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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Implement DR 1137 - Real return types for std::conj(float) and friends"
href="https://llvm.org/bugs/show_bug.cgi?id=27741">27741</a>
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<th>Summary</th>
<td>Implement DR 1137 - Real return types for std::conj(float) and friends
</td>
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<th>Product</th>
<td>libc++
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>All Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>hfinkel@anl.gov
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>libc++, unlike libstdc++, does not implement DR 1137, which says that the
return type of std::conj(float) should be float, not std::complex<float>.
inline _LIBCPP_INLINE_VISIBILITY
complex<float>
conj(float __re)
{
return complex<float>(__re);
}
The proposed resolution to DR 1137 was to add:
All of the specified overloads shall have a return type which is the nested
value_type of the effectively cast arguments.
<a href="http://lwg.github.io/issues/lwg-defects.html#1137">http://lwg.github.io/issues/lwg-defects.html#1137</a>
to 26.4.9, although I don't see that text in the standard itself - I'm not sure
what happened in that regard. libstdc++ has:
// DR 1137.
template<typename _Tp>
inline typename __gnu_cxx::__promote<_Tp>::__type
proj(_Tp __x)
{ return __x; }
template<typename _Tp>
inline typename __gnu_cxx::__promote<_Tp>::__type
conj(_Tp __x)
{ return __x; }
We have code that, as a result of this, compiles with libstdc++, but not with
libc++.</pre>
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