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<title>Issue 3073: [networking.ts] (async_)read and (async_)write 
don't support DynamicBuffer lvalues</title>
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don't support DynamicBuffer lvalues">
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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="3073"><a href="lwg-active.html#3073">3073</a>. [networking.ts] (<code>async_</code>)<code>read</code> and (<code>async_</code>)<code>write</code> 
don't support <code>DynamicBuffer</code> lvalues</h3>
<p><b>Section:</b> 17 [networking.ts::buffer.stream] <b>Status:</b> <a href="lwg-active.html#New">New</a>
 <b>Submitter:</b> Christopher Kohlhoff <b>Opened:</b> 2018-02-27 <b>Last modified:</b> 2020-09-06</p>
<p><b>Priority: </b>3
</p>
<p><b>View all issues with</b> <a href="lwg-status.html#New">New</a> status.</p>
<p><b>Discussion:</b></p>
<b>Addresses: networking.ts</b>
<p>Suppose that we have a user-defined class <code>dyn_buf</code> that satisfies the DynamicBuffer 
requirements ([buffer.reqmts.dynamicbuffer]), and is additionally copy-constructible. The following snippet compiles, as expected:</p>
<blockquote><pre>
dyn_buf b;
net::read_until(my_socket, b, "\n");
</pre></blockquote>
<p>However, this next snippet will not compile, when it should:</p>
<blockquote><pre>
dyn_buf b;
net::read(my_socket, b);
</pre></blockquote>

<p>This is due to:</p>
<ul>
<li>the <code>DynamicBuffer</code> template parameter being deduced as <code>dyn_buf&amp;</code>, and</li>
<li>the <code>read</code> overload being specified to not participate in overload resolution unless <code>is_dynamic_buffer_v&lt;DynamicBuffer&gt;</code> is <code>true</code>.</li>
</ul>

<p>This can fixed by changing the test to <code>is_dynamic_buffer_v&lt;decay_t&lt;DynamicBuffer&gt;&gt;</code>.</p>

<p><i>[2019-01-20 Reflector prioritization]</i></p>

<p>Set Priority to 3</p>


<p id="res-3073"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/n4711">N4711</a>.
</p>

<ol>

<li>
<p>Edit 17.5 [networking.ts::buffer.read] as indicated:</p>
<blockquote>
<p>-14- <em>Remarks:</em> This function shall not participate in overload resolution unless 
<code>is_dynamic_buffer_v&lt;<ins>decay_t&lt;</ins>DynamicBuffer<ins>&gt;</ins>&gt;</code> is 
<code>true</code>.</p>
</blockquote>
</li>

<li>
<p>Edit 17.6 [networking.ts::buffer.async.read] as indicated:</p>
<blockquote>
<p>-16- <em>Remarks:</em> This function shall not participate in overload resolution unless 
<code>is_dynamic_buffer_v&lt;<ins>decay_t&lt;</ins>DynamicBuffer<ins>&gt;</ins>&gt;</code> is 
<code>true</code>.</p>
</blockquote>
</li>

<li>
<p>Edit 17.7 [networking.ts::buffer.write] as indicated:</p>
<blockquote>
<p>-14- <em>Remarks:</em> This function shall not participate in overload resolution unless 
<code>is_dynamic_buffer_v&lt;<ins>decay_t&lt;</ins>DynamicBuffer<ins>&gt;</ins>&gt;</code> is 
<code>true</code>.</p>
</blockquote>
</li>

<li>
<p>Edit 17.8 [networking.ts::buffer.async.write] as indicated:</p>
<blockquote>
<p>-16- <em>Remarks:</em> This function shall not participate in overload resolution unless 
<code>is_dynamic_buffer_v&lt;<ins>decay_t&lt;</ins>DynamicBuffer<ins>&gt;</ins>&gt;</code> is 
<code>true</code>.</p>
</blockquote>
</li>
</ol>





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