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<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Clang - C++20, C++17, C++14, C++11 and C++98 Status</title>
<link type="text/css" rel="stylesheet" href="menu.css">
<link type="text/css" rel="stylesheet" href="content.css">
<style type="text/css">
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<body>
<!--#include virtual="menu.html.incl"-->
<div id="content">
<!--*************************************************************************-->
<h1>C++ Support in Clang</h1>
<!--*************************************************************************-->
<p>Clang fully implements all published ISO C++ standards
(<a href="#cxx98">C++98 / C++03</a>,
<a href="#cxx11">C++11</a>,
<a href="#cxx14">C++14</a>, and
<a href="#cxx17">C++17</a>), and some of the upcoming <a
href="#cxx20">C++20</a> standard.
<p>The Clang community is continually striving to improve C++ standards
compliance between releases by submitting and tracking <a
href="cxx_dr_status.html">C++ Defect Reports</a> and implementing resolutions
as they become available.</p>
<p>Experimental work is also under way to implement <a href="#ts">C++ Technical
Specifications</a> that will help drive the future of the C++ programming
language.</p>
<p>The <a href="https://bugs.llvm.org/">LLVM bug tracker</a> contains Clang
C++ components that track known bugs with Clang's language conformance in
each language mode.</p>
<h2 id="cxx98">C++98 implementation status</h2>
<p>Clang implements all of the ISO C++ 1998 standard
(including the defects addressed in the ISO C++ 2003 standard)
except for <tt>export</tt> (which was removed in C++11).
<h2 id="cxx11">C++11 implementation status</h2>
<p>Clang 3.3 and later implement all of the <a
href="https://www.iso.org/standard/50372.html">ISO
C++ 2011 standard</a>.
<p>By default, Clang builds C++ code according to the C++98 standard, with many
C++11 features accepted as extensions. You can use Clang in C++11 mode with the
<code>-std=c++11</code> option. Clang's C++11 mode can be used
with <a href="https://libcxx.llvm.org/">libc++</a> or with gcc's libstdc++.
<details>
<summary>List of features and minimum Clang version with support</summary>
<table width="689" border="1" cellspacing="0">
<tr>
<th>Language Feature</th>
<th>C++11 Proposal</th>
<th>Available in Clang?</th>
</tr>
<tr>
<td rowspan="2">Rvalue references</td>
<td><a href="https://wg21.link/n2118">N2118</a></td>
<td class="full" align="center">Clang 2.9</td>
<tr> <!-- from Kona 2019-->
<td><a href="https://wg21.link/p1825r0">P1825R0</a> (<a href="#dr">DR</a>)</td>
<td class="none" align="center">No</td>
</tr>
</tr>
<tr>
<td> Rvalue references for <code>*this</code></td>
<td><a href="https://wg21.link/n2439">N2439</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Initialization of class objects by rvalues</td>
<td><a href="https://wg21.link/n1610">N1610</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Non-static data member initializers</td>
<td><a href="https://wg21.link/n2756">N2756</a></td>
<td class="full" align="center">Clang 3.0</td>
</tr>
<tr>
<td>Variadic templates</td>
<td><a href="https://wg21.link/n2242">N2242</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td> Extending variadic template template parameters</td>
<td><a href="https://wg21.link/n2555">N2555</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td rowspan="3">Initializer lists</td>
<td><a href="https://wg21.link/n2672">N2672</a></td>
<td class="full" align="center">Clang 3.1</td>
</tr>
<tr> <!-- from Kona 2019-->
<td><a href="https://wg21.link/p1009r2">P1009R2</a> (<a href="#dr">DR</a>)</td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr> <!-- from Prague-->
<td><a href="https://wg21.link/p1957r2">P1957R2</a> (<a href="#dr">DR</a>)</td>
<td class="unreleased" align="center">Clang 11</td>
</tr>
<tr>
<td>Static assertions</td>
<td><a href="https://wg21.link/n1720">N1720</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td><code>auto</code>-typed variables</td>
<td><a href="https://wg21.link/n1984">N1984</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td> Multi-declarator <code>auto</code></td>
<td><a href="https://wg21.link/n1737">N1737</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td> Removal of auto as a storage-class specifier</td>
<td><a href="https://wg21.link/n2546">N2546</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td> New function declarator syntax</td>
<td><a href="https://wg21.link/n2541">N2541</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td rowspan="2">Lambda expressions</td>
<td><a href="https://wg21.link/n2927">N2927</a></td>
<td class="full" align="center">Clang 3.1</td>
