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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - UBSan reports false positives on unaligned memory accesses on MS ABI"
href="https://llvm.org/bugs/show_bug.cgi?id=28754">28754</a>
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<th>Summary</th>
<td>UBSan reports false positives on unaligned memory accesses on MS ABI
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>-New Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>resistor@mac.com
</td>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>Microsoft explicitly documents unaligned memory accesses on scalar types to be
allowed under their ABI, though natural alignment is still recommended for
performance reasons. UBSan still reports errors on unaligned scalar accesses,
leading to false positives on code that is compliant with the MS ABI.
Note that Microsoft's document does still require natural alignment for members
of unions and aggregates.
MS alignment documentation for scalar types:
<a href="https://msdn.microsoft.com/en-us/library/94z15h2c.aspx">https://msdn.microsoft.com/en-us/library/94z15h2c.aspx</a>
MS alignment documentation for unions and aggregates:
<a href="https://msdn.microsoft.com/en-us/library/9dbwhz68.aspx">https://msdn.microsoft.com/en-us/library/9dbwhz68.aspx</a></pre>
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