[Bug driver/71063] ICE: Segmentation fault with --help="^"

[ktkachov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71063

ktkachov at gcc dot gnu.org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |ktkachov at gcc dot gnu.org

--- Comment #2 from ktkachov at gcc dot gnu.org ---
The bug in opts.c is:

            if (* a == '^')
              {
                ++ a;
                pflags = & exclude_flags;
              }
            else
              pflags = & include_flags;

            comma = strchr (a, ',');
            if (comma == NULL)
              len = strlen (a);
            else
              len = comma - a;
            if (len == 0)
              {
                a = comma + 1;
                continue;
              }

For "^" a is advanced to "", 'comma' after the strchr is NULL, 'len' is
therefore 0 but then a is set to comma + 1, which is invalid and is dereference
at the top of the loop.