[olliej]

That’s the point - it’s UB to go off the end of an array, or more generally to dereference a pointer outside of the bounds of the target object (yes, buffer+buffer_length is a valid pointer for the purpose of comparisons, but dereferencing it would be UB).

However in practice you can do this, and walk the stack to find the parameters or what have you, and then you’ve got a pointer to a parameter without the compiler being aware of it. But this is all explicitly UB, so it’s ok for the compiler to be unaware of it, and it’s free to do whatever codegen it wants given the assumption that UB can never happen.