https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123915
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> --- >From https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1005.pdf : When the state of the FX_ACCUM_OVERFLOW pragma is SAT, the overflow behavior on _Accum types is saturation; otherwise, overflow on _Accum types has undefined behavior. The default state for the FX_FRACT_OVERFLOW and FX_ACCUM_OVERFLOW pragmas is DEFAULT. Note GCC does not implement these pragma and that is mentioned here: https://gcc.gnu.org/onlinedocs/gcc/Fixed-Point.html
