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<title>Issue 3778: vector&lt;bool&gt; missing exception specifications</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#C++23">C++23</a> status.</em></p>
<h3 id="3778"><a href="lwg-defects.html#3778">3778</a>. <code>vector&lt;bool&gt;</code> missing exception specifications</h3>
<p><b>Section:</b> 23.3.14.1 <a href="https://wg21.link/vector.bool.pspc">[vector.bool.pspc]</a> <b>Status:</b> <a href="lwg-active.html#C++23">C++23</a>
 <b>Submitter:</b> Alisdair Meredith <b>Opened:</b> 2022-09-13 <b>Last modified:</b> 2023-11-22</p>
<p><b>Priority: </b>Not Prioritized
</p>
<p><b>View all other</b> <a href="lwg-index.html#vector.bool.pspc">issues</a> in [vector.bool.pspc].</p>
<p><b>View all issues with</b> <a href="lwg-status.html#C++23">C++23</a> status.</p>
<p><b>Discussion:</b></p>
<p>
As noted back in <a href="https://wg21.link/P0177R2" title=" Cleaning up allocator_traits">P0177R2</a>, the primary template for <code>vector</code> has picked 
up some exception specification, but the partial specialization for <code>vector&lt;bool&gt;</code> 
has not been so updated.
<p/>
Several other changes have been made to <code>vector</code> in the intervening years, but these 
particular exception specifications have still not been updated. Note that the free-function 
<code>swap</code> in the header synopsis will automatically pick up this update once applied.
</p>

<p><i>[2022-09-28; Reflector poll]</i></p>

<p>
Set status to Tentatively Ready after seven votes in favour during reflector poll.
</p>

<p><i>[2022-11-12 Approved at November 2022 meeting in Kona. Status changed: Voting &rarr; WP.]</i></p>



<p id="res-3778"><b>Proposed resolution:</b></p>
<p>
This wording is relative to <a href="https://wg21.link/N4917" title=" Working Draft, Standard for Programming Language C++">N4917</a>.
</p>

<ol>

<li><p>Modify 23.3.14.1 <a href="https://wg21.link/vector.bool.pspc">[vector.bool.pspc]</a>, partial class template 
<code>vector&lt;bool, Allocator&gt;</code> synopsis, as indicated:</p>

<blockquote>
<pre>
namespace std {
  template&lt;class Allocator&gt;
  class vector&lt;bool, Allocator&gt; {
  public:
    [&hellip;]
    // <i>construct/copy/destroy</i>
    constexpr vector() <ins>noexcept(noexcept(Allocator()))</ins> : vector(Allocator()) { }
    constexpr explicit vector(const Allocator&amp;) <ins>noexcept</ins>;
    constexpr explicit vector(size_type n, const Allocator&amp; = Allocator());
    constexpr vector(size_type n, const bool&amp; value, const Allocator&amp; = Allocator());
    template&lt;class InputIterator&gt;
      constexpr vector(InputIterator first, InputIterator last, const Allocator&amp; = Allocator());
    template&lt;container-compatible-range &lt;bool&gt; R&gt;
      constexpr vector(from_range_t, R&amp;&amp; rg, const Allocator&amp; = Allocator());
    constexpr vector(const vector&amp; x);
    constexpr vector(vector&amp;&amp; x) <ins>noexcept</ins>;
    constexpr vector(const vector&amp;, const type_identity_t&lt;Allocator&gt;&amp;);
    constexpr vector(vector&amp;&amp;, const type_identity_t&lt;Allocator&gt;&amp;);
    constexpr vector(initializer_list&lt;bool&gt;, const Allocator&amp; = Allocator());
    constexpr ~vector();
    constexpr vector&amp; operator=(const vector&amp; x);
    constexpr vector&amp; operator=(vector&amp;&amp; x)
      <ins>noexcept(allocator_traits&lt;Allocator&gt;::propagate_on_container_move_assignment::value ||</ins>
               <ins>allocator_traits&lt;Allocator&gt;::is_always_equal::value)</ins>;
    constexpr vector&amp; operator=(initializer_list&lt;bool&gt;);
    template&lt;class InputIterator&gt;
      constexpr void assign(InputIterator first, InputIterator last);
    template&lt;container-compatible-range &lt;bool&gt; R&gt;
      constexpr void assign_range(R&amp;&amp; rg);
    constexpr void assign(size_type n, const bool&amp; t);
    constexpr void assign(initializer_list&lt;bool&gt;);
    constexpr allocator_type get_allocator() const noexcept;
  
    [&hellip;]
    constexpr iterator erase(const_iterator position);
    constexpr iterator erase(const_iterator first, const_iterator last);
    constexpr void swap(vector&amp;)
      <ins>noexcept(allocator_traits&lt;Allocator&gt;::propagate_on_container_swap::value ||</ins>
               <ins>allocator_traits&lt;Allocator&gt;::is_always_equal::value)</ins>;
    constexpr static void swap(reference x, reference y) noexcept;
    constexpr void flip() noexcept; // <i>flips all bits</i>
    constexpr void clear() noexcept;
  };
}
</pre>
</blockquote>
</li>

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