Giving labels as a argument in C/C++

Question

We have a label:

LABEL:
    //Do something.

and we have a function. We want pass LABEL as a argument to this function (otherwise we can't access labels in a function), and in some condition we want to jump this label. Is it possible?

I'm giving a example (pseudocode) for clarification:

GameMenu: //This part will be executed when program runs
//Go in a loop and continue until user press to [ENTER] key

while(Game.running) //Main loop for game
{
    Game.setKey(GameMenu, [ESCAPE]); //If user press to [ESCAPE] jump into GameMenu
    //And some other stuff for game
}

@iwin: We don't know if that "C/C++" language does allow this. Apparently OP thinks C and C++ are the same language. They are **not** — too honest for this site, Aug 04 '16 at 13:15
@Olaf I was thinking of goto which wouldn't let you jump to an external label in either language, didn't know about setjmp / longjmp. — flau, Aug 04 '16 at 13:18
@iwin: Well, it works in BASIC and Assembler for instance. Without proper context, there is no really good answer, but only speculation. VTC as unclear. `goto` has its uses, but chances are quite good OP's is none of them. — too honest for this site, Aug 04 '16 at 13:26

score 5 · Accepted Answer · answered Aug 04 '16 at 13:00

This sounds like an XY problem. You might want a state machine:

enum class State {
    menu,
    combat,
};

auto state = State::combat;
while (Game.running) {
    switch (state) {
    case State::combat:
        // Detect that Escape has been pressed (open menu).
        state = State::menu;
        break;

    case State::menu:
        // Detect that Escape has been pressed (close menu).
        state = State::combat;
        break;
    }
}

flau · Answer 2 · 2016-08-04T13:21:47.263

It seems like it may be worth refactoring your code to something similar:

void GameMenu() {
    // Show menu
}

void SomethingElse() {
    // Do something else
}

int main(int argc, char **argv) {

    (...)

    while(Game.running) {
        int key = GetKey();
        switch(key) {
        case ESCAPE:
            GameMenu();
            break;
        case OTHER_KEY:
            SomethingElse();
            break;
        }
    }
}

Sergio · Answer 3 · 2016-08-04T12:58:31.577

-1

You can use setjmp()/longjmp() to jump to some point in outer scope even to outer function. But note - jump target scope must be alive at the moment of jump.

edited Aug 04 '16 at 12:58

answered Aug 04 '16 at 12:57

Sergio

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Alive? What this means? – Ibrahim Ipek Aug 04 '16 at 12:58
3

[setjmp and longjmp are very dangerous in C++](http://stackoverflow.com/a/1376099/2491746). – Simple Aug 04 '16 at 13:05

Giving labels as a argument in C/C++

3 Answers3