https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121479
Jakub Jelinek <jakub at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED CC| |jakub at gcc dot gnu.org Resolution|--- |INVALID --- Comment #1 from Jakub Jelinek <jakub at gcc dot gnu.org> --- That is not a bug, that is exactly how __builtin_constant_p is designed and documented: "The function returns the integer 1 if the argument is known to be a compile-time constant and 0 if it is not known to be a compile-time constant. A return of 0 does not indicate that the value is _not_ a constant, but merely that GCC cannot prove it is a constant with the specified value of the '-O' option."