https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100224
Richard Biener <rguenth at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |INVALID Status|UNCONFIRMED |RESOLVED --- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> --- You are accessing 'double' via a pointer to uint64_t * here: k = *((uint64_t*)data); that violates type based aliasing rules. You can use -fno-strict-aliasing to work around your bug or use typedef uint64_t aliasing_uint64_t __attribute__((may_alias)); k = *((aliasing_uint64_t*)data);