Re: installable gnulib library

[Eric Blake]

On 10/10/2010 08:19 PM, Gary V. Vaughan wrote:
> > The common way to get rid of these warnings is to insert an invocation of
> > gl_USE_SYSTEM_EXTENSIONS at the appropriate place in configure.ac.
>
> Seems like a kludge to me.  Either the AC_{RUN,COMPILE}_IFELSE using modules
> should AC_REQUIRE_ONCE([gl_USE_SYSTEM_EXTENSIONS]) themselves, or AC_{RUN,
> COMPILE}_IFELSE should invoke the require rather than the warning, no?  And
> if that doesn't work, then AC_REQUIRE is not outputting macro expansions in
> the right order.
>
> What's the difference between AC_USE_SYSTEM_EXTENSIONS and gl_USE_SYSTEM_
> EXTENSIONS?  The warnings seem to indicate that adding AC_REQUIRE([AC_
> USE_SYSTEM_EXTENSIONS]) to AC_{RUN,COMPILE}_IFELSE is the right solution.

AC_RUN_IFELSE must NOT require AC_USE_SYSTEM_EXTENSIONS - the whole 
point of having them as separate macros is that it MUST be possible to 
write a project that conforms to strict C89 and does not require the use 
of AC_USE_SYSTEM_EXTENSIONS.  Rather, what needs to be fixed is the 
notion that _if_ you use AC_USE_SYSTEM_EXTENSIONS, then its use must 
precede AC_RUN_IFELSE.  And right now, there is a known bug in AC_BEFORE 
(which is the mechanism for enforcing this order), which when that bug 
is fixed, starts failing the AC_USE_SYSTEM_EXTENSIONS testsuite in 
autoconf.  Therefore, there is probably an upstream bug in autoconf's 
AC_USE_SYSTEM_EXTENSIONS that is not generating correctly ordered output.

--
Eric Blake   address@hidden    +1-801-349-2682
Libvirt virtualization library http://libvirt.org