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(autoconf.info)Macro Definitions

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Macro Definitions
=================

   Autoconf macros are defined using the `AC_DEFUN' macro, which is
similar to the `m4' builtin `define' macro.  In addition to defining a
macro, `AC_DEFUN' adds to it some code which is used to constrain the
order in which macros are called (Note: Prerequisite Macros).

   An Autoconf macro definition looks like this:

     AC_DEFUN(MACRO-NAME, [MACRO-BODY])

The square brackets here do not indicate optional text: they should
literally be present in the macro definition to avoid macro expansion
problems (Note: Quoting).  You can refer to any arguments passed to
the macro as `$1', `$2', etc.

   To introduce comments in `m4', use the `m4' builtin `dnl'; it causes
`m4' to discard the text through the next newline.  It is not needed
between macro definitions in `acsite.m4' and `aclocal.m4', because all
output is discarded until `AC_INIT' is called.

   Note: How to define new macros, for more
complete information on writing `m4' macros.