I am using Arch Linux and after some recent updates, the 32 bit build of XLib (/usr/lib32/libX11.so.6.4.0) now requires a page (16 bytes) alignment of the stack or else crashes with SIGSEGV inside the library (movaps [esp+0x20], xmm4)
While the immediate reason for the crash is clear, however, some questions arise:
Is this a bug, some build options problem, or permanent ABI changes that breaks the backward compatibility?