1052738 - Breakpoint on the last line in an if block fires twice

Status: RESOLVED DUPLICATE of bug 1013219

(DevTools :: Debugger, defect)

Description

[Eddy Bruel [:ejpbruel]]

Steps to reproduce:
- In Nightly, open bug.html in the attachment
- Set a breakpoint on the following lines:
  - var a = 2;
  - var b = 3;
  - var c = 5
- Call the function f() in the console

Observed behavior:
- The breakpoint on the first two lines hits once, but the breakpoint on the last line hits twice (note how you have to resume twice).
- This only happens if you wrap the statements in an if-block, as I did here. If you remove the if-block the problem disappears.

Expected behavior:
- The breakpoint on the last line should hit only once as well.

Since the problem only occurs within an if-block, I suspect this has something to do with how we map source locations to breakpoint offsets.

Comment 1

[Eddy Bruel [:ejpbruel]]

Attachment: bug.html

Comment 2

[Girish Sharma [:Optimizer]]

I think this is similar:

When you go inside any loop, the execution first goes to the second last line of the loop block and then enter the loop....

Comment 3

[Eddy Bruel [:ejpbruel]]

I'm a bit surprised we still have so many issues with breakpoint offsets tbh. I thought we had pretty decent test coverage for that?

Comment 5

[Panos Astithas (he/him) [:past] (please ni?)]

The first pause in the "var c..." line happens in column 8, while the second one in column 9. I think we should inspect the source notes to get more data.

Comment 6

[Tom Tromey :tromey]

I believe this is another instance of bug #1013219.
The fix for that bug fixes this one as well.

Comment 7

[Tom Tromey :tromey]

(In reply to Tom Tromey :tromey from comment #6)
> I believe this is another instance of bug #1013219.
> The fix for that bug fixes this one as well.

I'm not sure why I didn't mark it as a dup then; doing so now.