maybe calling a void function with no arguments did not change, but other things changed in various ways making it not stable.
What would be the point for the GCC team to even try to be compatible with a changing and non-documented ABI?
It wouldn't buy anything to just support how to mangle basic function, as they couldn't still be called. You either had to be fully compatible, or aren't.
And an ABI can be fairly complicated to implement. For example, in what register do we pass a class passed by value? It can change depending on whether some of its members are float, int or double, or whether it has copy constructor. You get anything wrong and the user suddenly get weird crashes that are going to be extremely hard to debug.
What would be the point for the GCC team to even try to be compatible with a changing and non-documented ABI?
It wouldn't buy anything to just support how to mangle basic function, as they couldn't still be called. You either had to be fully compatible, or aren't.
And an ABI can be fairly complicated to implement. For example, in what register do we pass a class passed by value? It can change depending on whether some of its members are float, int or double, or whether it has copy constructor. You get anything wrong and the user suddenly get weird crashes that are going to be extremely hard to debug.