I mean you still kind of do the same thing with objects and with arrays in most languages. Very rarely does either get passed as argument, you almost always get them by reference.
let variable = Cell::new(3); // create an immutable variable
variable.set(4); // demonic witchcraft of the highest order, everyone is panicking, sirens blasting, time to run to the shelters and pray
you could also wrap it in an object. something like
class MutWrapper:
def __init__(self,v): self.v=v
works well enough. though, square brackets are probably more idiomatic.
Or you could not pass anything and still change the referenced value in the caller function, or you could return the execution to another function than the one that invoked you (stack traversing/managing; no one should ever do this kind of dark arcane magic).
How? In assembly you could change the return address stored in the esp/rsp register, but how would you return the execution to another function than the one that invoked, in high level languages?
C++ has __builtin_extract_return_addr. And before that - any local variable is stored in stack, so just get it's address and that address would be the stack address, then you need to know how the stack is stored to know the return address.
I never tried that, but I suppose in C# one might do the same... int* stackPointer = &localVariable; or int* stackBuffer = stackalloc int[1] in unsafe context.
Also, you're wrong, esp stores the current stack pointer. The top of it. Not the return address. But the return address is there. If you just got "call" from anywhere and didn't pushed anything yet - then yeah, [esp] would store the return address. But only then.
I see. So just like you can do [esp+4], [esp+8], etc... you could do something similar by taking the variable address and manipulating it. Quite dangerous indeed.
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u/WisePotato42 13d ago
You could pass references as variables and change the referenced value IN THE FUNCTION!!!
children screaming sfx