[Bug 43127] Multiple 64-bit applications crash with stack overflow errors when Wine is compiled with GCC 7.x (set_context_reg in ntdll/ signal_x86_64.c assumes Xmm registers are aligned)

https://bugs.winehq.org/show_bug.cgi?id=43127

--- Comment #6 from Sebastian Lackner  ---
Created attachment 58336
  --> https://bugs.winehq.org/attachment.cgi?id=58336
ntdll: Do not cast unaligned pointer to M128A in set_context_reg.

Please give the attached draft patch a try. Not sure if its sufficient to fix
the bug, but at least the generated GCC output looks much better (still uses
Xmm registers for efficiency, but no longer makes any assumption that they are
properly aligned).