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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Spurious interaction between noexcept specs. for move/copy assignment"
href="https://bugs.llvm.org/show_bug.cgi?id=38983">38983</a>
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<th>Summary</th>
<td>Spurious interaction between noexcept specs. for move/copy assignment
</td>
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<th>Product</th>
<td>clang
</td>
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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>MacOS X
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>oliver.rosten@googlemail.com
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</tr>
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<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>The following (contrived) code appears to indicate a spurious dependency
between the exception specifications for the move/copy assignment operators.
template<class T>
class wrapper
{
T& m_Ref;
// Reported problem disappears if reference_wrapper is used instead
public:
wrapper(T& ref) : m_Ref{ref} {}
wrapper(const wrapper&) = default;
wrapper(wrapper&&) noexcept = default;
wrapper& operator=(const wrapper&) noexcept(false){}
// 'false' required to reveal bug;
//removing false fixes compilation
wrapper& operator=(wrapper&&) noexcept = default;
};
template<class T, class W>
class thing
{
private:
W m_Member{};
public:
thing(T& ref) : m_Member{ref} {}
thing(const thing&) = default;
thing(thing&&) = default;
thing& operator=(const thing&) = default;
thing& operator=(thing&&) noexcept = default;
};
int x{5};
wrapper<int> w{x}; // fine
thing<int, wrapper<int>> foo{x};
Compiler error message:
exception specification of
explicitly defaulted move assignment operator does not match the
calculated one
thing& operator=(thing&&) noexcept = default;
The last line of code fails to compile due to the exception spec of the *move*
assignment operator not matching the calculated one.
Compilation may be fixed by changing the exception spec. of the *copy*
assignment operator.</pre>
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