Unskilled programmers changing code

So my coworker may have found a bug in one of our big jewels-of-the-company core libraries. We send off the bug report along with a short sample program that demonstrates the bug; to make a long bug short, it tries a certain sequence of operations in a specific order and fails (the library call returns a bizarre error status) half-way through.

We get back the message: "we couldn't reproduce the effects you mentioned; when we compiled the code here it coredumps at the first attempted operation".
( Longer story about debugging someone else's changes )

---

And now a small rant about C and the equivalence of a null pointer and an uncasted-to-anything 0.( C gripe )