</tr>
<tr>
<!-- from Albuquerque 2017 -->
<td><a href="https://wg21.link/p0588r1">P0588R1</a> (<a href="#dr">DR</a>)</td>
<td class="none" align="center">No</td>
</tr>
<tr>
<td>Declared type of an expression</td>
<td><a href="https://wg21.link/n2343">N2343</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td> Incomplete return types</td>
<td><a href="https://wg21.link/n3276">N3276</a></td>
<td class="full" align="center">Clang 3.1</td>
</tr>
<tr>
<td>Right angle brackets</td>
<td><a href="https://wg21.link/n1757">N1757</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Default template arguments for function templates</td>
<td><a href="https://wg21.link/cwg226">DR226</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Solving the SFINAE problem for expressions</td>
<td><a href="https://wg21.link/n2634">DR339</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Alias templates</td>
<td><a href="https://wg21.link/n2258">N2258</a></td>
<td class="full" align="center">Clang 3.0</td>
</tr>
<tr>
<td>Extern templates</td>
<td><a href="https://wg21.link/n1987">N1987</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Null pointer constant</td>
<td><a href="https://wg21.link/n2431">N2431</a></td>
<td class="full" align="center">Clang 3.0</td>
</tr>
<tr>
<td>Strongly-typed enums</td>
<td><a href="https://wg21.link/n2347">N2347</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Forward declarations for enums</td>
<td><a href="https://wg21.link/n2764">N2764</a>
<br><a href="https://wg21.link/cwg1206">DR1206</a></td>
<td class="full" align="center">Clang 3.1</td>
</tr>
<tr>
<td>Standardized attribute syntax</td>
<td><a href="https://wg21.link/n2761">N2761</a></td>
<td class="full" align="center">Clang 3.3 <a href="#n2761">(1)</a></td>
</tr>
<tr>
<td rowspan="2">Generalized constant expressions</td>
<td><a href="https://wg21.link/n2235">N2235</a></td>
<td class="full" align="center">Clang 3.1</td>
</tr>
<tr>
<!-- from Albuquerque 2017 -->
<td><a href="https://wg21.link/p0859r0">P0859R0</a> (<a href="#dr">DR</a>)</td>
<td class="full" align="center">Clang 8</td>
</tr>
<tr>
<td>Alignment support</td>
<td><a href="https://wg21.link/n2341">N2341</a></td>
<td class="full" align="center">Clang 3.3</td>
</tr>
<tr>
<td>Conditionally-support behavior</td>
<td><a href="https://wg21.link/n1627">N1627</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Changing undefined behavior into diagnosable errors</td>
<td><a href="https://wg21.link/n1727">N1727</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Delegating constructors</td>
<td><a href="https://wg21.link/n1986">N1986</a></td>
<td class="full" align="center">Clang 3.0</td>
</tr>
<tr>
<td rowspan="2">Inheriting constructors</td>
<td><a href="https://wg21.link/n2540">N2540</a></td>
<td class="full" align="center">Clang 3.3</td>
</tr>
<tr>
<!-- from Kona 2015 -->
<td><a href="https://wg21.link/p0136r1">P0136R1</a> (<a href="#dr">DR</a>)</td>
<td class="full" align="center">Clang 3.9</td>
</tr>
<tr>
<td>Explicit conversion operators</td>
<td><a href="https://wg21.link/n2437">N2437</a></td>
<td class="full" align="center">Clang 3.0</td>
</tr>
<tr>
<td>New character types</td>
<td><a href="https://wg21.link/n2249">N2249</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Unicode string literals</td>
<td><a href="https://wg21.link/n2442">N2442</a></td>
<td class="full" align="center">Clang 3.0</td>
</tr>
<tr>
<td>Raw string literals</td>
<td><a href="https://wg21.link/n2442">N2442</a></td>
<td class="full" align="center">Clang 3.0</td>
</tr>
<tr>
<td>Universal character names in literals</td>
<td><a href="https://wg21.link/n2170">N2170</a></td>
<td class="full" align="center">Clang 3.1</td>
</tr>
<tr>
<td>User-defined literals</td>
<td><a href="https://wg21.link/n2765">N2765</a></td>
<td class="full" align="center">Clang 3.1</td>
</tr>
<tr>
<td>Standard Layout Types</td>
<td><a href="https://wg21.link/n2342">N2342</a></td>
<td class="full" align="center">Clang 3.0</td>
</tr>
<tr>
<td rowspan="2">Defaulted functions</td>
<td><a href="https://wg21.link/n2346">N2346</a></td>
<td class="full" align="center">Clang 3.0</td>
</tr>
<tr> <!-- from Kona 2019-->
<td><a href="https://wg21.link/p1286r2">P1286R2</a> (<a href="#dr">DR</a>)</td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr>
<td>Deleted functions</td>
<td><a href="https://wg21.link/n2346">N2346</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Extended friend declarations</td>
<td><a href="https://wg21.link/n1791">N1791</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Extending <code>sizeof</code></td>
<td><a href="https://wg21.link/n2253">N2253</a>
<br><a href="https://wg21.link/cwg850">DR850</a></td>
