Related to shadow stacks, I've had trouble convincing the C optimizer that no one else is aliasing my heap-allocated helper stacks. Supposedly there ought to be a way to tell it using restrict annotations, but those are quite fiddly: only work for function parameters, and can be dusmissed for many reasons. Does anyone know of a compiler that successfully used restrict pointers in their generated code? I'd love to be pointed towards something that works.
Note that declaring no aliasing is probably unsafe for concurrent or moving garbage collectors, as then the C compiler can conveniently "forget" to either store or load values to the shadow stack at some points...
(though it is fine if GC can only happen inside a function call and the call takes the shadow stack as an argument)