You know this, but being explicit helps the casual reader: The "elimination" in "tail call elimination" refers to the "elimination" of the call frame. In lang

You know this, but being explicit helps the casual reader: The "elimination" in "tail call elimination" refers to the "elimination" of the call frame. In languages like C each call pushes a frame to the call stack. When the called procedure is done, execution returns to the site of the call. In a tail call there is no work to done, so the frame is now removed and execution continues where the previous frame points. But ... if we simply never omit the call frame, then executation then exectuation automatically returns to the parent frame. The spec talks about allowing an "unbounded number of active tail calls". In an implementation with frames, it means tail calls can't just keep pushing frames. Seen in isolation "tail call elimination" doesn't seem like a big deal, but combined with "real macros" (structural, scope-respecting macros) it is possible to implement control structures as a user without worrying about stack overflow.