<td class="full" align="center">Clang 3.1</td>
</tr>
<tr>
<td>Inline namespaces</td>
<td><a href="https://wg21.link/n2535">N2535</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Unrestricted unions</td>
<td><a href="https://wg21.link/n2544">N2544</a></td>
<td class="full" align="center">Clang 3.1</td>
</tr>
<tr>
<td>Local and unnamed types as template arguments</td>
<td><a href="https://wg21.link/n2657">N2657</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td rowspan="2">Range-based for</td>
<td><a href="https://wg21.link/n2930">N2930</a></td>
<td class="full" align="center">Clang 3.0</td>
</tr>
<tr>
<!-- from Jacksonville 2018 -->
<td><a href="https://wg21.link/p0962r1">P0962R1</a> (<a href="#dr">DR</a>)</td>
<td class="full" align="center">Clang 8</td>
</tr>
<tr>
<td>Explicit virtual overrides</td>
<td><a href="https://wg21.link/n2928">N2928</a>
<br><a href="https://wg21.link/n3206">N3206</a>
<br><a href="https://wg21.link/n3272">N3272</a></td>
<td class="full" align="center">Clang 3.0</td>
</tr>
<tr>
<td>Minimal support for garbage collection and reachability-based leak detection</td>
<td><a href="https://wg21.link/n2670">N2670</a></td>
<td class="na" align="center">N/A <a href="#n2670">(2)</a></td>
</tr>
<tr>
<td>Allowing move constructors to throw [noexcept]</td>
<td><a href="https://wg21.link/n3050">N3050</a></td>
<td class="full" align="center">Clang 3.0</td>
</tr>
<tr>
<td>Defining move special member functions</td>
<td><a href="https://wg21.link/n3053">N3053</a></td>
<td class="full" align="center">Clang 3.0</td>
</tr>
<tr class="separator">
<th align="center" colspan="3">Concurrency</th>
</tr>
<tr>
<td>Sequence points</td>
<td><a href="https://wg21.link/n2239">N2239</a></td>
<td class="full" align="center">Clang 3.3</td>
</tr>
<tr>
<td>Atomic operations</td>
<td><a href="https://wg21.link/n2427">N2427</a></td>
<td class="full" align="center">Clang 3.1</td>
</tr>
<tr>
<td>Strong Compare and Exchange</td>
<td><a href="https://wg21.link/n2748">N2748</a></td>
<td class="full" align="center">Clang 3.1 <a href="#n2748">(3)</a></td>
</tr>
<tr>
<td>Bidirectional Fences</td>
<td><a href="https://wg21.link/n2752">N2752</a></td>
<td class="full" align="center">Clang 3.1</td>
</tr>
<tr>
<td>Memory model</td>
<td><a href="https://wg21.link/n2429">N2429</a></td>
<td class="full" align="center">Clang 3.2</td>
</tr>
<tr>
<td>Data-dependency ordering: atomics and memory model</td>
<td><a href="https://wg21.link/n2664">N2664</a></td>
<td class="full" align="center">Clang 3.2 <a href="#n2664">(4)</a></td>
</tr>
<tr>
<td>Propagating exceptions</td>
<td><a href="https://wg21.link/n2179">N2179</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Allow atomics use in signal handlers</td>
<td><a href="https://wg21.link/n2547">N2547</a></td>
<td class="full" align="center">Clang 3.1</td>
</tr>
<tr>
<td>Thread-local storage</td>
<td><a href="https://wg21.link/n2659">N2659</a></td>
<td class="full" align="center">Clang 3.3 <a href="#n2659">(5)</a></td>
</tr>
<tr>
<td>Dynamic initialization and destruction with concurrency</td>
<td><a href="https://wg21.link/n2660">N2660</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr class="separator">
<th align="center" colspan="3">C99 Features in C++11</th>
</tr>
<tr>
<td><code>__func__</code> predefined identifier</td>
<td><a href="https://wg21.link/n2340">N2340</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>C99 preprocessor</td>
<td><a href="https://wg21.link/n1653">N1653</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td><code>long long</code></td>
<td><a href="https://wg21.link/n1811">N1811</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>Extended integral types</td>
<td><a href="https://wg21.link/n1988">N1988</a></td>
<td class="na" align="center">N/A <a href="#n1988">(6)</a></td>
</tr>
</table>
<p>
<span id="n2761">(1): The <code>[[carries_dependency]]</code> attribute
has no effect.</span><br>
<span id="n2670">(2): No compiler changes are required for an implementation
such as Clang that does not provide garbage collection.</span><br>
<span id="n2748">(3): All compare-exchange operations are emitted as
strong compare-exchanges.</span><br>
<span id="n2664">(4): <code>memory_order_consume</code> is lowered to
<code>memory_order_acquire</code>.</span><br>
<span id="n2659">(5): <code>thread_local</code> support
requires a C++ runtime library providing <code>__cxa_thread_atexit</code>, such
as <a href="https://libcxxabi.llvm.org">libc++abi</a> 3.6 or later,
or libsupc++ 4.8 or later.</span><br>
<span id="n1988">(6): No compiler changes are required for an implementation
such as Clang that does not provide any extended integer types.
