https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57503
--- Comment #18 from Marc Glisse <glisse at gcc dot gnu.org> --- (In reply to Georg-Johann Lay from comment #17) > Obervation that -fno-wrapv also leads to correct code, hence there is > somewhere a wrong assumption that signed overflow occurs (which doesn't). (you probably meant -fwrapv instead of -fno-wrapv?) Why do you say wrong? unsigned ab = a * b; in C, that means: unsigned ab = (int)a * (int)b; Since a is in [0, 255], so is (int)a. Multiplication may not overflow for a signed type, so (int)a*(int)b must be nonnegative. Converting it to long directly or through unsigned int is thus equivalent.
