<section xmlns="http://docbook.org/ns/docbook" version="5.0" 
	 xml:id="status.iso.2017" xreflabel="Status C++ 2017">
<?dbhtml filename="status_iso_cxx2017.html"?>

<info><title>C++ 2017</title>
  <keywordset>
    <keyword>ISO C++</keyword>
    <keyword>2017</keyword>
  </keywordset>
</info>

<para>
In this implementation the <literal>-std=gnu++17</literal> or
<literal>-std=c++17</literal> flag must be used to enable language
and library
features. See <link linkend="manual.intro.using.flags">dialect</link>
options. The pre-defined symbol
<constant>__cplusplus</constant> is used to check for the
presence of the required flag.
</para>

<para>
This section describes the C++17 and library TS support in mainline GCC SVN,
not in any particular release.
</para>

<para>
The following table lists new library features that are included in
the C++17 standard. The "Proposal" column provides a link to the
ISO C++ committee proposal that describes the feature, while the "Status"
column indicates the first version of GCC that contains an implementation of
this feature (if it has been implemented).
The "SD-6 Feature Test" column shows the corresponding macro or header from
<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://isocpp.org/std/standing-documents/sd-6-sg10-feature-test-recommendations">SD-6:
Feature-testing recommendations for C++</link>.
</para>

<table frame="all" xml:id="table.cxx17_status">
<title>C++ 2017 Implementation Status</title>

<tgroup cols="4" align="left" colsep="0" rowsep="1">
<colspec colname="c1"/>
<colspec colname="c2"/>
<colspec colname="c3"/>
<colspec colname="c4"/>
  <thead>
    <row>
      <entry>Library Feature</entry>
      <entry>Proposal</entry>
      <entry>Status</entry>
      <entry>SD-6 Feature Test</entry>
    </row>
  </thead>

  <tbody>

    <row>
      <?dbhtml bgcolor="#C8B0B0" ?>
      <entry>
	<code>constexpr std::hardware_{constructive,destructive}_interference_size</code>
      </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0154r1.html">
	P0154R1
	</link>
      </entry>
      <entry align="center"> No </entry>
      <entry> <code>__cpp_lib_hardware_interference_size >= 201603</code> </entry>
    </row>

    <row>
      <entry> Core Issue 1776: Replacement of class objects containing reference members</entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0137r1.html">
	P0137R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry> <code>__cpp_lib_launder >= 201606</code> </entry>
    </row>

    <row>
      <entry>Wording for <code>std::uncaught_exceptions</code></entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/JTC1/sc22/WG21/docs/papers/2014/n4259.pdf">
	  N4259
	</link>
      </entry>
      <entry align="center">6.1</entry>
      <entry><code>__cpp_lib_uncaught_exceptions >= 201411</code></entry>
    </row>

    <row>
      <entry> C++17 should refer to C11 instead of C99 </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0063r3.html">
	P0063R3
	</link>
      </entry>
      <entry align="center"> 9.1 </entry>
      <entry/>
    </row>

    <row>
      <entry> Variant: a type-safe union for C++17 </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0088r3.html">
	P0088R3
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry> <code>__has_include(&lt;variant&gt;)</code>,
              <code>__cpp_lib_variant >= 201603</code>
              (since 7.3, see Note 1)
      </entry>
    </row>

    <row>
      <entry> Library Fundamentals V1 TS Components: <code>optional</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0220r1.html">
	P0220R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry> <code>__has_include(&lt;optional&gt;)</code>,
              <code>__cpp_lib_optional >= 201603</code>
              (since 7.3, see Note 1)
      </entry>
    </row>

    <row>
      <entry> Library Fundamentals V1 TS Components: <code>any</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0220r1.html">
	P0220R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry> <code>__has_include(&lt;any&gt;)</code>,
              <code>__cpp_lib_any >= 201603</code>
              (since 7.3, see Note 1)
      </entry>
    </row>

    <row>
      <entry> Library Fundamentals V1 TS Components: <code>string_view</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0220r1.html">
	P0220R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry> <code>__has_include(&lt;string_view&gt;)</code>,
              <code>__cpp_lib_string_view >= 201603</code>
              (since 7.3, see Note 1)
      </entry>
    </row>

