g++ cross distro compilation problem

[Nick Stokes]

On Fri, Jan 21, 2011 at 4:16 AM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> On 21 January 2011 02:03, Nick Stokes wrote:
>>>
>>> But unfortunately this didn't work either. The reason is subtle (and
>>> elusive!): On CentOS (where gcc is built) the GCC features.h header is
>>> defining __USE_XOPEN2K, and not __USE_XOPEN2K8  conditioned on
>>> _XOPEN_SOURCE (or _POSIX_C_SOURCE) being defined.   But on the
>>> front-end SUSE, the /usr/include/locale.h is expecting __USE_XOPEN2K8,
>>> hence fails.
>
> By "GCC features.h header" do you mean one under the GCC installation
> tree in /opt, or /usr/include/features.h?  If the former, that
> explains the problem - you have a fixinclude'd features.h created on
> the old system, which has a glibc that predates POSIX 2008, so
> _GNU_SOURCE doesn't define __USE_XOPEN2K8 (as I think it would on a
> newer glibc)
>


Yes, exactly. CentOS isn't really "cutting edge" in updates..


>> I guess I can sweep under the rug for now by defining __USE_XOPEN2K8.
>> Incidentally, I need to make this transparent for users. Is it
>> possible to add such "custom" definitions to gcc at configure time (or
>> is there some other way to accomplish this)?
>
> http://gcc.gnu.org/onlinedocs/gcc/Spec-Files.html
>
> Or you can provide a wrapper script which invokes the actual gcc
> driver with the additional flags you need.
>
> Rather than defining __USE_XOPEN2K8 (which is definitely not meant to
> be defined/undefined by users) I would consider modifying the
> features.h file so that _GNU_SOURCE sets __XOPEN28K.  You could try
> building the same GCC on a login machine, and compare the features.h
> from that build (if it has one, otherwise just use
> /usr/include/features.h)
>

This sounds best.

Thanks a lot Jonathan!