<code>__int128</code> is not treated as an extended integer type,
because changing <code>intmax_t</code> would be an ABI-incompatible
change.</span>
</p>
</details>
<h2 id="cxx14">C++14 implementation status</h2>
<p>Clang 3.4 and later implement all of the <a
href="https://www.iso.org/standard/64029.html">ISO
C++ 2014 standard</a>.
<p>You can use Clang in C++14 mode with the <code>-std=c++14</code> option
(use <code>-std=c++1y</code> in Clang 3.4 and earlier).</p>
<details>
<summary>List of features and minimum Clang version with support</summary>
<table width="689" border="1" cellspacing="0">
<tr>
<th>Language Feature</th>
<th>C++14 Proposal</th>
<th>Available in Clang?</th>
</tr>
<tr>
<td>Tweak to certain C++ contextual conversions</td>
<td><a href="https://wg21.link/n3323">N3323</a></td>
<td class="full" align="center">Clang 3.4</td>
</tr>
<tr>
<td>Binary literals</td>
<td><a href="https://wg21.link/n3472">N3472</a></td>
<td class="full" align="center">Clang 2.9</td>
</tr>
<tr>
<td>decltype(auto)</td>
<td rowspan=2 style="vertical-align:middle"><a href="https://wg21.link/n3638">N3638</a></td>
<td class="full" align="center">Clang 3.3</td>
</tr>
<tr>
<td>Return type deduction for normal functions</td>
<td class="full" align="center">Clang 3.4</td>
</tr>
<tr>
<td>Initialized lambda captures</td>
<td><a href="https://wg21.link/n3648">N3648</a></td>
<td class="full" align="center">Clang 3.4</td>
</tr>
<tr>
<td>Generic lambdas</td>
<td><a href="https://wg21.link/n3649">N3649</a></td>
<td class="full" align="center">Clang 3.4</td>
</tr>
<tr>
<td>Variable templates</td>
<td><a href="https://wg21.link/n3651">N3651</a></td>
<td class="full" align="center">Clang 3.4</td>
</tr>
<tr>
<td>Relaxing requirements on constexpr functions</td>
<td><a href="https://wg21.link/n3652">N3652</a></td>
<td class="full" align="center">Clang 3.4</td>
</tr>
<tr>
<td>Member initializers and aggregates</td>
<td><a href="https://wg21.link/n3653">N3653</a></td>
<td class="full" align="center">Clang 3.3</td>
</tr>
<tr>
<td>Clarifying memory allocation</td>
<td><a href="https://wg21.link/n3664">N3664</a></td>
<td class="full" align="center">Clang 3.4</td>
</tr>
<tr>
<td><tt>[[deprecated]]</tt> attribute</td>
<td><a href="https://wg21.link/n3760">N3760</a></td>
<td class="full" align="center">Clang 3.4</td>
</tr>
<tr>
<td>Single quotation mark as digit separator</td>
<td><a href="https://wg21.link/n3781">N3781</a></td>
<td class="full" align="center">Clang 3.4</td>
</tr>
<tr>
<td>C++ Sized Deallocation</td>
<td><a href="https://wg21.link/n3778">N3778</a></td>
<td class="full" align="center">Clang 3.4 <a href="#n3778">(7)</a></td>
</tr>
</table>
<p>
<span id="n3778">(7): In Clang 3.7 and later, sized deallocation is only enabled
if the user passes the <code>-fsized-deallocation</code> flag. The user must
supply definitions of the sized deallocation functions, either by providing them
explicitly or by using a C++ standard library that does. <code>libstdc++</code>
added these functions in version 5.0, and <code>libc++</code> added them in
version 3.7.
