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<title>Issue 4163: Can the overload of std::num_get::do_get for bool call the overload for long?</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#NAD">Tentatively NAD</a> status.</em></p>
<h3 id="4163"><a href="lwg-active.html#4163">4163</a>. Can the overload of <code>std::num_get::do_get</code> for <code>bool</code> call the overload for <code>long</code>?</h3>
<p><b>Section:</b> 28.3.4.3.2.3 <a href="https://wg21.link/facet.num.get.virtuals">[facet.num.get.virtuals]</a> <b>Status:</b> <a href="lwg-active.html#NAD">Tentatively NAD</a>
 <b>Submitter:</b> Jiang An <b>Opened:</b> 2024-09-29 <b>Last modified:</b> 2025-02-07</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View other</b> <a href="lwg-index-open.html#facet.num.get.virtuals">active issues</a> in [facet.num.get.virtuals].</p>
<p><b>View all other</b> <a href="lwg-index.html#facet.num.get.virtuals">issues</a> in [facet.num.get.virtuals].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#Tentatively NAD">Tentatively NAD</a> status.</p>
<p><b>Discussion:</b></p>
<p>
28.3.4.3.2.3 <a href="https://wg21.link/facet.num.get.virtuals">[facet.num.get.virtuals]</a>/6 currently says:
</p>
<blockquote style="border-left: 3px solid #ccc;padding-left: 15px;">
<p>
<i>Effects</i>: If <code>(str.flags()&amp;ios_base::boolalpha) == 0</code> then input proceeds as it would for a 
<code>long</code> except that if a value is being stored into <code>val</code>, [&hellip;]
</p>
</blockquote>
<p>
It is unclear whether an implementation is allowed to call the overload for <code>long</code> in this case. 
Currently, libc++'s version calls that overload, while libstdc++ and MSVC STL's don't 
(<a href="https://godbolt.org/z/83M1hKThv">example</a>).
<p/>
As the divergence implementation strategies is observable, perhaps we should clarify on this.
</p>

<p><i>[2025-02-07; Reflector poll: NAD]</i></p>

<p>
I think this is just a libc++ bug.
The wording says it "proceeds as it would for <code class='backtick'>long</code>", which is not the same as
actually making a virtual call to <code class='backtick'>do_get</code> for <code class='backtick'>long</code>. It can either duplicate
the code from <code class='backtick'>do_get</code> for <code class='backtick'>long</code>, or make a non-virtual (i.e. qualified) call
to <code class='backtick'>num_get::do_get</code>.
</p>



<p id="res-4163"><b>Proposed resolution:</b></p>





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