[Bug c++/89757] accepts returning with reference to temporary in constant expression

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89757

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |msebor at gcc dot gnu.org
             Blocks|                            |55004

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
In the test case below with pointers rather than references the first static
assertion also isn't rejected despite being undefined, and despite the
-Wreturn-local-addr.  (Clang fails the first assertion because unlike GCC it
doesn't fold the return address to null.)

$ cat t.C && gcc -S -Wall t.C
constexpr int* f (int i)
{
  return &i;
}

static_assert (nullptr == f (123));
static_assert (nullptr != f (123));
t.C: In function ‘constexpr int* f(int)’:
t.C:3:10: warning: address of local variable ‘i’ returned [-Wreturn-local-addr]
    3 |   return &i;
      |          ^~
t.C:1:23: note: declared here
    1 | constexpr int* f (int i)
      |                   ~~~~^
t.C: At global scope:
t.C:7:24: error: static assertion failed
    7 | static_assert (nullptr != f (123));
      |                ~~~~~~~~^~~~~~~~~~


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55004
[Bug 55004] [meta-bug] constexpr issues