> Having done this for a dozen of experiments/toys I fully agree with most of the post, would be nice if the the addition of must_tail attribute could be reliable across the big 3 compilers, but it's not something that can be relied on (luckily Clang seems to be fairly reliable on Windows these days).
replyThis may be a stupid question, but if the function must tail, that's just a jump, no? Why not use goto?
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.
replyNote 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...
reply(though it is fine if GC can only happen inside a function call and the call takes the shadow stack as an argument)
> ... [pointers] need to be clumped into one array ...
replyYou could put each stack frame into a struct, and have the first field be a pointer to a const static stack-map data structure or function that enumerates the pointers within the frame.
BTW, the passed pointer to this struct could also be used to implement access to the calling function's variables, for when you have nested functions and closures.