If it doesn't control both then TCO is impossible, because the stack will grow with each recursive step, as it's just performing a normal call.
replyHave your mind blown: https://godbolt.org/z/xnn3PPxvW
replyExtremely specific example is uncompelling.
replyIt is a simple counterexample to your incorrect statement.
replyIt's possible for calling conventions where the callee is responsible for stack cleanup before return.
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