Imagine the parameter is passed on the stack, I can take the address of a local variable (which in general forces it to be on the stack), I can then walk up the stack from that address to where the parameter is.
This is undefined behavior. Because it is UB that compiler is allowed to assume it cannot happen. Therefore I have the address of a parameter, and can pass that to a closure or whatever, and the parameter has escaped, but the compiler doesn't know.
More importantly by definition the compiler does not need to know, because a program that does that is no longer well defined.
This is undefined behavior. Because it is UB that compiler is allowed to assume it cannot happen. Therefore I have the address of a parameter, and can pass that to a closure or whatever, and the parameter has escaped, but the compiler doesn't know.
More importantly by definition the compiler does not need to know, because a program that does that is no longer well defined.