1108153 - Stepping through an if (false) { ... } block makes it look like the last statement of the block is executed

Status: RESOLVED DUPLICATE of bug 1003554

(DevTools :: Debugger, defect)

Description

[Peter Kehl]

Attachment: test.xul

User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:33.0) Gecko/20100101 Firefox/33.0
Build ID: 20141113113219

Steps to reproduce:

Use Browser TooBox to run an .xul or similar. Have Javascript:

if( false ) {
   some code one one or more separate lines....
}

See the attached test.xul.

Debug that part of the code from line 'if(false) {' by Stepping over (F10).


Actual results:

After you press button Step Over (F10) at line 'if(false) {', debugger moves to the last line of the if() {...} block. The current execution line indicator  looks as if it were about to execute that last line of the code. This may be less confusing when you have multiple lines in the {...} block, but it's highly confusing if there is just one line.

Then press Step Over (F10) again. The current execution line indicator doesn't move. It moves only on the next Step Over (F10). Again, confusing.


Expected results:

It should go to the line where there's the next command after the enclosing '}'.

This may be remotely related to issue #1051632.

Comment 1

[Eddy Bruel [:ejpbruel]]

This bug looks similar to though not quite the same as bug 1052738.

Comment 2

[Tom Tromey :tromey]

This is fixed by the patch for bug 1003554.
The underlying problem is that a compiler-generated instruction
is given a misleading line number.