    <row>
      <entry> Library Fundamentals V1 TS Components: <code>memory_resource</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0220r1.html">
	P0220R1
	</link>
      </entry>
      <entry align="center"> 9.1 </entry>
      <entry> <code>__has_include(&lt;memory_resource&gt;)</code>,
              <code>__cpp_lib_memory_resource >= 201603</code>
      </entry>
    </row>

    <row>
      <entry> Library Fundamentals V1 TS Components: <code>apply</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0220r1.html">
	P0220R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry> <code>__cpp_lib_apply >= 201603</code> </entry>
    </row>

    <row>
      <entry> Library Fundamentals V1 TS Components: <code>shared_ptr&lt;T[]&gt;</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0220r1.html">
	P0220R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry> <code>__cpp_lib_shared_ptr_arrays >= 201603</code> </entry>
    </row>

    <row>
      <entry> Library Fundamentals V1 TS Components: Searchers </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0220r1.html">
	P0220R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry> <code>__cpp_lib_boyer_moore_searcher >= 201603</code> </entry>
    </row>

    <row>
      <entry> Library Fundamentals V1 TS Components: Sampling </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0220r1.html">
	P0220R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry> <code>__cpp_lib_sample >= 201603</code> </entry>
    </row>

    <row>
      <entry> Constant View: A proposal for a <code>std::as_const</code> helper function template	</entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="">
	P0007R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_as_const >= 201510 </code></entry>
    </row>

    <row>
      <entry> Improving pair and tuple </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4387">
	N4387
	</link>
      </entry>
      <entry align="center"> 6.1 </entry>
      <entry> N/A </entry>
    </row>

    <row>
      <entry> <code>make_from_tuple</code>: apply for construction </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0209r2.pdf">
	P0209R2
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_make_from_tuple >= 201606 </code></entry>
    </row>

    <row>
      <?dbhtml bgcolor="#C8B0B0" ?>
      <entry>
        Removing <code>auto_ptr</code>, <code>random_shuffle()</code>,
        And Old <code>&lt;functional&gt;</code> Stuff
      </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4190.htm">
	  N4190
	</link>
      </entry>
      <entry align="center">No (kept for backwards compatibility)</entry>
      <entry/>
    </row>

    <row>
      <?dbhtml bgcolor="#C8B0B0" ?>
      <entry> Deprecating Vestigial Library Parts in C++17 </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0174r2.html">
	P0174R2
	</link>
      </entry>
      <entry align="center"> No  (kept for backwards compatibility)</entry>
      <entry/>
    </row>

    <row>
      <entry> Making <code>std::owner_less</code> more flexible </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0074r0.html">
	P0074R0
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_transparent_operators >= 201510 </code></entry>
    </row>

    <row>
      <entry> <code>std::addressof</code> should be constexpr </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0304r0.html#2296">
	LWG2296
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_addressof_constexpr >= 201603 </code></entry>
    </row>

    <row>
      <entry> Safe conversions in <code>unique_ptr&lt;T[]&gt;</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4089.pdf">
	N4089
	</link>
      </entry>
      <entry align="center"> 6 </entry>
      <entry/>
    </row>

    <row>
      <entry> LWG 2228: Missing SFINAE rule in unique_ptr templated assignment </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4366.html">
	  N4366
	</link>
      </entry>
      <entry align="center"> 6 </entry>
      <entry/>
    </row>

    <row>
      <entry> Re-enabling <code>shared_from_this</code></entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0033r1.html">
	P0033R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code>__cpp_lib_enable_shared_from_this >= 201603</code></entry>
    </row>

    <row>
      <entry> A proposal to add <code>invoke</code> function template </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4169.html">
	N4169
	</link>
      </entry>
      <entry align="center"> 6.1 </entry>
      <entry><code> __cpp_lib_invoke >= 201411 </code></entry>
    </row>

    <row>
      <entry>TriviallyCopyable <code>reference_wrapper</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4277.html">
	  N4277
	</link>
      </entry>
      <entry align="center"> 5.1 </entry>
      <entry/>
    </row>

