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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Unclear warning -Wreturn-std-move"
href="https://bugs.llvm.org/show_bug.cgi?id=45872">45872</a>
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<th>Summary</th>
<td>Unclear warning -Wreturn-std-move
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Windows NT
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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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>jvapen@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>// <a href="https://godbolt.org/z/Fb7vvs">https://godbolt.org/z/Fb7vvs</a>
// clang++ -Wreturn-std-move -std=c++17 t.cpp
#include <vector>
auto f() -> std::vector<int>;
auto g(std::vector<int> &) -> void;
auto h() -> std::vector<int>
{
auto v = f();
g(v);
return v;
}
auto i() -> std::vector<int>
{
auto &&v = f(); // WARNING: local variable 'v' will be copied despite
being returned by name
g(v);
return v;
}
--------------------------
The above code gives a warning with return-std-move. However, if we replace
`auto &&` by `auto`, as done in h(), we don't get a warning.
In not familiar enough with the standard to know if this warning is indeed
doing the right thing.
If this is correct, it would be really helpful if the warning message contained
a note explaining what is the reason for this not being copied by name. This
way, the root cause could be tackled instead of the symptom.</pre>
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