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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - -Wpessimizing-move false positive for return value of statement expression"
href="https://llvm.org/bugs/show_bug.cgi?id=25640">25640</a>
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<th>Summary</th>
<td>-Wpessimizing-move false positive for return value of statement expression
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>3.7
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Frontend
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>sugak@fb.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The following code generates a -Wpessimizing-move violation:
```
#include <memory>
#include <utility>
class C {};
void f() {
auto c = ({auto c1 = std::make_unique<C>(); std::move(c1);});
}
1.cpp:5:47: error: moving a local object in a return statement prevents copy
elision [-Werror,-Wpessimizing-move]
auto c = ({auto c1 = std::make_unique<C>(); std::move(c1);});
^
1.cpp:5:47: note: remove std::move call here
auto c = ({auto c1 = std::make_unique<C>(); std::move(c1);});
^~~~~~~~~~ ~
```
When `std::move` is removed, it becomes a syntax error:
```
1.cpp:5:47: error: call to deleted constructor of 'std::unique_ptr<C,
std::default_delete<C> >'
auto c = ({auto c1 = std::make_unique<C>(); c1;});
^~
.../unique_ptr.h:356:7: note: 'unique_ptr' has been explicitly marked deleted
here
unique_ptr(const unique_ptr&) = delete;
^
1 error generated.
```
clang --version
clang version 3.8.0 (trunk 251726)
Target: x86_64-unknown-linux-gnu
Thread model: posix</pre>
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