1607871 - [jsdbg2] onStep handlers can fire for non-debuggee frames

Status: NEW

(Core :: JavaScript Engine, defect, P3)

Description

[Jim Blandy :jimb]

A frame's onStep handler can fire even when the frame's global is not a debuggee, and the frame is dead:

var g = newGlobal({ newCompartment: true });
g.eval(`
  function f() {
    print("hi");
  }
`);

var dbg1 = new Debugger(g);
var dbg2 = new Debugger(g);
dbg1.other = dbg2;
dbg2.other = dbg1;

dbg1.onEnterFrame = dbg2.onEnterFrame = function(frame) {
  let other = this.other;
  frame.onStep = function() {
    print(this.callee.name);
    other.removeDebuggee(g);
  };
};

g.f();

This should print f once and then exit, but instead it prints:

f
/home/jimb/moz/onstep.js:16:5 Error: Debugger.Frame is not on stack or suspended
Stack:
  f@/home/jimb/moz/onstep.js line 2 > eval:3:5
  @/home/jimb/moz/onstep.js:21:3