https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55561
--- Comment #51 from Jakub Jelinek <jakub at gcc dot gnu.org> --- (In reply to Roland Schulz from comment #50) > I must say I don't know how the internals work. But I assume that reductions > are implemented in libgomp (I know they are in iomp). Thus for any code > which uses OpenMP reduce statements, libgomp would touch user data. Your assumption is wrong, reductions are not handled in libgomp, but in the code emitted by the compiler.