Only if the fix involves breaking the old semantics entirely. It's possible in some cases to support old semantics in a safe way at the cost of performance, or

Only if the fix involves breaking the old semantics entirely. It's possible in some cases to support old semantics in a safe way at the cost of performance, or in the case that it's not you can disable that call in such a way that the program aborts if it is called, thus indicating that the user should relink that program. This is why integration projects such as Linux distributions are hard, and useful.