[quietbritishjim]

That's not the same: you have to cooperate in the game, so if you have a library that uses it internally and you call one of its functions in the normal way then it will still just return as usual. So it still provides the usual guarantees of function calling, even if you don't want it to.

(It also doesn't allow you to jump into the middle of a function, or to take more than a finite number of steps unless you're using a compiler with guaranteed tail call elimination.)

[quietbritishjim]

Just to add:

If you want to have proper jump-anywhere goto in C, you can do it a lot more simply than that: just put all your code in one function and use regular goto. If you want to use only structured programming constructions, use a while(true) loop with a switch statement inside.

The fact remains that code outside that function can still call it safely in the normal way.