    <row>
      <entry> Adopt <code>not_fn</code> from Library Fundamentals 2 for C++17 </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0005r4.html">
	P0005R4
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code>__cpp_lib_not_fn >= 201603</code></entry>
    </row>

    <row>
      <entry> Fixes for <code>not_fn</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0358r1.html">
	P0358R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry/>
    </row>

    <row>
      <entry> Fixing a design mistake in the searchers interface in Library Fundamentals </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0253r1.pdf">
	P0253R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry/>
    </row>

    <row>
      <entry> Extending memory management tools </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0040r3.html">
	P0040R3
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code>__cpp_lib_raw_memory_algorithms &gt;= 201606L</code></entry>
    </row>

    <row>
      <entry> <code>shared_ptr::weak_type</code></entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0163r0.html">
	P0163R0
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_shared_ptr_weak_type >= 201606</code></entry>
    </row>

    <row>
      <entry>Transformation Trait Alias <code>void_t</code></entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/JTC1/sc22/WG21/docs/papers/2014/n3911.pdf">
	  N3911
	</link>
      </entry>
      <entry align="center">6.1</entry>
      <entry><code> __cpp_lib_void_t >= 201411</code></entry>
    </row>

    <row>
      <entry> Wording for <code>bool_constant</code>, revision 1 </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4389.html">
	  N4389
	</link>
      </entry>
      <entry align="center">6.1</entry>
      <entry><code> __cpp_lib_bool_constant >= 201505</code></entry>
    </row>

    <row>
      <entry> Adopt Type Traits Variable Templates from Library Fundamentals TS for C++17</entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0006r0.html">
	P0006R0
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_type_trait_variable_templates >= 201510 </code></entry>
    </row>

    <row>
      <entry> Logical Operator Type Traits</entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0013r1.html">
	P0013R1
	</link>
      </entry>
      <entry align="center"> 6.1 </entry>
      <entry><code> __cpp_lib_logical_traits >= 201510 </code></entry>
    </row>

    <row>
      <entry> Adding [nothrow-]swappable traits </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0185r1.html">
	P0185R1
	</link>
      </entry>
      <entry align="center"> 7 (<code>__is_swappable</code> available since 6.1)</entry>
      <entry><code> __cpp_lib_is_swappable >= 201603 </code></entry>
    </row>

    <row>
      <entry> <code>is_callable</code>, the missing INVOKE related trait</entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0077r2.html">
	P0077R2
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_is_callable >= 201603 </code></entry>
    </row>

    <row>
      <entry> has_unique_object_representations </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0258r2.html">
	P0258R2
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_has_unique_object_representations >= 201606 </code></entry>
    </row>

    <row>
      <entry> Polishing <code>&lt;chrono&gt;</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0092r1.html">
	P0092R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_chrono >= 201510 </code></entry>
    </row>

    <row>
      <entry> Adding more constexpr to <code>&lt;chrono&gt;</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0505r0.html">
	P0505R0
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_chrono >= 201611 </code>
             (since 7.3, see Note 2)
      </entry>
    </row>

    <row>
      <entry> Constexpr for <code>std::char_traits</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0426r1.html">
	P0426R1
	</link>
      </entry>
      <entry align="center"> 8.1 </entry>
      <entry><code> __cpp_lib_constexpr_char_traits >= 201611 </code></entry>
    </row>

    <row>
      <entry> Integrating <code>std::string_view</code> and <code>std::string</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0254r2.pdf">
	P0254R2
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> </code></entry>
    </row>

    <row>
      <entry> Give 'std::string' a non-const '.data()' member function </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0272r1.html">
	P0272R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> </code></entry>
    </row>

    <row>
      <entry>Cleaning-up noexcept in the Library</entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4258.pdf">
	  N4258
	</link>
      </entry>
      <entry align="center">6.1</entry>
      <entry><code> __cpp_lib_allocator_traits_is_always_equal >= 201411 </code></entry>
    </row>

    <row>
      <entry>Contiguous Iterators </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4284.html">
	  N4284
	</link>
      </entry>
      <entry align="center">N/A</entry>
      <entry/>
    </row>

