[Bug c++/57248] string parameter to constexpr functions

["paolo.carlini at oracle dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57248

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |paolo.carlini at oracle dot com

--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> ---
It would be nice if Daniel could have another look to this, because his reduced
testcase in Comment #3 doesn't work anymore as a reproducer, is simply accepted
by eg, the released 4.9.0.

Also, I note that all the compilers I have at hand reject the original testcase
and also, eg:

constexpr bool strmatch(const char *s1, const char *s2)
{
  return (*s1==*s2) ? 
            (*s1=='\0') ? 
               true
               : strmatch(s1+1, s2+1) 
            : false;
}

template <unsigned N>
constexpr int index(const char (&array)[N])
{
  return strmatch(array, "m0") ? 0 : -1;
}

template <int N>
constexpr int get() { return 1; }

template<unsigned N>
constexpr int extract(const char (&array)[N]) {
  return get<index(array)>();
}

int main(void)
{
  constexpr int i = strmatch("m0", "m0");  // OK
  constexpr int j = index("m0");  // OK
  constexpr int k = extract("m0"); // Not OK
}