Stack alignment is not guaranteed by ABI and GCC doesn't enforce it in function prolog. There is already similar problem in gfx/cairo/libpixman/src/pixman.c. It's interesting that we don't hit it on Linux GCC builds (although its ABI also doesn't enforce alignment). The attached patch fixes the problem by adding __force_align_arg_pointer__ attribute.

Comment on attachment 505397 [details] [diff] [review] fix v1.0 Look simple enough, but I don't think I'm the right person to review this.

(In reply to comment #0) > It's interesting that we don't hit it on Linux GCC builds (although its ABI > also doesn't enforce alignment). http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40838 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38496 suggest that Linux ABI does require 16-bit stack alignment.

Comment on attachment 505397 [details] [diff] [review] fix v1.0 r=dbaron, but in the future, please post patches with 8 lines of context, and preferably with a useful From: header and commit message.

Sorry for the patch format, I will change that in the future. http://hg.mozilla.org/mozilla-central/rev/fa9559ec420a