[Bug c++/118951] __FILE__ inserts the filename as array, __builtin_FILE as pointer

[m.cencora at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118951

m.cencora at gmail dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |m.cencora at gmail dot com

--- Comment #2 from m.cencora at gmail dot com ---
> Also there's nothing like an array return value for functions in C or C++?

Yes, but we can use C++20 CTAD for template parameters to workaround this:

#include <cstddef>

constexpr const auto& my_builtin_FILE()
{
    return __FILE__;
}

template <std::size_t N>
struct static_string
{
    constexpr static_string(const char* s)
    {
        auto it = &buf[0];
        while (*s != '\0')
        {
            *it++ = *s++;
        }
        *it = '\0';
    }

    char buf[N];
};

template <std::size_t N>
static_string(const char (&str)[N]) -> static_string<N>;

template <class T, static_string File = my_builtin_FILE(), auto Line =
__builtin_LINE()>
struct strong_alias{/*...*/};

using Celsius = strong_alias<unsigned>;

void test(Celsius)
{}

int main()
{

}