https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79876
--- Comment #13 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Seems libgomp has a bug that without {,G}OMP_STACKSIZE and with OMP_DISPLAY_ENV it displays random (uninitialized) value for the stack size, so I need to test something like: 2017-03-30 Jakub Jelinek <ja...@redhat.com> * env.c (initialize_env): Initialize stacksize to 0. --- libgomp/env.c.jj 2017-01-01 12:45:52.000000000 +0100 +++ libgomp/env.c 2017-03-30 16:07:29.800247913 +0200 @@ -1187,7 +1187,7 @@ handle_omp_display_env (unsigned long st static void __attribute__((constructor)) initialize_env (void) { - unsigned long thread_limit_var, stacksize; + unsigned long thread_limit_var, stacksize = 0; int wait_policy; /* Do a compile time check that mkomp_h.pl did good job. */ If we figure out what Darwin versions have so insanely low defaults and agree on some more reasonable one (1M or 2M?), then we could change this to something like: stacksize = GOMP_DEFAULT_STACKSIZE; and later on where it parse_stacksize add || stacksize to the condition last, then define GOMP_DEFAULT_STACKSIZE 0 by default and let some config/darwin/ header override it.