https://issues.dlang.org/show_bug.cgi?id=14476
--- Comment #7 from Martin Nowak <c...@dawg.eu> --- This is a simple stack overflow. The unittest creates a thread with the minumum stack size of 4KiB and that thread crashes when calling pthread_attr_get_np. https://github.com/freebsd/freebsd/blob/01e375543f2cca888435d33af45404f00296ca0c/lib/libthr/thread/thr_attr.c#L139 The failure happens in a syscall. pthread_attr_get_np -> calloc -> syscall -> sbrk --