[Python-Dev] How to test for stuff like fsync?

["Martin v. Löwis"]

Guido van Rossum wrote:

> Is there really no function prototype in the system headers for
> fsync() on those systems, or don't we see it because we're using
> feature selection macros (isn't that the right term?) that hide it?

I really can't answer that for all systems that lost fsync; I only
know about a single one. I earlier said it was Redhat, but I recalled
that incorrectly; it was "a 2-year-old Linux box running slackware"
(no idea what slackware version). It is also unclear what specific
version of the C library headers where installed on the system; the
compiler is gcc 2.7.2.

On that system, fsync is only available if __USE_BSD is defined,
see python.org/sf/800710. So on the surface, it looks like a feature
selection macro which we fail to define (_BSD_SOURCE), instead of
a feature selection macro that we do define. OTOH, it might be
that the definition of _XOPEN_SOURCE on that system would cause
__USE_BSD not to be defined - I don't have a copy of features.h
of the particular system.

In recent glibc versions, fsync is declared if either __USE_BSD or 
__USE_XOPEN is defined.

Regards,
Martin