    <row>
      <entry> Minimal incomplete type support for standard containers </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4510.html">
	N4510
	</link>
      </entry>
      <entry align="center"> 3.0 </entry>
      <entry><code> __cpp_lib_incomplete_container_elements >= 201505 </code>
	     (since 6.2, see Note 2)
      </entry>
    </row>

    <row>
      <entry> Emplace return type </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0084r2.pdf">
	P0084R2
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry/>
    </row>

    <row>
      <entry>Improved insertion interface for unique-key maps</entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4279.html">
	  N4279
	</link>
      </entry>
      <entry align="center"> 6.1 </entry>
      <entry><code> __cpp_lib_map_try_emplace >= 201411</code>,
	     <code> __cpp_lib_unordered_map_try_emplace >= 201411</code>
      </entry>
    </row>

    <row>
      <entry> Splicing Maps and Sets </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0083r3.pdf">
	P0083R3
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_node_extract >= 201606 </code></entry>
    </row>

    <row>
      <entry>Non-member <code>size()</code> and more</entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4280.pdf">
	  N4280
	</link>
      </entry>
      <entry align="center"> 6.1 </entry>
      <entry><code> __cpp_lib_nonmember_container_access >= 201411 </code></entry>
    </row>

    <row>
      <entry> A Proposal to Add Constexpr Modifiers to <code>reverse_iterator</code>, <code>move_iterator</code>, <code>array</code> and Range Access </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0031r0.html">
	P0031R0
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_array_constexpr >= 201603 </code></entry>
    </row>

    <row>
      <?dbhtml bgcolor="#B0B0B0" ?>
      <entry> The Parallelism TS Should be Standardized	 </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0024r2.html">
	P0024R2
	</link>
      </entry>
      <entry align="center"> 9.1 </entry>
      <entry><code> __has_include(&lt;execution&gt;) </code>,
	     <code> __cpp_lib_execution >= 201603 </code>,
	     <code> __cpp_lib_parallel_algorithm >= 201603 </code>
             (requires linking with <code>-ltbb</code>, see Note 3)
      </entry>
    </row>

    <row>
      <entry> An algorithm to "clamp" a value between a pair of boundary values </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0025r0.html">
	P0025R0
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_clamp >= 201603 </code></entry>
    </row>

    <row>
      <entry> Adopt Selected Library Fundamentals V2 Components for C++17 </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0295r0.pdf">
	P0295R0
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_gcd_lcm >= 201606 </code></entry>
    </row>

    <row>
      <entry> Proposal to Introduce a 3-Argument Overload to <code>std::hypot</code> </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/p0030r1.pdf">
	P0030R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_hypot >= 201603 </code></entry>
    </row>

    <row>
      <entry> Mathematical Special Functions for C++17 </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0226r1.pdf">
	P0226R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_math_special_functions >= 201603 </code>
	     (see Note 4)
      </entry>
    </row>

    <row>
      <entry>Adopt the File System TS for C++17	 </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0218r1.html">
	P0218R1
	</link>
      </entry>
      <entry align="center"> 8.1 </entry>
      <entry><code> __has_include(&lt;filesystem&gt;) </code>,
	     <code> __cpp_lib_filesystem >= 201603 </code>
	     (GCC 8.x requires linking with <code>-lstdc++fs</code>)
      </entry>
    </row>

    <row>
      <entry> Relative Paths for Filesystem</entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0219r1.html">
	P0219R1
	</link>
      </entry>
      <entry align="center"> 8.1 </entry>
      <entry><code> __cpp_lib_filesystem >= 201606 </code></entry>
    </row>

    <row>
      <entry> Adapting string_view by filesystem paths </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0392r0.pdf">
	P0392R0
	</link>
      </entry>
      <entry align="center"> 8.1 </entry>
      <entry><code> __cpp_lib_filesystem >= 201606 </code></entry>
    </row>

    <row>
      <entry> Directory Entry Caching for Filesystem </entry>
      <entry>
       <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0317r1.html">
       P0317R1
       </link>
      </entry>
      <entry align="center"> 8.1 </entry>
      <entry><code> __cpp_lib_filesystem >= 201703 </code></entry>
     </row>

