[Bug sanitizer/81598] -fsanitize=enum does not detect range violation

["marxin at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81598

Martin Liška <marxin at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2017-08-03
                 CC|                            |mpolacek at gcc dot gnu.org
     Ever confirmed|0                           |1
           Severity|normal                      |enhancement

--- Comment #3 from Martin Liška <marxin at gcc dot gnu.org> ---
I believe we can instrument more in order to catch more situations:

enum values
{
  A = 1000,
  B = 30,
  C = 100
};

enum values g;

int main(int argc, char **argv)
{
  enum values x = (enum values)argc;
  if (x == 12345)
    return 1;

  return g;

  switch (x)
  {
    case A:
      return 1;
    case C:
      return 2;
    case 123:
      return 3;
  }
}

In this case, CFG is based on values that are undefined. As I've been working
on research of switch statement, I noticed that it's very common that switch
covers all possibly values of an enumeral type. Having that, we can instrument
default label with some UBSAN call.