https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67685
Andrew Sutton <andrew.n.sutton at gmail dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |andrew.n.sutton at gmail dot com --- Comment #2 from Andrew Sutton <andrew.n.sutton at gmail dot com> --- Quickly investigating. In tsubst_requires_expr, we add to the local specialization stack, which means that any local variables or parameters referenced within the requires-expression will not be visible, which ultimately causes undefined behavior in tsubst_copy.