[webkit-dev] WebKit bug in Dashboard widget?

[Maciej Stachowiak]

On Jul 9, 2005, at 8:24 PM, Ben Kazez wrote:

> Hi everyone,
>
> I'm working on a Dashboard widget with a multi-threaded Cocoa  
> plugin. The plugin seems to be working just fine, but I'm getting  
> an occasional (frequent but inconsistent) crash that appears to  
> indicate a bug in WebKit:
>
> ======================================================
> Exception:  EXC_BAD_ACCESS (0x0001)
> Codes:      KERN_PROTECTION_FAILURE (0x0002) at 0x00000018
>
> Thread 0 Crashed:
> 0   com.apple.WebCore              0x95c4a734 khtml::inlineWidth 
> (khtml::RenderObject*, bool, bool) + 152
> 1   com.apple.WebCore              0x95c48b98  
> khtml::RenderBlock::findNextLineBreak(khtml::BidiIterator&,  
> khtml::BidiState&) + 3548
> 2   com.apple.WebCore              0x95c46dbc  
> khtml::RenderBlock::layoutInlineChildren(bool) + 1980
> 3   com.apple.WebCore              0x95c435d4  
> khtml::RenderBlock::layoutBlock(bool) + 692
> 4   com.apple.WebCore              0x95c4a49c  
> khtml::RenderBlock::layoutPositionedObjects(bool) + 172
> 5   com.apple.WebCore              0x95c43930  
> khtml::RenderBlock::layoutBlock(bool) + 1552
> 6   com.apple.WebCore              0x95c4409c  
> khtml::RenderBlock::layoutBlockChildren(bool) + 696
> 7   com.apple.WebCore              0x95c435ec  
> khtml::RenderBlock::layoutBlock(bool) + 716
> 8   com.apple.WebCore              0x95c40524  
> khtml::RenderCanvas::layout() + 252
> 9   com.apple.WebCore              0x95c3fe08 KHTMLView::layout() +  
> 792
> 10  com.apple.WebCore              0x95c52518 -[WebCoreBridge  
> forceLayoutAdjustingViewSize:] + 56
> 11  com.apple.WebKit               0x959ce11c -[WebHTMLView  
> layoutToMinimumPageWidth:maximumPageWidth:adjustingViewSize:] + 228
> 12  com.apple.WebKit               0x959e1328 -[WebHTMLView 
> (WebPrivate) _web_layoutIfNeededRecursive] + 36
> 13  com.apple.WebKit               0x959cb8c0 -[WebHTMLView 
> (WebPrivate) _propagateDirtyRectsToOpaqueAncestors] + 72
> ...
> ======================================================
>
> The crash is preceded by incorrect width of displayed divs,  
> disappearing elements, or both. Does this seem to you to be a  
> WebKit bug, or could there be a problem with my code?

It's hard to tell. This bug sounds likely to be some kind of memory  
trasher, so it may be that something is corrupting memory. Is your  
plugin calling WebKit APIs from multiple threads? WebKit is not  
threadsafe so that is one possible cause.

Can you reproduce it with just a plain web page with no plugin? If  
so, it would definitely be a WebKit bug.

Regards,
Maciej