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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - thread-safety-analysis doesn't know about std::optional"
href="https://bugs.llvm.org/show_bug.cgi?id=38904">38904</a>
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<th>Summary</th>
<td>thread-safety-analysis doesn't know about std::optional
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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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>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>-New Bugs
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>lukasza@chromium.org
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Repro source code: <a href="https://godbolt.org/z/2XG89f">https://godbolt.org/z/2XG89f</a> (most important parts are
inlined below):
void test2() {
std::optional<AutoLock> maybe_autolock;
maybe_autolock.emplace(AutoLock(g_lock));
g_value += 1;
}
For real code where this bug would have mattered see
<a href="https://crbug.com/881875#c1">https://crbug.com/881875#c1</a> and
services/ws/public/cpp/gpu/context_provider_command_buffer.cc in Chromium which
calls base::Optional<base::AutoLock>::emplace(base::Lock&).
Unexpected error:
<source>:32:3: error: writing variable 'g_value' requires holding mutex
'g_lock' exclusively [-Werror,-Wthread-safety-analysis]
g_value += 1;
^</pre>
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