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<base href="https://bugs.freedesktop.org/" />
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<th>Priority</th>
<td>medium
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<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - [Patch] Fix for crasher in quartz backend"
href="https://bugs.freedesktop.org/show_bug.cgi?id=62885">62885</a>
</td>
</tr>
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<th>Assignee</th>
<td>vladimir@pobox.com
</td>
</tr>
<tr>
<th>Summary</th>
<td>[Patch] Fix for crasher in quartz backend
</td>
</tr>
<tr>
<th>QA Contact</th>
<td>cairo-bugs@cairographics.org
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr>
<tr>
<th>OS</th>
<td>All
</td>
</tr>
<tr>
<th>Reporter</th>
<td>m.j.hutchinson@gmail.com
</td>
</tr>
<tr>
<th>Hardware</th>
<td>Other
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Version</th>
<td>1.12.14
</td>
</tr>
<tr>
<th>Component</th>
<td>quartz backend
</td>
</tr>
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<th>Product</th>
<td>cairo
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=77176" name="attach_77176" title="Fixes the crash.">attachment 77176</a> <a href="attachment.cgi?id=77176&action=edit" title="Fixes the crash.">[details]</a></span>
Fixes the crash.
There is currently a crash in the Quartz backend when performing certain
operations. it's relatively easy to trigger, and actually happens 7 times in
the test suite. It appears to have been a known problem for almost a year:
<a href="http://lists.freedesktop.org/archives/cairo/2012-April/022950.html">http://lists.freedesktop.org/archives/cairo/2012-April/022950.html</a>
When the problem is triggered, CoreGraphics prints several error messages
similar to the following:
context_reclaim: invalid context 0x1da71050
context_finalize: invalid context 0x1da71050
Then there is a hard crash:
malloc: *** error for object 0x24485004: incorrect
checksum for freed object - object was probably modified after being freed.
[snip]
4 libsystem_c.dylib 0x9889b4ec abort + 168
5 libsystem_c.dylib 0x98885227 szone_error + 443
6 libsystem_c.dylib 0x98886482 free_list_checksum_botch
+ 50
7 libsystem_c.dylib 0x98886564
tiny_free_list_remove_ptr + 112
8 libsystem_c.dylib 0x9887ff11 szone_free + 993
9 CoreFoundation 0x954cad38
__CFAllocatorSystemDeallocate + 24
10 CoreFoundation 0x954cad18 CFAllocatorDeallocate +
232
11 CoreFoundation 0x954caa7a CFRelease + 2042
12 libcairo.2.dylib 0x06615d25
_cairo_quartz_teardown_state + 117
13 libcairo.2.dylib 0x06616fba _cairo_quartz_cg_fill +
378
14 libcairo.2.dylib 0x0656318b _cairo_compositor_fill +
251
15 libcairo.2.dylib 0x06618375
_cairo_quartz_surface_fill + 165
16 libcairo.2.dylib 0x065d42eb _cairo_surface_fill +
315
17 libcairo.2.dylib 0x0656fbdc _cairo_gstate_fill + 812
18 libcairo.2.dylib 0x06567e8c
_cairo_default_context_fill + 44
19 libcairo.2.dylib 0x0655a69b cairo_fill + 43
I'm pretty sure the problem is that _cairo_quartz_teardown_state is releasing
something it doesn't own. It does:
CGContextRelease (state->cgDrawContext);
But, the only places that this field is assigned, it comes from a *Get*
function and is therefore not owned by the caller, and is not ref'fed either:
state->cgDrawContext = CGLayerGetContext (state->layer);
Since the state also keeps a reference to the layer that owns the context,
ref'ing it would be redundant. Instead, I just removed the superfluous
CGContextRelease.
The attaches patch fixes the 7 crashes in the test suite, and the crashes in
the application I'm working on.</pre>
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