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<title>Issue 3086: Possible problem in &sect;[new.delete.single]</title>
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<p><em>This page is a snapshot from the LWG issues list, see the <a href="lwg-active.html">Library Active Issues List</a> for more information and the meaning of <a href="lwg-active.html#New">New</a> status.</em></p>
<h3 id="3086"><a href="lwg-active.html#3086">3086</a>. Possible problem in &sect;[new.delete.single]</h3>
<p><b>Section:</b> 17.6.3.2 <a href="https://wg21.link/new.delete.single">[new.delete.single]</a> <b>Status:</b> <a href="lwg-active.html#New">New</a>
 <b>Submitter:</b> William M. Miller <b>Opened:</b> 2018-03-16 <b>Last modified:</b> 2020-09-06</p>
<p><b>Priority: </b>3
</p>
<p><b>View other</b> <a href="lwg-index-open.html#new.delete.single">active issues</a> in [new.delete.single].</p>
<p><b>View all other</b> <a href="lwg-index.html#new.delete.single">issues</a> in [new.delete.single].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#New">New</a> status.</p>
<p><b>Discussion:</b></p>
<p>
In general requirements on a whole program, as opposed to a single translation unit, generally specify 
"no diagnostic required", since we don't want to require implementations to do multi-translation-unit 
analysis. However, 17.6.3.2 <a href="https://wg21.link/new.delete.single">[new.delete.single]</a> paragraph 11 says,
</p>
<blockquote><p>
If a function with a <code>size</code> parameter is defined, the program shall also define the corresponding 
version without the <code>size</code> parameter.
</p></blockquote>
<p>
This is clearly not restricted to a single translation unit; should "no diagnostic required" be added?
</p>

<p><i>[2018-04-03; Thomas K&ouml;ppe and Tim Song suggest wording]</i></p>


<p><i>[2018-06-18 after reflector discussion]</i></p>

<p>Priority set to 3</p>


<p id="res-3086"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/n4727">N4727</a>.
</p>

<ol>
<li><p>Edit 17.6.3.2 <a href="https://wg21.link/new.delete.single">[new.delete.single]</a> as indicated:</p>
<blockquote>
<pre>
void operator delete(void* ptr) noexcept;
void operator delete(void* ptr, std::size_t size) noexcept;
void operator delete(void* ptr, std::align_val_t alignment) noexcept;
void operator delete(void* ptr, std::size_t size, std::align_val_t alignment) noexcept;
</pre>
<blockquote>
<p>
-10- <i>Effects:</i> [&hellip;]
<p/>
-11- <i>Replaceable:</i> A C++ program may define functions with any of these function signatures, and thereby
displace the default versions defined by the C++ standard library. If a function without a <code>size</code> parameter
is defined, the program should also define the corresponding function with a <code>size</code> parameter. If a
function with a <code>size</code> parameter is defined, the program shall also define the corresponding version
without the <code>size</code> parameter<ins>; no diagnostic is required</ins>. [<i>Note:</i> The default behavior 
below may change in the future, which will require replacing both deallocation functions when replacing the 
allocation function. &mdash; <i>end note</i>]
</p>
</blockquote>
</blockquote>
</li>

<li><p>Edit 17.6.3.3 <a href="https://wg21.link/new.delete.array">[new.delete.array]</a> as indicated:</p>
<blockquote>
<pre>
void operator delete[](void* ptr) noexcept;
void operator delete[](void* ptr, std::size_t size) noexcept;
void operator delete[](void* ptr, std::align_val_t alignment) noexcept;
void operator delete[](void* ptr, std::size_t size, std::align_val_t alignment) noexcept;
</pre>
<blockquote>
<p>
-9- <i>Effects:</i> [&hellip;]
<p/>
-10- <i>Replaceable:</i> A C++ program may define functions with any of these function signatures, and thereby
displace the default versions defined by the C++ standard library. If a function without a <code>size</code> parameter
is defined, the program should also define the corresponding function with a <code>size</code> parameter. If a
function with a <code>size</code> parameter is defined, the program shall also define the corresponding version
without the <code>size</code> parameter<ins>; no diagnostic is required</ins>. [<i>Note:</i> The default behavior 
below may change in the future, which will require replacing both deallocation functions when replacing the 
allocation function. &mdash; <i>end note</i>]
</p>
</blockquote>
</blockquote>
</li>
</ol>





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