[Bug c++/77298] New: -Wnonnull-compare only emitted for code which is invoked

[wipedout at yandex dot ru]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77298

            Bug ID: 77298
           Summary: -Wnonnull-compare only emitted for code which is
                    invoked
           Product: gcc
           Version: 6.1.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: wipedout at yandex dot ru
  Target Milestone: ---

On http://gcc.godbolt.org/ I select gcc 6.1 and specify -O3 -Wall

The code is:
struct CHandle {
  int handle;
  int GetHandle() const
  {
    if (this != 0) //[-Wnonnull-compare] emitted
      return handle;
    return 0;
  }
};
int main()
{
  CHandle* h = new CHandle();
  return h->GetHandle();
}

Initially [-Wnonnull-compare] is emitted where "this" is checked for null. Now
I change main() to this:

int main()
{
  CHandle* h = new CHandle();
  return 0;//h->GetHandle();
}

and the warning is no longer emitted. The code is compiled and it's known at
compile time that there's a check of "this" against null yet not warning.