https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64854 --- Comment #5 from Dominique d'Humieres <dominiq at lps dot ens.fr> --- Note that the error is detected if the code is compiled with -fsanitize=address. And IMO the right way to use the array in a 'contains' is a(:) (for which -fcheck=bounds works).