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Issue 784768 link

Starred by 1 user
Status: WontFix
Owner:
kozy@chromium.org
Closed: Dec 2017
Components:
EstimatedDays: ----
NextAction: ----
OS: Linux
Pri: 2
Type: Bug



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Debugger appear to stop at incorrect positions

Project Member Reported by jensj@google.com, Nov 14 2017 
UserAgent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/62.0.3202.75 Safari/537.36

Steps to reproduce the problem:
Example code:
```
<html>
  <head>
    <script>
baz();
function baz() {
  print(foo(), bar());
  return 42;
}
function foo() {
  return "foo";
}

function bar() {
  return 1 + 2 + 3 + 4;
}

function print(a, b) {
  console.log(a);
  console.log(b);
}
    </script>
  </head>
  <body>
    <h1>Hello, stepping</h1>
  </body>
</html>
```

1. Set a breakpoint on line 6 (first line in "baz")
2. Reload or whatnot so it breaks. It appears to have stopped at "print".
3. Stepping (F11) goes into "foo". Stepping further it goes back into "baz" and correctly stops on "bar".

What is the expected behavior?
Breaking on 'foo' in line 6 (i.e. line 6 column 9).

What went wrong?
It seems that the first break is always at the first code of the line, even if it is actually about to execute something else. In this case it is about to call "foo" (not "print") so it should be pointing to "foo" (line 6 column 9).

Did this work before? N/A 

Chrome version: 62.0.3202.75  Channel: stable
OS Version: 
Flash Version:

Comment 1 by l...@chromium.org, Nov 14 2017

Owner: kozy@chromium.org
Status: Assigned (was: Unconfirmed)
Thanks for the report.  kozy@ will know whether this is intended behavior or not.

Comment 2 by kozy@chromium.org, Dec 4 2017

Status: WontFix (was: Assigned)
JavaScript is a little trickier. At the given expression JavaScript tries to call getter print on global object first if it is defined. So we break at this position to guarantee that we do not skip this getter call.
Try following example:
<html>
  <head>
    <script>
Object.defineProperty(window, 'log', {get: () => print});
baz();
function baz() {
  log(foo(), bar());
  return 42;
}
function foo() {
  return "foo";
}

function bar() {
  return 1 + 2 + 3 + 4;
}

function print(a, b) {
  console.log(a);
  console.log(b);
}
    </script>
  </head>
  <body>
    <h1>Hello, stepping</h1>
  </body>
</html>
►

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