[Bug c++/107104] semantics of __builtin_constant_p within static_assert and return value

[yann at droneaud dot fr via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107104

Yann Droneaud <yann at droneaud dot fr> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |yann at droneaud dot fr

--- Comment #3 from Yann Droneaud <yann at droneaud dot fr> ---
I'm experiencing the same issue:

    #include <assert.h>

    void a(int v)
    {
        static_assert(__builtin_constant_p(v) && v == -1, "failure");
    }

GCC 13 and below complains:

    <source>: In function 'a':
    <source>:16:43: error: expression in static assertion is not constant
       16 |     static_assert(__builtin_constant_p(v) && v == -1, "failure");
          |                   ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~
    Compiler returned: 1


clang current trunk, eg above 15.0, seems to finally get it right:

    <source>:16:5: error: static assertion failed due to requirement
'__builtin_constant_p(v) && v == -1': failure
        static_assert(__builtin_constant_p(v) && v == -1, "failure");
        ^             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    /usr/include/assert.h:143:24: note: expanded from macro 'static_assert'
    # define static_assert _Static_assert
                           ^
    1 error generated.
    Compiler returned: 1

see https://godbolt.org/z/KKn6xTG8a