</span>
</p>
</details>
<h2 id="cxx17">C++17 implementation status</h2>
<p>Clang 5 and later implement all the features of the
<a href="https://www.iso.org/standard/68564.html">ISO C++ 2017 standard</a>.
<p>You can use Clang in C++17 mode with the <code>-std=c++17</code> option
(use <code>-std=c++1z</code> in Clang 4 and earlier).</p>
<details open>
<summary>List of features and minimum Clang version with support</summary>
<table width="689" border="1" cellspacing="0">
<tr>
<th>Language Feature</th>
<th>C++17 Proposal</th>
<th>Available in Clang?</th>
</tr>
<!-- Issaquah 2014 papers -->
<tr>
<td><tt>static_assert</tt> with no message</td>
<td><a href="https://wg21.link/n3928">N3928</a></td>
<td class="full" align="center">Clang 3.5</td>
</tr>
<!-- Rapperswil papers -->
<tr>
<td>Disabling trigraph expansion by default</td>
<td><a href="https://wg21.link/n4086">N4086</a></td>
<td class="full" align="center">Clang 3.5</td>
</tr>
<tr>
<td><tt>typename</tt> in a template template parameter</td>
<td><a href="https://wg21.link/n4051">N4051</a></td>
<td class="full" align="center">Clang 3.5</td>
</tr>
<tr>
<td>New <tt>auto</tt> rules for direct-list-initialization
<td><a href="https://wg21.link/n3922">N3922</a></td>
<td class="full" align="center">Clang 3.8 <a href="#n3922">(8)</a></td>
</tr>
<!-- Urbana papers -->
<tr>
<td rowspan="2">Fold expressions</td>
<td><a href="https://wg21.link/n4295">N4295</a></td>
<td class="full" align="center">Clang 3.6</td>
</tr>
<tr> <!-- from Jacksonville -->
<td><a href="https://wg21.link/p0036r0">P0036R0</a></td>
<td class="full" align="center">Clang 3.9</td>
</tr>
<tr>
<td><tt>u8</tt> character literals</td>
<td><a href="https://wg21.link/n4267">N4267</a></td>
<td class="full" align="center">Clang 3.6</td>
</tr>
<tr>
<td>Nested namespace definition</td>
<td><a href="https://wg21.link/n4230">N4230</a></td>
<td class="full" align="center">Clang 3.6</td>
</tr>
<tr>
<td>Attributes for namespaces and enumerators</td>
<td><a href="https://wg21.link/n4266">N4266</a></td>
<td class="full" align="center">Clang 3.6</td>
</tr>
<tr>
<td>Allow constant evaluation for all non-type template arguments</td>
<td><a href="https://wg21.link/n4268">N4268</a></td>
<td class="full" align="center">Clang 3.6</td>
</tr>
<!-- Kona papers -->
<tr>
<td>Remove deprecated <tt>register</tt> storage class</td>
<td><a href="https://wg21.link/p0001r1">P0001R1</a></td>
<td class="full" align="center">Clang 3.8</td>
</tr>
<tr>
<td>Remove deprecated <tt>bool</tt> increment</td>
<td><a href="https://wg21.link/p0002r1">P0002R1</a></td>
<td class="full" align="center">Clang 3.8</td>
</tr>
<tr>
<td>Make exception specifications part of the type system</td>
<td><a href="https://wg21.link/p0012r1">P0012R1</a></td>
<td class="full" align="center">Clang 4</td>
</tr>
<tr>
<td><tt>__has_include</tt> in preprocessor conditionals</td>
<td><a href="https://wg21.link/p0061r1">P0061R1</a></td>
<td class="full" align="center">Yes</td>
</tr>
<!-- Jacksonville papers -->
<tr>
<td><tt>[[fallthrough]]</tt> attribute</td>
<td><a href="https://wg21.link/p0188r1">P0188R1</a></td>
<td class="full" align="center">Clang 3.9</td>
</tr>
<tr>
<td rowspan="2"><tt>[[nodiscard]]</tt> attribute</td>
<td><a href="https://wg21.link/p0189r1">P0189R1</a></td>
<td class="full" align="center">Clang 3.9</td>
</tr>
<tr> <!-- from Cologne 2019 -->
<td><a href="https://wg21.link/p1771r1">P1771R1</a> (<a href="#dr">DR</a>)</td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr>
<td><tt>[[maybe_unused]]</tt> attribute</td>
<td><a href="https://wg21.link/p0212r1">P0212R1</a></td>
<td class="full" align="center">Clang 3.9</td>
</tr>
<tr>
<td>Aggregate initialization of classes with base classes</td>
<td><a href="https://wg21.link/p0017r1">P0017R1</a></td>
<td class="full" align="center">Clang 3.9</td>
</tr>
<tr>
<td><tt>constexpr</tt> lambda expressions</td>
<td><a href="https://wg21.link/p0170r1">P0170R1</a></td>
<td class="full" align="center">Clang 5</td>
</tr>
<tr>
<td>Differing <tt>begin</tt> and <tt>end</tt> types in range-based <tt>for</tt></td>
