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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - std::~unique_ptr is inefficient"
href="https://bugs.llvm.org/show_bug.cgi?id=45848">45848</a>
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<th>Summary</th>
<td>std::~unique_ptr is inefficient
</td>
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<th>Product</th>
<td>libc++
</td>
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<th>Version</th>
<td>unspecified
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<th>Hardware</th>
<td>Macintosh
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<th>OS</th>
<td>MacOS X
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<th>Status</th>
<td>NEW
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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>All Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>jsbache@adobe.com
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
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<p>
<div>
<pre>The dtor of unique_ptr is implemented in terms of reset (which defaults to a
set of a nullptr).
~unique_ptr() { reset(); }
This is inefficient as the effect is that the dtor modifies the address held by
its ptr
__ptr_.first() = __p;
This causes address invalidation (and a related cacheline invalidation).
Since this is in the dtor, noone should read that value again.
~unique_ptr should be implemented in terms of the contained destructor only:
~unique_ptr() {
const pointer ptr = __ptr_.first();
if (ptr)
__ptr_.second()(ptr);
}</pre>
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