This effects gcc-4.8.1 and 4.8.2 (at least), on both mingw32 and mingw64, the following program segfaults:
__float128 a = expq(2.0Q);
Mingw gcc-4.7.x and Linux are obviously both fine.
Please provide at least a backtrace with debugging symbols available.
This seems to be a bug in mingw-w64.
See here: http://sourceforge.net/p/mingw-w64/bugs/368/
This was apparently a bug in mingw itself, and was fixed a while back. I'm closing this report.
Please reopen it, with added info (such as backtrace), if you still see this problem with latest mingw.