On Fri, 3 Feb 2012, DJ Delorie wrote: > > Jan Kara <jack@xxxxxxx> writes: > > we've spotted the following mismatch between what kernel folks expect > > from a compiler and what GCC really does, resulting in memory corruption on > > some architectures. Consider the following structure: > > struct x { > > long a; > > unsigned int b1; > > unsigned int b2:1; > > }; > > If this structure were volatile, you could try > -fstrict-volatile-bitfields, which forces GCC to use the C type to > define the access width, instead of doing whatever it thinks is optimal. > > Note: that flag is enabled by default for some targets already, most > notably ARM. Note that -fstrict-volatile-bitfields does not work for volatile struct S { int i : 1; char c; } s; int main() { s.i = 1; s.c = 2; } where it accesses s.i using SImode. -fstrict-volatile-bitfields falls foul of all the games bitfield layout plays and the irrelevantness of the declared bitfield type (but maybe the ARM ABI exactly specifies it that way). So no, I would not recommend -fstrict-volatile-bitfields. Richard. -- To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html