Bug 130634 – Remove Dead Stores from editing directory

• Component: WebCore Misc.
• Status: RESOLVED FIXED

[Jinwoo Song]

Remove Dead Stores from editing directory which assigning a value to a variable and never reading that value.

[Jinwoo Song]

Created attachment 227536 [details]
Patch

[Darin Adler]

Comment on attachment 227536 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=227536&action=review

> Source/WebCore/editing/CompositeEditCommand.cpp:-843
> -            gapEnd = std::min(gapEnd, end);

I suspect the dead store here indicates a bug. I think that gapLen needs to be recomputed. Instead of removing this line of code, we should add a line of code:

    gapLen = gapEnd - gapStart;

But of course, we also need to construct a test case to demonstrate that the code is incorrect, which could be difficult.

[Darin Adler]

(In reply to comment #0)
> Remove Dead Stores from editing directory which assigning a value to a variable and never reading that value.

I assume you are finding these with a tool or compiler warning. Could you specify what compiler this is and what warning option, or what tool?

[Jinwoo Song]

Comment on attachment 227536 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=227536&action=review

>> Source/WebCore/editing/CompositeEditCommand.cpp:-843
>> -            gapEnd = std::min(gapEnd, end);
> 
> I suspect the dead store here indicates a bug. I think that gapLen needs to be recomputed. Instead of removing this line of code, we should add a line of code:
> 
>     gapLen = gapEnd - gapStart;
> 
> But of course, we also need to construct a test case to demonstrate that the code is incorrect, which could be difficult.

Then I'll remain this line and make an another bug to follow up this issue.

[Jinwoo Song]

(In reply to comment #3)
> (In reply to comment #0)
> > Remove Dead Stores from editing directory which assigning a value to a variable and never reading that value.
> 
> I assume you are finding these with a tool or compiler warning. Could you specify what compiler this is and what warning option, or what tool?

I just run a static analyzer built into Xcode (on Mac).  :)

[Jinwoo Song]

Created attachment 227622 [details]
Patch

Do not remove dead store in CompositeEditCommand.cpp according to Darin's comment. I'll make another bug for tracking this one.

[Jinwoo Song]

Comment on attachment 227536 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=227536&action=review

>>> Source/WebCore/editing/CompositeEditCommand.cpp:-843
>>> -            gapEnd = std::min(gapEnd, end);
>> 
>> I suspect the dead store here indicates a bug. I think that gapLen needs to be recomputed. Instead of removing this line of code, we should add a line of code:
>> 
>>     gapLen = gapEnd - gapStart;
>> 
>> But of course, we also need to construct a test case to demonstrate that the code is incorrect, which could be difficult.
> 
> Then I'll remain this line and make an another bug to follow up this issue.

Created a bug, https://bugs.webkit.org/show_bug.cgi?id=130658

[WebKit Commit Bot]

Comment on attachment 227622 [details]
Patch

Clearing flags on attachment: 227622

Committed r166150: <http://trac.webkit.org/changeset/166150>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.