    <row>
      <entry> constexpr <code>atomic&lt;T&gt;::is_always_lock_free</code>	 </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0152r1.html">
	P0152R1
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_atomic_is_always_lock_free >= 201603 </code></entry>
    </row>

    <row>
      <entry>A proposal to add <code>shared_mutex</code> (untimed) (Revision 4)</entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4508.html">
	  N4508
	</link>
      </entry>
      <entry align="center"> 6.1 </entry>
      <entry><code> __cpp_lib_shared_mutex >= 201505 </code></entry>
    </row>

    <row>
      <entry> Variadic <code>lock_guard</code> (Rev. 5) </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0156r2.html">
	P0156R2
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_scoped_lock >= 201703 </code></entry>
    </row>

    <row>
      <entry> A byte type definition </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0298r3.pdf">
	P0298R3
	</link>
      </entry>
      <entry align="center"> 7.1 </entry>
      <entry><code> __cpp_lib_byte >= 201603 </code> (since 7.3, see Note 2)
      </entry>
    </row>

    <row>
      <?dbhtml bgcolor="#B0B0B0" ?>
      <entry> Elementary string conversions </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0067r5.html">
	P0067R5
	</link>
      </entry>
      <entry align="center"> 8.1 (only integral types supported) </entry>
      <entry><code> __has_include(&lt;charconv&gt;) </code>
             <code> __cpp_lib_to_chars >= 201611 </code></entry>
    </row>

    <row>
      <entry> Homogeneous interface for variant, any and optional </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0032r3.pdf">
	P0032R3
	</link>
      </entry>
      <entry align="center"> 7.1  </entry>
      <entry>
             <code> __cpp_lib_any >= 201606 </code>,
             <code> __cpp_lib_optional >= 201606 </code>,
             <code> __cpp_lib_variant >= 201606 </code>
      </entry>
    </row>

    <row>
      <entry> Making Optional Greater Equal Again </entry>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2016/p0307r2.pdf">
	P0307R2
	</link>
      </entry>
      <entry align="center"> 7.1  </entry>
      <entry> <code> __cpp_lib_optional >= 201606 </code> </entry>
    </row>

  </tbody>
</tgroup>
</table>

<para>
Note 1: This feature is supported in GCC 7.1 and 7.2 but before GCC 7.3 the
<code>__cpp_lib</code> macro is not defined, and compilation will fail if the
header is included without using <option>-std</option> to enable C++17 support.
</para>

<para>
Note 2: This feature is supported in older releases but the
<code>__cpp_lib</code> macro is not defined to the right value
(or not defined at all) until the version shown in parentheses.
</para>

<para>
Note 3: The Parallel Algorithms have an external dependency on Intel TBB 2018
or later. If the <filename class="headerfile">&lt;execution&gt;</filename>
header is included then <code>-ltbb</code> must be used to link to TBB.
</para>

<para>
Note 4: The mathematical special functions are enabled in C++17 mode from
GCC 7.1 onwards. For GCC 6.x or for C++11/C++14 define
<code>__STDCPP_WANT_MATH_SPEC_FUNCS__</code> to a non-zero value
and test for <code>__STDCPP_MATH_SPEC_FUNCS__ >= 201003L</code>.
</para>

<table frame="all" xml:id="table.cxx17_ts_status">
<title>C++ Technical Specifications Implementation Status</title>

<tgroup cols="4" align="left" colsep="0" rowsep="1">
<colspec colname="c1"/>
<colspec colname="c2"/>
<colspec colname="c3"/>
<colspec colname="c4"/>
  <thead>
    <row>
      <entry>Paper</entry>
      <entry>Title</entry>
      <entry>Status</entry>
      <entry>Comments</entry>
    </row>
  </thead>

  <tbody>

    <row>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2014/n4076.html">
	  N4076
	</link>
      </entry>
      <entry>A generalized callable negator</entry>
      <entry>Y</entry>
      <entry>Library Fundamentals 2 TS</entry>
    </row>

