http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50616
--- Comment #10 from Kai Tietz <ktietz at gcc dot gnu.org> 2012-02-19 16:31:32 UTC --- Yes, not all msvcrt versions are supporting %ll width modifier. Modern versions of it (as 64-bit versions) are supporting it, but older (and still pretty common on 32-bit OSes) don't. Therefore it is for native Windows apps more compatible to use here instead %I64. As Andrew mentioned we might should use here instead PRIx64 for output of 64-bit integer-scalars. Any patch in this direction would be welcome for me.
