I used to work on lower level stuff a place with a large C++ codebase designed by a bunch of C guys. We had tight memory requirements, so a custom operator new (not nothrow) was supplied; but exceptions were also disabled, so the supplier of operator new couldn't throw in their implementation.

So that's how it was, and the code base was littered with lots of little checks on what new expressions were returning, things like:

  int *p = new int[1024];
  if (!p) return SOME_ERROR;
  doSomething(*p);

Of course, the C++ standard says that operator new will never return null (it's supposed to throw if it fails). So the compiler sees this code and says "hey, that if (!p) check isn't necessary.." and so none of those little checks gets emitted. Sure enough, it happens that the operator new returns null now and then because everyone is on a tight memory budget, but instead of catching it and returning an error, the code just goes on to crash.