G_MEM_ALIGN may not be correct

[David Mosberger <davidm napali hpl hp com>]

Hi,

I hope it's appropriate to discuss glib issues on this list.  If not,
my apologies (please direct me to a more appropriate place in that
case).

I noticed that gmem.h declares:

#if GLIB_SIZEOF_VOID_P > GLIB_SIZEOF_LONG
#  define G_MEM_ALIGN   GLIB_SIZEOF_VOID_P
#else   /* GLIB_SIZEOF_VOID_P <= GLIB_SIZEOF_LONG */
#  define G_MEM_ALIGN   GLIB_SIZEOF_LONG
#endif  /* GLIB_SIZEOF_VOID_P <= GLIB_SIZEOF_LONG */

(I verified that this code is still in the CVS-version of glib.)

Unfortunately, this isn't sufficient for ia64 (and perhaps other
platforms) because on that platform, malloc-like routines need to
guarantee 16-byte alignment due to the fact that "long double" typed
variables need to be 16-byte aligned.

There are several ways to solve this problem.  For example, we could
mirror the glibc malloc, which uses 2*sizeof(size_t) alignment, or we
could mirror what the GNU obstack implementation does (that would
require config-time checking of alignment, though).  Of course, we
could also just check for #ifdef __ia64, though that seems fragile and
too platform-specific.

Does anybody have a preference for how to get this fixed?

Thanks,

	--david