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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - std::forward_list::swap noexcept specification not using correct member type"
href="https://bugs.llvm.org/show_bug.cgi?id=50224">50224</a>
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</tr>
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<th>Summary</th>
<td>std::forward_list::swap noexcept specification not using correct member type
</td>
</tr>
<tr>
<th>Product</th>
<td>libc++
</td>
</tr>
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<th>Version</th>
<td>12.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>Linux
</td>
</tr>
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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>
</tr>
<tr>
<th>Component</th>
<td>All Bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>p.hyundeok76@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
</td>
</tr></table>
<p>
<div>
<pre>The current implementation of `std::forward_list::swap` is as follows:
```cpp
_LIBCPP_INLINE_VISIBILITY
void swap(__forward_list_base& __x)
#if _LIBCPP_STD_VER >= 14
_NOEXCEPT;
#else
_NOEXCEPT_(!__node_traits::propagate_on_container_move_assignment::value ||
__is_nothrow_swappable<__node_allocator>::value);
```
which uses `propagate_on_container_move_assignment` for `noexcept`
specification.
This must use `propagate_on_container_swap` for checking according to
[[container.requirements.general/8]](<a href="http://eel.is/c++draft/container.requirements.general#8">http://eel.is/c++draft/container.requirements.general#8</a>).
When the change is applied, the declaration should look like:
```cpp
_LIBCPP_INLINE_VISIBILITY
void swap(__forward_list_base& __x)
#if _LIBCPP_STD_VER >= 14
_NOEXCEPT;
#else
_NOEXCEPT_(!__node_traits::propagate_on_container_swap::value ||
__is_nothrow_swappable<__node_allocator>::value);
```
and the definition should be as follows:
```cpp
template <class _Tp, class _Alloc>
inline
void
__forward_list_base<_Tp, _Alloc>::swap(__forward_list_base& __x)
#if _LIBCPP_STD_VER >= 14
_NOEXCEPT
#else
_NOEXCEPT_(!__node_traits::propagate_on_container_swap::value ||
__is_nothrow_swappable<__node_allocator>::value)
#endif
{
_VSTD::__swap_allocator(__alloc(), __x.__alloc(),
integral_constant<bool,
__node_traits::propagate_on_container_swap::value>());
using _VSTD::swap;
swap(__before_begin()->__next_, __x.__before_begin()->__next_);
}
```</pre>
</div>
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