https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87106
--- Comment #23 from Arthur O'Dwyer <arthur.j.odwyer at gmail dot com> --- @Dan Stahlke: I believe https://stackoverflow.com/questions/47464819/uninitialized-copy-memcpy-memmove-optimization answers your question. Or, if it doesn't, then Marc or someone should consider posting an answer that's better than mine... and tell me whether I should delete my answer. :)