<td><a href="https://wg21.link/p0184r0">P0184R0</a></td>
<td class="full" align="center">Clang 3.9</td>
</tr>
<tr>
<td>Lambda capture of <tt>*this</tt></td>
<td><a href="https://wg21.link/p0018r3">P0018R3</a></td>
<td class="full" align="center">Clang 3.9</td>
</tr>
<tr>
<td>Direct-list-initialization of <tt>enum</tt>s</td>
<td><a href="https://wg21.link/p0138r2">P0138R2</a></td>
<td class="full" align="center">Clang 3.9</td>
</tr>
<tr>
<td>Hexadecimal floating-point literals</td>
<td><a href="https://wg21.link/p0245r1">P0245R1</a></td>
<td class="full" align="center">Yes</td>
</tr>
<!-- Oulu papers -->
<tr>
<td>Using attribute namespaces without repetition</td>
<td><a href="https://wg21.link/p0028r4">P0028R4</a></td>
<td class="full" align="center">Clang 3.9</td>
</tr>
<tr>
<td>Dynamic memory allocation for over-aligned data</td>
<td><a href="https://wg21.link/p0035r4">P0035R4</a></td>
<td class="full" align="center">Clang 4</td>
</tr>
<tr>
<td rowspan="4">Template argument deduction for class templates</td>
<td><a href="https://wg21.link/p0091r3">P0091R3</a></td>
<td rowspan="2" class="full" align="center">Clang 5</td>
</tr>
<tr> <!-- from Issaquah -->
<td><a href="https://wg21.link/p0512r0">P0512R0</a></td>
</tr>
<tr>
<!-- from Kona 2017 -->
<td><a href="https://wg21.link/p0620r1">P0620R0</a> (<a href="#dr">DR</a>)</td>
<td class="full" align="center">Clang 7</td>
</tr>
<tr>
<!-- from Toronto 2017 -->
<td><a href="https://wg21.link/p0702r1">P0702R1</a> (<a href="#dr">DR</a>)</td>
<td class="full" align="center">Clang 6</td>
</tr>
<tr>
<td>Non-type template parameters with <tt>auto</tt> type</td>
<td><a href="https://wg21.link/p0127r2">P0127R2</a></td>
<td class="full" align="center">Clang 4</td>
</tr>
<tr>
<td>Guaranteed copy elision</td>
<td><a href="https://wg21.link/p0135r1">P0135R1</a></td>
<td class="full" align="center">Clang 4</td>
</tr>
<tr>
<td rowspan=2>Stricter expression evaluation order</td>
<td><a href="https://wg21.link/p0145r3">P0145R3</a></td>
<td class="full" align="center" rowspan=2>Clang 4 <a href="#p0145">(9)</a></td>
</tr>
<tr>
<td><a href="https://wg21.link/p0400r0">P0400R0</a></td>
</tr>
<tr>
<td>Requirement to ignore unknown attributes</td>
<td><a href="https://wg21.link/p0283r2">P0283R2</a></td>
<td class="full" align="center">Yes</td>
</tr>
<tr>
<td><tt>constexpr</tt> <em>if-statement</em>s</td>
<td><a href="https://wg21.link/p0292r2">P0292R2</a></td>
<td class="full" align="center">Clang 3.9</td>
</tr>
<tr>
<td>Inline variables</td>
<td><a href="https://wg21.link/p0386r2">P0386R2</a></td>
<td class="full" align="center">Clang 3.9</td>
</tr>
<tr>
<td rowspan="3">Structured bindings</td>
<td><a href="https://wg21.link/p0217r3">P0217R3</a></td>
<td class="full" align="center">Clang 4</td>
</tr>
<tr>
<!-- from Jacksonville 2018 -->
<td><a href="https://wg21.link/p0961r1">P0961R1</a> (<a href="#dr">DR</a>)</td>
<td class="full" align="center">Clang 8</td>
</tr>
<tr>
<!-- from Jacksonville 2018 -->
<td><a href="https://wg21.link/p0969r0">P0969R0</a> (<a href="#dr">DR</a>)</td>
<td class="full" align="center">Clang 8</td>
</tr>
<tr>
<td>Separate variable and condition for <tt>if</tt> and <tt>switch</tt></td>
<td><a href="https://wg21.link/p0305r1">P0305R1</a></td>
<td class="full" align="center">Clang 3.9</td>
</tr>
<!-- Issaquah 2016 papers -->
<tr>
<td>Matching template template parameters to compatible arguments</td>
<td><a href="https://wg21.link/p0522r0">P0522R0</a></td>
<td class="partial" align="center">Partial <a href="#p0522">(10)</a></td>
</tr>
<tr>
<td>Removing deprecated dynamic exception specifications</td>
<td><a href="https://wg21.link/p0003r5">P0003R5</a></td>
<td class="full" align="center">Clang 4</td>
</tr>
<tr>
<td>Pack expansions in <em>using-declarations</em></td>
<td><a href="https://wg21.link/p0195r2">P0195R2</a></td>
<td class="full" align="center">Clang 4</td>
</tr>
</table>
<p>
<span id="n3922">(8): This is a backwards-incompatible change that is applied to
all language versions that allow type deduction from <tt>auto</tt>
(per the request of the C++ committee).