    <row>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2014/n4273.htm">
	  N4273
	</link>
      </entry>
      <entry>Uniform Container Erasure</entry>
      <entry>Y</entry>
      <entry>Library Fundamentals 2 TS</entry>
    </row>

    <row>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4061.pdf">
	  N4061
	</link>
      </entry>
      <entry>Greatest Common Divisor and Least Common Multiple</entry>
      <entry>Y</entry>
      <entry>Library Fundamentals 2 TS</entry>
    </row>

    <row>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4066.htm">
	  N4066
	</link>
      </entry>
      <entry>Delimited iterators</entry>
      <entry>Y</entry>
      <entry>Library Fundamentals 2 TS</entry>
    </row>

    <row>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4282.pdf">
	  N4282
	</link>
      </entry>
      <entry>The World's Dumbest Smart Pointer</entry>
      <entry>Y</entry>
      <entry>Library Fundamentals 2 TS</entry>
    </row>


    <row>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4388.html">
	  N4388
	</link>
      </entry>
      <entry>Const-Propagating Wrapper</entry>
      <entry>Y</entry>
      <entry>Library Fundamentals 2 TS</entry>
    </row>

    <row>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4391.html">
	  N4391
	</link>
      </entry>
      <entry> <code>make_array</code>, revision 4 </entry>
      <entry>Y</entry>
      <entry>Library Fundamentals 2 TS</entry>
    </row>

    <row>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4502.pdf">
	  N4502
	</link>
      </entry>
      <entry> Support for the C++ Detection Idiom, V2 </entry>
      <entry>Y</entry>
      <entry>Library Fundamentals 2 TS</entry>
    </row>

    <row>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4519.pdf">
	  N4519
	</link>
      </entry>
      <entry> Source-Code Information Capture </entry>
      <entry>Y</entry>
      <entry>Library Fundamentals 2 TS</entry>
    </row>

    <row>
      <?dbhtml bgcolor="#C8B0B0" ?>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4521.html">
	  N4521
	</link>
      </entry>
      <entry> Merge Fundamentals V1 into V2 </entry>
      <entry>
        N (components from V1 are still in namespace
        <code>fundamentals_v1</code>)
      </entry>
      <entry>Library Fundamentals 2 TS</entry>
    </row>

    <row>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://open-std.org/JTC1/SC22/WG21/docs/papers/2015/p0013r1.html">
	  P0013R1
	</link>
      </entry>
      <entry>Logical Operator Type Traits (revision 1)</entry>
      <entry>Y</entry>
      <entry>Library Fundamentals 2 TS</entry>
    </row>

    <row>
      <entry>
	<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4531.html">
	  N4531
	</link>
      </entry>
      <entry>std::rand replacement, revision 3</entry>
      <entry>Y</entry>
      <entry>Library Fundamentals 2 TS</entry>
    </row>

  </tbody>
</tgroup>
</table>

<section xml:id="iso.2017.specific" xreflabel="Implementation Specific"><info><title>Implementation Specific Behavior</title></info>

   <para>For behaviour which is also specified by previous standards,
      see <link linkend="iso.1998.specific">C++ 1998/2003 Implementation
      Specific Behavior</link> and <link linkend="iso.2011.specific">C++
      2011 Implementation Specific Behavior</link>. This section only
      documents behaviour which is new in the 2017 standard.
   </para>

   <para>
      <emphasis>20.5.1.2 [headers]</emphasis>
      Whether names from Annex K are declared by C++ headers depends on
      whether the underlying C library supports Annex K and declares the
      names. For the GNU C library, there is no Annex K support and so
      none of its names are declared by C++ headers.
   </para>

   <para>
      <emphasis>23.6.5 [optional.bad_optional_access]</emphasis>
      <code>what()</code> returns <literal>"bad optional access"</literal>.
   </para>

   <para>
      <emphasis>23.7.3 [variant.variant]</emphasis>
      <classname>variant</classname> supports over-aligned types.
   </para>

   <para>
      <emphasis>23.7.10 [variant.bad.access]</emphasis>
      <code>what()</code> returns <literal>"Unexpected index"</literal>.
   </para>

