[Bug c/121479] The return value of __builtin_constant_p() is inconsistent at different optimization levels

[jakub at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121479

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
That differs between C and C++, in C++ x in that case is a constant expression
and __builtin_constant_p will be certainly true, in C it is not a constant
expression and it is solely an extension and optimization when it is treated as
a constant expression.