In Clang 3.7, a warning is emitted for all cases that would change meaning.
</span><br>
<span id="p0145">(9): Under the MS ABI, function parameters are destroyed from
left to right in the callee. As a result, function parameters in calls to
<tt>operator<<</tt>, <tt>operator>></tt>, <tt>operator->*</tt>,
<tt>operator&&</tt>, <tt>operator||</tt>, and <tt>operator,</tt>
functions using expression syntax are no longer guaranteed to be destroyed in
reverse construction order in that ABI.
This is not fully supported during constant expression evaluation until Clang 12.
</span><br>
<span id="p0522">(10): Despite being the resolution to a Defect Report, this
feature is disabled by default in all language versions, and can be enabled
explicitly with the flag <tt>-frelaxed-template-template-args</tt> in Clang 4
onwards.
The change to the standard lacks a corresponding change for template partial
ordering, resulting in ambiguity errors for reasonable and previously-valid
code. This issue is expected to be rectified soon.
</span>
</p>
</details>
<h2 id="cxx20">C++20 implementation status</h2>
<p>Clang has support for some of the features of the
ISO C++ 2020 Draft International Standard.
<p>You can use Clang in C++20 mode with the <code>-std=c++20</code> option
(use <code>-std=c++2a</code> in Clang 9 and earlier).</p>
<details open>
<summary>List of features and minimum Clang version with support</summary>
<table width="689" border="1" cellspacing="0">
<tr>
<th>Language Feature</th>
<th>C++20 Proposal</th>
<th>Available in Clang?</th>
</tr>
<!-- Toronto 2017 papers -->
<tr>
<td>Default member initializers for bit-fields</td>
<td><a href="https://wg21.link/p0683r1">P0683R1</a></td>
<td class="full" align="center">Clang 6</td>
</tr>
<tr>
<td><tt>const&</tt>-qualified pointers to members</td>
<td><a href="https://wg21.link/p0704r1">P0704R1</a></td>
<td class="full" align="center">Clang 6</td>
</tr>
<tr>
<td>Allow <i>lambda-capture</i> <tt>[=, this]</tt></td>
<td><a href="https://wg21.link/p0409r2">P0409R2</a></td>
<td class="full" align="center">Clang 6</td>
</tr>
<tr>
<td rowspan="2"><tt>__VA_OPT__</tt> for preprocessor comma elision</td>
<td><a href="https://wg21.link/p0306r4">P0306R4</a></td>
<td class="full" align="center">Clang 6</td>
</tr>
<tr> <!-- from Rapperswil -->
<td><a href="https://wg21.link/p1042r1">P1042R1</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr>
<td>Designated initializers</td>
<td><a href="https://wg21.link/p0329r4">P0329R4</a></td>
<td class="full" align="center">Clang 10</td>
</tr>
<tr>
<td><i>template-parameter-list</i> for generic lambdas</td>
<td><a href="https://wg21.link/p0428r2">P0428R2</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr id="p0734">
<td rowspan="12">Concepts</td>
<td><a href="https://wg21.link/p0734r0">P0734R0</a></td>
<td rowspan="4" class="full" align="center">Clang 10</td>
</tr>
<tr> <!-- from Albuquerque -->
<td><a href="https://wg21.link/p0857r0">P0857R0</a></td>
</tr>
<tr> <!-- from San Diego -->
<td><a href="https://wg21.link/p1084r2">P1084R2</a></td>
</tr>
<tr>
<td><a href="https://wg21.link/p1141r2">P1141R2</a></td>
</tr>
<tr> <!-- from Cologne -->
<td><a href="https://wg21.link/p0848r3">P0848R3</a></td>
<td rowspan="1" class="none" align="center">No</td>
</tr>
<tr>
<td><a href="https://wg21.link/p1616r1">P1616R1</a></td>
