Re: strncasecmp dcl

[Paul Eggert]

> From: Werner LEMBERG <address@hidden>
> Date: Wed, 20 Jun 2001 22:11:53 +0200 (CEST)
> 
> How can this be fixed properly?

One way to fix it would be to follow the lead of AC_HEADER_TIME and
define an AC_HEADER_STRING that defines STRING_WITH_STRINGS if you can
include both <sys/time.h> and <time.h>.  However, I've always thought
this method to be clumsy, as it clutters up the code.

Since <string.h> clearly dominates <strings.h>, how about the following
method instead:

* Modify _AC_INCLUDES_DEFAULT_REQUIREMENTS so that it does not
  define HAVE_STRINGS_H if the two include files are incompatible.

* Modify the default includes to use the following pattern:

     #if HAVE_STRING_H
     # if !STDC_HEADERS && HAVE_MEMORY_H
     #  include <memory.h>
     # endif
     # include <string.h>
     #endif
     #if HAVE_STRINGS_H
     # include <strings.h>
     #endif

* (This is the tricky part.)  Modify AC_CHECK_HEADER to use
  AC_INCLUDES_DEFAULT before including the header in question.  That
  way, if string.h and strings.h are incompatible, HAVE_STRINGS_H
  won't be defined; this is because the code checks string.h before
  checking for strings.h.  Extend AC_CHECK_HEADER to accept a new,
  fourth argument specifying the default includes, just as
  AC_CHECK_DECL does.

The advantage of the last step is that it will cause autoconf to
always check for header incompatibility.  If done right, this would
render AC_HEADER_TIME obsolete.