GCC - How to realign stack?

Question

I try to build an application which uses pthreads and __m128 SSE type. According to GCC manual, default stack alignment is 16 bytes. In order to use __m128, the requirement is t

Answer 1

Sorry to resurrect an old thread...

For those with a newer compiler than OP, OP mentions a -mstackrealign option, which lead me to __attribute__((force_align_arg_pointer)). If your function is being optimized to use SSE, but %ebp is misaligned, this will do the runtime fixes if required for you, transparently. I also found out that this is only an issue on i386. The x86_64 ABI guarantees the arguments are aligned to 16 bytes.

__attribute__((force_align_arg_pointer)) void i_crash_when_not_aligned_to_16_bytes() { ... }

Cool article for those who might want to learn more: http://wiki.osdev.org/System_V_ABI