   <para>
      <emphasis>23.12.5.2 [memory.resource.pool.options]</emphasis>
      Let S equal <code>numeric_limits&lt;size_t&gt;::digits</code>.
      The limit for maximum number of blocks in a chunk is given by
      <inlineequation><mathphrase>2<superscript>N</superscript>-1</mathphrase></inlineequation>,
      where N is <inlineequation><mathphrase>min(19, 3 + S/2)</mathphrase></inlineequation>.
      The largest allocation size that will be allocated from a pool is
      <inlineequation><mathphrase>2<superscript>22</superscript></mathphrase></inlineequation>
      when <inlineequation><mathphrase>S > 20</mathphrase></inlineequation>,
      otherwise 3072 when <inlineequation><mathphrase>S > 16</mathphrase></inlineequation>,
      otherwise 768.
   </para>

   <para>
      <emphasis>23.12.6.1 [memory.resource.monotonic.buffer.ctor]</emphasis>
      The default <code>next_buffer_size</code> is <code>128 * sizeof(void*)</code>.
      The default growth factor is <code>1.5</code>.
   </para>

   <para>
      <emphasis>23.15.4.3 [meta.unary.prop]</emphasis>
      The predicate condition for
      <code>has_unique_object_representations</code> is true for all scalar
      types except floating point types.
   </para>

   <para>
      <emphasis>23.19.3 [execpol.type],
      28.4.3 [algorithms.parallel.exec]</emphasis>
      There are no implementation-defined execution policies.
   </para>

   <para>
      <emphasis>24.4.2 [string.view.template]</emphasis>
      <classname>basic_string_view&lt;C, T&gt;::iterator</classname> is
      <code>C*</code> and
      <classname>basic_string_view&lt;C, T&gt;::const_iterator</classname> is
      <code>const C*</code>.
   </para>


   <para>
      <emphasis>28.4.3 [algorithms.parallel.exec]</emphasis>
      Threads of execution created by <classname>std::thread</classname>
      provide concurrent forward progress guarantees, so threads of execution
      implicitly created by the library will provide parallel forward
      progress guarantees.
   </para>

   <para>
      <emphasis>29.4.1 [cfenv.syn]</emphasis>
      The effects of the <filename>&lt;cfenv&gt;</filename> functions
      depends on whether the <code>FENV_ACCESS</code> pragma is supported,
      and on the C library that provides the header.
   </para>

   <para>
      <emphasis>29.6.9 [c.math.rand]</emphasis>
      Whether the <function>rand</function> function may introduce data
      races depends on the target C library that provides the function.
   </para>

   <para>
      <emphasis>29.9.5 [sf.cmath]</emphasis>
      The effect of calling the mathematical special functions with large
      inputs should be documented here.
   </para>

   <para>
      <emphasis>30.10.2.1 [fs.conform.9945]</emphasis>
      The behavior of the filesystem library implementation will depend on
      the target operating system. Some features will not be supported
      on some targets.
   </para>

   <para>
      <emphasis>30.10.5 [fs.filesystem.syn]</emphasis>
      The clock used for file times is an unspecified type
      with a signed 64-bit representation, capable of representing
      timestamps with nanosecond resolution. The clock's epoch is
      unspecified, but is not the same as the system clock's epoch.
   </para>

   <para>
      <emphasis>30.10.7.1 [fs.path.generic]</emphasis>
      dot-dot in the root-directory refers to the root-directory itself.
      On Windows, a drive specifier such as <code>"C:"</code> or
      <code>"z:"</code> is treated as a root-name. On Cygwin, a path
      that begins with two successive directory separators is a
      root-name. Otherwise (for POSIX-like systems other than Cygwin),
      the implementation-defined root-name is an unspecified string
      which does not appear in any pathnames.
   </para>

   <para>
      <emphasis>30.10.10.1 [fs.enum.path.format]</emphasis>
      The character sequence is always interpreted in the native pathname
      format.
   </para>

   <para>
      <emphasis>30.10.15.4 [fs.op.file_size]</emphasis>
      If <code>!is_regular_file(p)</code>, an error is reported.
   </para>


</section>

</section>
