On Thu, Jan 13, 2011 at 10:57:15PM +0100, Joerg Sonnenberger wrote: > On Thu, Jan 13, 2011 at 12:19:00PM -0500, Ryan Stone wrote: > > I've been trying to get an application compiled with gcc 4.5.1 running > > on FreeBSD 8.1, but it's been crashing during startup with a SIGBUS. > > It turns out that the problem is that gcc is issuing SSE > > instructions(in my case, a movdqa) that assume that the stack will be > > aligned to a 16-byte boundary. It seems that Linux/i386 guarantees > > this, and I worry that gcc has extended this assumption to all i386 > > architectures. I'm assuming that FreeBSD doesn't make any such > > promises based on the fact that I'm getting crashes. > > FreeBSD follows the original SYSV ABI. Linux at some point silently > decided to redefine the ABI to fit their mindset. I think you want to > use a combination of -mpreferred-stack-boundary=4 and > -mincoming-stack-boundary=2.
I think gcc [*] requires 16-byte alignment. Also, it follows the policy of not changing the stack alignment through the calls. What you see is a plain bug in FreeBSD, when a developer (me) tried to adopt to newer ABI but failed. * Might be not gcc in our tree, but definitely newer gcc releases.
pgpFmrQkAdFNW.pgp
Description: PGP signature
