Date: Thu, 13 Jan 2011 22:57:15 +0100 From: Joerg Sonnenberger <joerg@britannica.bec.de> To: freebsd-hackers@freebsd.org, FreeBSD Hackers <hackers@freebsd.org> Subject: Re: What does the FreeBSD/i386 ABI say about stack alignment? Message-ID: <20110113215713.GB5278@britannica.bec.de> In-Reply-To: <AANLkTikrsHUO3M%2Bfvo0kO%2B3dPq8OHu5L2zBf3fa3jL2x@mail.gmail.com> References: <AANLkTikrsHUO3M%2Bfvo0kO%2B3dPq8OHu5L2zBf3fa3jL2x@mail.gmail.com>
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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. Joerg
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