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(autoconf.info)Obsoleting Macros

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Obsoleting Macros
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   Configuration and portability technology has evolved over the years.
Often better ways of solving a particular problem are developed, or
ad-hoc approaches are systematized.  This process has occurred in many
parts of Autoconf.  One result is that some of the macros are now
considered "obsolete"; they still work, but are no longer considered
the best thing to do, hence they should be replaced with more modern
macros.  Ideally, `autoupdate' should substitute the old macro calls
with their modern implementation.

   Autoconf provides a simple means to obsolete a macro.

 - Macro: AU_DEFUN (OLD-MACRO, IMPLEMENTATION, [MESSAGE])
     Define OLD-MACRO as IMPLEMENTATION.  The only difference with
     `AC_DEFUN' is that the user will be warned that OLD-MACRO is now
     obsolete.

     If she then uses `autoupdate', the call to OLD-MACRO will be
     replaced by the modern IMPLEMENTATION.  The additional MESSAGE is
     then printed.