[Bug c/67824] New: constexpr char* compare operations not constexpr, but char[] operations ARE

["erich.keane at intel dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67824

            Bug ID: 67824
           Summary: constexpr char* compare operations not constexpr, but
                    char[] operations ARE
           Product: gcc
           Version: 5.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: erich.keane at intel dot com
  Target Milestone: ---

The below code reproduces this bug, found in 4.9.2, but also reproduced in
5.2.1

Version results for both:

g++ (GCC) 4.9.2 20150212 (Red Hat 4.9.2-6)
Copyright (C) 2014 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

g++ (SUSE Linux) 5.2.1 20150721 [gcc-5-branch revision 226027]
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

This code compiles correctly on clang++ 3.5 and 3.6.1.  

it seems that the 'root' variable below gets treated correctly, yet the root2,
despite being a valid string as well, doesn't allow pointer operations on it. 
This is painful, since it breaks constexpr iterators on constexpr const char*
items.



static constexpr const char root[] = "1234";
static constexpr const char* root2 = "1234";

int main()
{
    static_assert(root < root + 1, "This works");
    static_assert(root2 < root2 + 1, "This fails");
}