pthreads-win32 2.8.0, stack alignment, and SSE code

[Sébastien Kunz-Jacques <kunzjacq at yahoo dot fr>]

Hi,

I  encountered problems with SSE code compiled with recent mingw GCC 
(4.3.2, TDM release, http://www.tdragon.net/recentgcc/) and using 
pthreads 2.8.0. After inverstigation, crashes occured because the code 
was trying to read operands on the stack, assuming the stack was 16-byte 
aligned as is the case in the main thread (the main function aligns the 
stack and alignment is maintained during each function call).  I solved 
the issue with a very simple patch that uses some GCC wizardry to force 
stack realignment upon entry in a new thread:

--- ptw32_threadStart.c    Sun May 15 17:28:27 2005
+++ ptw32_threadStart.c    Mon Sep 29 21:28:16 2008
@@ -116,6 +116,9 @@

#endif

+#if defined(__GNUC__) && (__GNUC__ > 4 || __GNUC__ == 4 && 
__GNUC_MINOR__>1)
+__attribute__((force_align_arg_pointer))
+#endif
#if ! defined (__MINGW32__) || (defined (__MSVCRT__) && ! defined 
(__DMC__))
unsigned
  __stdcall


The attribute force_align_arg_pointer should be added to every function 
that is called with a stack with insufficient alignment; as far as I am 
concerned doing this for threadStart only solved my problems. Maybe this 
small patch could be added to the pthread code?