449766 - Variable value remains 'undefined' when stopped in a debugger before initialization

Status: RESOLVED WORKSFORME

(Other Applications Graveyard :: Venkman JS Debugger, defect)

Description

[Max Stepanov]

User-Agent:       Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.0.1) Gecko/2008070206 Firefox/3.0.1
Build Identifier: 2008070206

When script execution is interrupted by JSD (breakpoint or debugger keyword), a value of variable differs from uninterrupted case.

Reproducible: Always

Steps to Reproduce:
1. Open attached mootools_sample.html
2. Enable Firebug (1.2.0 or beta)
3. Set a breakpoint at line 15 (var index = selector.selectedIndex)
4. Press 'Test' button, Firebug suspends execution; see 'index' value as'undefined'.
5. Continue execution, see 'undefined' alert box.
---
Repeat #1, #2 as above
3. Set breakpoint at line 14 (var selector = $("ab")).
Repeat #4, #5 above; see '0' as value.

Comment 1

[Max Stepanov]

Attachment: Test case to reproduce

Comment 2

[Caio Tiago Oliveira (asrail)]

There is this warning related, but I don't know if this is the cause:
WARNING: Positioned frame that does not handle positioned kids; looking further up the parent chain: file /home/asrail/mozbuilds/hg.mozilla.org/comm-central/mozilla/layout/base/nsCSSFrameConstructor.cpp, line 7635

Comment 3

[Caio Tiago Oliveira (asrail)]

Confirmed on trunk, linux.

Comment 4

[Karsten Düsterloh]

This is filed under Venkman, but I fail to see the problem with current (SeaMonkey) trunk Venkman...

And besides, setting breakpoint on "var index = selector.selectedIndex" will of course result in index being undefined, because the break will happen before the initialization...

Comment 5

[Philipp Kewisch [:Fallen][📱📆]]

IIUC, then without a debugger attachd, the alert() call outputs '0', but when you attach the debugger on line 15 and then continue, the alert() call outputs 'undefined'.

Comment 6

[Karsten Düsterloh]

(In reply to comment #5)
> IIUC, then without a debugger attachd, the alert() call outputs '0', but when
> you attach the debugger on line 15 and then continue, the alert() call outputs
> 'undefined'.

That's my understanding as well, but I don't see this, using Venkman trunk with a SeaMonkey Linux trunk build...

Comment 7

[Max Stepanov]

Just tested with Firefox 3.6.13 and Firebug 1.6.2 - does not an issue anymore.