How bad is “if (!this)” in a C++ member function?

Question

If I come across old code that does if (!this) return; in an app, how severe a risk is this? Is it a dangerous ticking time bomb that requires an immediate app-wide

Answer 1

In this case I'd suggest removing the NULL check from the member function and create a non-member function

CThingy* SafeLookup(CLookupThing *lookupThing) {
  if (lookupThing == NULL) {
    return NULL;
  } else {
    return lookupThing->Lookup();
  }
}

Then it should be easy enough to find every call to the Lookup member function and replace it with the safe non-member function.