Minor problem with configure (2.4.4)

[MRAB]

sndive at gmail.com wrote:
> configure expands
>   AC_DEFINE(_POSIX_C_SOURCE, 200112L, Define to activate features from
> IEEE Stds 1003.1-2001)
>
> to
>
> #define _POSIX_C_SOURCE 200112L
>
> that causes problems because _POSIX_C_SOURCE is defined by system
> headers and I get hideous
> warnings during compilation.
>
> I tried to fix it by adding AC_UNDEFINE(_POSIX_C_SOURCE);
> before AC_DEFINE but autoconf 2.59 won't take it:
>
> configure.in:273: error: possibly undefined macro: AC_UNDEFINE
>       If this token and others are legitimate, please use
> m4_pattern_allow.
>       See the Autoconf documentation.
>
> Ideas?

It looks like AC_DEFINE is #define'd but AC_UNDEFINE isn't.

Try:

#undef _POSIX_C_SOURCE

instead.