<td rowspan="2" class="full" align="center">Clang 10</td>
</tr>
<tr>
<td><a href="https://wg21.link/p1452r2">P1452R2</a></td>
</tr>
<tr> <!-- from Belfast -->
<td><a href="https://wg21.link/p1972r0">P1972R0</a></td>
<td rowspan="2" class="none" align="center">No</td>
</tr>
<tr>
<td><a href="https://wg21.link/p1980r0">P1980R0</a></td>
</tr>
<tr> <!-- from Prague -->
<td><a href="https://wg21.link/p2103r0">P2103R0</a></td>
<td rowspan="3" class="none" align="center">No</td>
</tr>
<tr>
<td><a href="https://wg21.link/p2092r0">P2092R0</a></td>
</tr>
<tr>
<td><a href="https://wg21.link/p2113r0">P2113R0</a></td>
</tr>
<!-- Albuquerque papers -->
<tr>
<td>Range-based for statements with initializer</td>
<td><a href="https://wg21.link/p0614r1">P0614R1</a></td>
<td class="full" align="center">Clang 8</td>
</tr>
<tr>
<td>ADL and function templates that are not visible</td>
<td><a href="https://wg21.link/p0846r0">P0846R0</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr>
<td><tt>const</tt> mismatch with defaulted copy constructor</td>
<td><a href="https://wg21.link/p0641r2">P0641R2</a></td>
<td class="full" align="center">Clang 8</td>
</tr>
<tr>
<td rowspan="10">Consistent comparison (<tt>operator<=></tt>)</td>
<td><a href="https://wg21.link/p0515r3">P0515R3</a></td>
<td rowspan="8" class="full" align="center">Clang 10</td>
</tr>
<tr> <!-- from Jacksonville -->
<td><a href="https://wg21.link/p0905r1">P0905R1</a></td>
</tr>
<tr> <!-- from Rapperswil -->
<td><a href="https://wg21.link/p1120r0">P1120R0</a></td>
</tr>
<tr> <!-- from Kona 2019 -->
<td><a href="https://wg21.link/p1185r2">P1185R2</a></td>
</tr>
<tr> <!-- from Cologne -->
<td><a href="https://wg21.link/p1186r3">P1186R3</a></td>
</tr>
<tr>
<td><a href="https://wg21.link/p1630r1">P1630R1</a></td>
</tr>
<tr> <!-- from Belfast -->
<td><a href="https://wg21.link/p1946r0">P1946R0</a></td>
</tr>
<tr>
<td><a href="https://wg21.link/p1959r0">P1959R0</a></td>
</tr>
<tr> <!-- from Prague -->
<td><a href="https://wg21.link/p2002r1">P2002R1</a></td>
<td class="partial" align="center">Partial</td>
</tr>
<tr>
<td><a href="https://wg21.link/p2085r0">P2085R0</a></td>
<td class="none" align="center">No</td>
</tr>
<tr>
<td>Access checking on specializations</td>
<td><a href="https://wg21.link/p0692r1">P0692R1</a></td>
<td class="partial" align="center">Partial</td>
</tr>
<tr>
<td>Default constructible and assignable stateless lambdas</td>
<td><a href="https://wg21.link/p0624r2">P0624R2</a></td>
<td class="full" align="center">Clang 8</td>
</tr>
<tr>
<td>Lambdas in unevaluated contexts</td>
<td><a href="https://wg21.link/p0315r4">P0315R4</a></td>
<td class="none" align="center">No</td>
</tr>
<!-- Jacksonville papers -->
<tr>
<td><tt>[[no_unique_address]]</tt> attribute</td>
<td><a href="https://wg21.link/p0840r2">P0840R2</a></td>
<td class="full" align="center">Clang 9</td>
</tr>
<tr>
<td><tt>[[likely]]</tt> and <tt>[[unlikely]]</tt> attributes</td>
<td><a href="https://wg21.link/p0479r5">P0479R5</a></td>
<td class="unreleased" align="center">Clang 12</td>
</tr>
<tr>
<td><tt>typename</tt> optional in more contexts</td>
<td><a href="https://wg21.link/p0634r3">P0634R3</a></td>
<td class="none" align="center">No</td>
</tr>
<tr>
<td>Pack expansion in lambda <i>init-capture</i></td>
<td><a href="https://wg21.link/p0780r2">P0780R2</a></td>