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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Compiling at -O2 with atomics removes a null check resulting in a segfault at run time"
href="https://llvm.org/bugs/show_bug.cgi?id=25189">25189</a>
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<th>Summary</th>
<td>Compiling at -O2 with atomics removes a null check resulting in a segfault at run time
</td>
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<th>Product</th>
<td>new-bugs
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>new bugs
</td>
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>rtrieu@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>jfb@google.com, llvm-bugs@lists.llvm.org
</td>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=15081" name="attach_15081" title="Test case">attachment 15081</a> <a href="attachment.cgi?id=15081&action=edit" title="Test case">[details]</a></span>
Test case
After r216980, Clang is miscompiling code with atomics such that a null check
is removed causing a segfault shortly after.
Compiling the code with:
clang++ -O2 --std=c++11 test.cc
will produce a binary that segfaults in the function "DoStuff" on
"++data->counter;" even though two lines before it, a null check is performed
with "if (data == nullptr) return;". Compiling without -O2 will not produce a
segfault.</pre>
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