This is another good find. We haven't yet implemented the `!=` operator (or most of the binary operators).

Incidentally, you will notice that Xr0 rejects the program as is, which is correct (because of the double free). It can, however, accept code like the following:

  void
  foo(int a, int b)
  {
          int *p;
          p = malloc(1);
          if (a) {
                  if (!b) {
                          free(p);
                  }
          }
          if (b) {
                  free(p);
          }
          if (!a) {
                  if (!b) {
                          free(p);
                  }
          }
  }

I say "can" because we only have this working on a development branch [0], and there are still some issues we're resolving on this, hopefully by next week.

[0]: https://github.com/xr0-org/xr0/tree/fix/nested-branching