When `for` loop has a label at beginning, `break` does not work correctly

[wch]

Consider the following code

for (var i=0; i<4; i++)
label: {
  console.log(i);
  if (i === 1) {
    console.log("break");
    break;
  }
}

When I run this code in Safari, Firefox, Chrome, or V8's d8 console, they print out:

0
1
break

However, with qjs, it prints:

0
1
break
2
3

For context, I'm encountering this problem with some code generated from compiling Dart Sass to JS: sass/dart-sass#2212

[wch]

An even simpler version:

for (var i=0; i<4; i++)
label: {
  console.log(i);
  break;
}

[chqrlie]

This is certainly a bug.
It is unusual to label some thing that is not a loop statement, which might explain why it went unnoticed until now.
Thank you for reporting this.

[andrjohns]

Just wanted to flag that this bug is affecting more use-cases now that the js_of_ocaml Ocaml->JS compiler has moved to heavy use of labels and break statements for control flow

If it doesn't seem like too tricky a problem, I'd be happy to have a try - would just need to be pointed towards the right place to start. Thanks!

[chqrlie]

@andrjohns: I shall take a look this week.

[bnoordhuis]

fwiw, I just fixed this in quickjs-ng/quickjs@66732e7

[bellard]

applied