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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - std::map copy assignment fails for mapped types without copy assignment"
href="https://bugs.llvm.org/show_bug.cgi?id=36703">36703</a>
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<th>Summary</th>
<td>std::map copy assignment fails for mapped types without copy assignment
</td>
</tr>
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<th>Product</th>
<td>libc++
</td>
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<th>Version</th>
<td>6.0
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<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>
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<th>Reporter</th>
<td>plroskin@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
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<p>
<div>
<pre>I've noticed that a program I'm working on would compile with libstdc++ but not
with libc++. Here's a minimal version:
#include <map>
struct Mapped
{
Mapped() {};
Mapped(const Mapped&) = default;
Mapped(Mapped&&) = delete;
Mapped& operator=(const Mapped&) = delete;
Mapped& operator=(Mapped&&) = delete;
~Mapped() = default;
};
using MyMap = std::map<int, Mapped>;
int main()
{
const MyMap map1{};
MyMap map2{};
map2 = map1;
// this would work:
// map2 = MyMap{map1};
return 0;
}
clang 6 would complain:
/opt/clang-6.0.0/bin/../include/c++/v1/map:629:15: error: object of type
'std::__1::pair<int, Mapped>' cannot be assigned because its copy assignment
operator is implicitly deleted
{__nc = __v.__cc; return *this;}
I see that a similar <a class="bz_bug_link
bz_status_RESOLVED bz_closed"
title="RESOLVED INVALID - map<const, const> fails copy-assignment"
href="show_bug.cgi?id=23304">bug #23304</a> was closed as invalid. Still, I believe there
is a room for improvement here for libc++ to be a drop-in replacement for
libstdc++. Maybe there should be a fallback copy assignment implementation that
avoids using copy assignment for the mapped type.
I would have hard time explaining to my colleagues why I need to create a
temporary map object to placate libc++.</pre>
</div>
</p>
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