[systemd-devel] [PATCH] architecture: fix building for big-endian PowerPC with gcc

[Dan Horák]

On Fri, 11 Jul 2014 15:27:56 +0200
Lennart Poettering <lennart at poettering.net> wrote:

> On Fri, 11.07.14 15:04, Michael Olbrich (m.olbrich at pengutronix.de)
> wrote:
> 
> > gcc does not define WORDS_BIGENDIAN for big-endian PowerPC. It
> > defines __BIG_ENDIAN__ instead. So also check for __BIG_ENDIAN__ to
> > determine if the system is big-endian.
> 
> Hmm, the sources currently use three different ways to detect
> endianess:
> 
> 1) WORDS_BIGENDIAN (which appears to be an autoconf thing actually,
>    enabled via AC_C_BIGENDIAN, which we never call currently)
> 2) __BTYE_ORDER == __BIG_ENDIAN which appears to be be defined in
>    endian.h always by glibc
> 3) __BIG_ENDIAN__ appears to be quite common too? gcc thing?
> 
> Also this:
> 
> http://sourceforge.net/p/predef/wiki/Endianness/
> 
> We should probably stick to one of these things. Probably #2 or #3...
> 
> I can't find any normative documentation about these things. Given
> that the #2 is at least unconditional part of glibc, I'd say to
> convert everything to that. Would that work for you on ppc-be too?

Jakub explained us endianity checks with GCC in
https://bugzilla.redhat.com/show_bug.cgi?id=962091#c48


		Dan