Hi, I don't know if this is known, but since I wasted half a day on it, I thought I could avoid the pain for someone else: do not build numpy with -fomit-frame-pointer with mingw (windows), it will crash. I don't know if this just cannot be used, if this is a mingw bug, or something on our side. But you do not want to look for a bug caused by using this option. cheers, David