in reply to
Re: Debugging XS modules under Strawberry perl
in thread Debugging XS modules under Strawberry perl
Thanks, that was enough to get near the place where the error was happening and from there trace the program with WinDbg.
The actual problem is that gcc generates MOVDQA (Move Aligned Double Quadword) instructions to load the int128 integers from memory to the mmx registers, and those require 16-byte alignment for their memory arguments. Perl own malloc implementation only guarantees 8-byte alignment on Windows, so eventually, the module crashes.