/// * `cb` is guaranteed to be called unless allocating `size` bytes on the stack causes a stack overflow, in which case the program will terminate.
/// * The data pointed to by `ptr` is guaranteed to be popped from the stack once this function returns (even in the case of a `longjmp`, but `panic!()` within the callback is still undefined behaviour).
// Never inline this, in case LTO inlines the call to `_alloca_trampoline`, we always want this function to pop the alloca'd memory.
// (NOTE: Test to see if this can ever happen. If it can't, the change this to `inline(always)` or remove the `inline` attribute
// (NOTE: Test to see if this can ever happen. If it can't, the change this to `inline(always)` or remove the `inline` attribute.)