Re: [PATCH] Calling AC_USE_SYSTEM_EXTENSIONS through several of its aliases should not issue a cryptic warning

[Eric Blake]

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According to Ralf Wildenhues on 10/10/2008 6:47 AM:
>>> * lib/autoconf/specific.m4 (AC_USE_SYSTEM_EXTENSIONS): Move
>>> the body to ...
>>> (_AC_USE_SYSTEM_EXTENSIONS): ... this new macro and require it
>>> from the original and ...
>>> (AC_GNU_SOURCE, AC_AIX, AC_MINIX): ... from all of these.
>> I think it looks sound; it ensures that the code is expanded only once,
>> instead of once for each variant spelling.  If you wouldn't mind, can you
>> also write up a NEWS item before applying?
> 
> Doesn't it break
> 
>   AC_DEFUN([FOO], 
>   [
>     CC=$some_override...
>     AC_PROG_CC
>     AC_USE_SYSTEM_EXTENSIONS
>   ])
> 
> and wasn't that part of an earlier bug report?

AC_DEFUN([FOO],
[AC_PROG_CC
 AC_USE_SYSTEM_EXTENSIONS
])

was already broken.  The earlier bug report was about:

AC_DEFUN([FOO],
[AC_PROG_CC
 AC_GNU_SOURCE
])

since it used to just define a variable, but now triggers code that needs
the compiler.  But it probably still needs some thought about which cases
we want to support, and definitely test cases.  Maybe we need to go lower
level and use m4_provide_if instead of m4_require to avoid the warnings
about duplicate expansion.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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