp, elisp-comp, compile, install-sh,, mdate-sh, missing, mkinstalldirs, py-compile, test-driver, texinfo.tex, ylwrap.) Not all scripts are always searched for; some scripts will only be sought if the generated requires them.

If AC_CONFIG_AUX_DIR is not given, the scripts are looked for in their standard locations. For mdate-sh, texinfo.tex, and ylwrap, the standard location is the source directory corresponding to the current For the rest, the standard location is the first one of ., .., or ../.. (relative to the top source directory) that provides any one of the helper scripts. See Finding `configure' Input.

Required files from AC_CONFIG_AUX_DIR are automatically distributed, even if there is no in this directory.

Automake will require the sources file declared with AC_LIBSOURCE (see below) in the directory specified by this macro.
Automake will generate rules to rebuild these headers. Older versions of Automake required the use of AM_CONFIG_HEADER (see Macros); this is no longer the case.

As with AC_CONFIG_FILES (see Requirements), parts of the specification using shell variables will be ignored as far as cleaning, distributing, and rebuilding is concerned.

Automake will generate rules to remove configure generated links on ‘make distclean’ and to distribute named source files as part of ‘make dist’.

As for AC_CONFIG_FILES (see Requirements), parts of the specification using shell variables will be ignored as far as cleaning and distributing is concerned. (There are no rebuild rules for links.)

Automake will automatically distribute any file listed in AC_LIBSOURCE or AC_LIBSOURCES.

Note that the AC_LIBOBJ macro calls AC_LIBSOURCE. So if an Autoconf macro is documented to call ‘AC_LIBOBJ([file])’, then file.c will be distributed automatically by Automake. This encompasses many macros like AC_FUNC_ALLOCA, AC_FUNC_MEMCMP, AC_REPLACE_FUNCS, and others.

By the way, direct assignments to LIBOBJS are no longer supported. You should always use AC_LIBOBJ for this purpose. See AC_LIBOBJ vs. LIBOBJS.

This is required if any libraries are built in the package. See Particular Program Checks.
This is required if any C++ source is included. See Particular Program Checks.
This is required if any Objective C source is included. See Particular Program Checks.
This is required if any Objective C++ source is included. See Particular Program Checks.
This is required if any Fortran 77 source is included. See Particular Program Checks.
This is required for programs and shared libraries that are a mixture of languages that include Fortran 77 (see Mixing Fortran 77 With C and C++). See Autoconf macros supplied with Automake.
Automake will add the flags computed by AC_FC_SRCEXT to compilation of files with the respective source extension (see Fortran Compiler Characteristics).
This is required if any Fortran 90/95 source is included. This macro is distributed with Autoconf version 2.58 and later. See Particular Program Checks.
Automake will turn on processing for libtool (see Introduction).
If a Yacc source file is seen, then you must either use this macro or define the variable YACC in The former is preferred (see Particular Program Checks).
If a Lex source file is seen, then this macro must be used. See Particular Program Checks.
For each AC_REQUIRE_AUX_FILE([file]), automake will ensure that file exists in the aux directory, and will complain otherwise. It will also automatically distribute the file. This macro should be used by third-party Autoconf macros that require some supporting files in the aux directory specified with AC_CONFIG_AUX_DIR above. See Finding configure Input.
The first argument is automatically defined as a variable in each generated, unless AM_SUBST_NOTMAKE is also used for this variable. See Setting Output Variables.

For every substituted variable var, automake will add a line var = value to each file. Many Autoconf macros invoke AC_SUBST to set output variables this way, e.g., AC_PATH_XTRA defines X_CFLAGS and X_LIBS. Thus, you can access these variables as $(X_CFLAGS) and $(X_LIBS) in any if AC_PATH_XTRA is called.

This introduces an Automake conditional (see Conditionals).
This macro allows automake to detect subsequent access within to a conditional previously introduced with AM_CONDITIONAL, thus enabling conditional AC_CONFIG_FILES (see Usage of Conditionals).
This macro is required for packages that 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.
This macro specifies that the intl/ subdirectory is to be built, even if the AM_GNU_GETTEXT macro was invoked with a first argument of ‘external’.
This macro adds an --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, unless default-mode is ‘enable’. This macro defines the MAINTAINER_MODE conditional, which you can use in your own See maintainer-mode.
Prevent Automake from defining a variable var, even if it is substituted by config.status. Normally, Automake defines a make variable for each configure substitution, i.e., for each AC_SUBST([var]). This macro prevents that definition from Automake. If AC_SUBST has not been called for this variable, then AM_SUBST_NOTMAKE has no effects. Preventing variable definitions may be useful for substitution of multi-line values, where var = @value@ might yield unintended results.
Files included by using this macro will be detected by Automake and automatically distributed. They will also appear as dependencies in Makefile rules.

m4_include is seldom used by authors, but can appear in aclocal.m4 when aclocal detects that some required macros come from files local to your package (as opposed to macros installed in a system-wide directory, see aclocal Invocation).