I've reviewed all the C++ patches that have gone into GCC 12, and
documented the ones that seemed most interesting/relevant to our
users.
Additionally, I've also added links to the proposals/PRs/git commits
so that it's easier to find out more.
I've also updated our C++ DR table.
Validates, pushed.
---
htdocs/gcc-12/changes.html | 129 +++++++++++++++++++++++++----
htdocs/projects/cxx-dr-status.html | 10 +--
2 files changed, 119 insertions(+), 20 deletions(-)
base-commit: e8cffe6d8fa529066a3e012599f9f417ddf0e855
@@ -143,13 +143,19 @@ a work-in-progress.</p>
<h3 id="c-family">C family</h3>
<ul>
<li>Support for <code>__builtin_shufflevector</code> compatible with
- the clang language extension was added.
- </li>
+ the clang language extension was added.</li>
+ <li>Support for attribute <code>unavailable</code> was added.</li>
+ <li>A new built-in function, <code>__builtin_assoc_barrier</code>, was added.
+ It can be used to inhibit re-association of floating-point
+ expressions.</li>
<li>New warnings:
<ul>
<li><code>-Wbidi-chars</code> warns about potentially misleading UTF-8
- bidirectional control characters. The default is <code>-Wbidi-chars=unpaired</code>.
- </li>
+ bidirectional control characters. The default is
+ <code>-Wbidi-chars=unpaired</code>
+ (<a href="https://gcc.gnu.org/PR103026">PR103026</a>)</li>
+ <li><code>-Warray-compare</code> warns about comparisons between two operands of
+ array type (<a href="https://gcc.gnu.org/PR97573">PR97573</a>)</li>
</ul>
</li>
<li>Enhancements to existing warnings:
@@ -159,7 +165,8 @@ a work-in-progress.</p>
<code>-Wno-attributes=ns::</code> to suppress warnings about unknown scoped
attributes (in C++11 and C2X). Similarly,
<code>#pragma GCC diagnostic ignored_attributes "vendor::attr"</code> can
- be used to achieve the same effect.</li>
+ be used to achieve the same effect
+ (<a href="https://gcc.gnu.org/PR101940">PR101940</a>)</li>
</ul>
</li>
</ul>
@@ -168,23 +175,115 @@ a work-in-progress.</p>
<ul>
<li>Several C++23 features have been implemented:
<ul>
- <li>P1938R3, <code>if consteval</code></li>
- <li>P0849R8, <code>auto(x)</code>: decay-copy in the language</li>
- <li>P2242R3, Non-literal variables (and labels and gotos) in constexpr functions</li>
- <li>P2334R1, Support for preprocessing directives <code>elifdef</code> and
- <code>elifndef</code></li>
- <li>P2360R0, Extend <em>init-statement</em> to allow <em>alias-declaration</em></li>
- <li>DR 2397, <code>auto</code> specifier for pointers and references to arrays</li>
+ <li><a href="https://wg21.link/p1938">P1938R3</a>, <code>if consteval</code>
+ (<a href="https://gcc.gnu.org/PR100974">PR100974</a>)</li>
+ <li><a href="https://wg21.link/p0849">P0849R8</a>, <code>auto(x)</code>:
+ decay-copy in the language
+ (<a href="https://gcc.gnu.org/PR103049">PR103049</a>)</li>
+ <li><a href="https://wg21.link/p2242">P2242R3</a>, Non-literal variables (and
+ labels and gotos) in constexpr functions
+ (<a href="https://gcc.gnu.org/PR102612">PR102612</a>)</li>
+ <li><a href="https://wg21.link/p2334">P2334R1</a>, Support for preprocessing
+ directives <code>elifdef</code> and <code>elifndef</code>
+ (<a href="https://gcc.gnu.org/PR102616">PR102616</a>)</li>
+ <li><a href="https://wg21.link/p2360">P2360R0</a>, Extend <em>init-statement</em>
+ to allow <em>alias-declaration</em>
+ (<a href="https://gcc.gnu.org/PR102617">PR102617</a>)</li>
+ <!--
+ <li><a href="https://wg21.link/p2128">P2128R6</a>, Multidimensional subscript
+ operator</li>
+ -->
+ <li><a href="https://wg21.link/cwg2397">DR 2397</a>, <code>auto</code> specifier
+ for pointers and references to arrays
+ (<a href="https://gcc.gnu.org/PR100975">PR100975</a>)</li>
</ul>
</li>
<li>Several C++ Defect Reports have been resolved, e.g.:
<ul>
- <li>DR 1227, Mixing immediate and non-immediate contexts in deduction failure</li>
- <li>DR 2397, <code>auto</code> specifier for pointers and references to arrays</li>
+ <li><a href="https://wg21.link/cwg960">DR 960</a>, Covariant functions and
+ lvalue/rvalue references</li>
+ <li><a href="https://wg21.link/cwg1227">DR 1227</a>, Mixing immediate and
+ non-immediate contexts in deduction failure</li>
+ <li><a href="https://wg21.link/cwg1315">DR 1315</a>, Restrictions on non-type
+ template arguments in partial specializations</li>
+ <li><a href="https://wg21.link/cwg2082">DR 2082</a>, Referring to parameters
+ in unevaluated operands of default arguments</li>
+ <li><a href="https://wg21.link/cwg2351">DR 2351</a>, <code>void{}</code></li>
+ <li><a href="https://wg21.link/cwg2374">DR 2374</a>, Overly permissive
+ specification of <code>enum</code> direct-list-initialization</li>
+ <li><a href="https://wg21.link/cwg2397">DR 2397</a>, <code>auto</code> specifier
+ for pointers and references to arrays</li>
+ <li><a href="https://wg21.link/cwg2446">DR 2446</a>, Questionable type-dependency
+ of <em>concept-ids</em></li>
</ul>
</li>
+ <li>New command-line option <code>-fimplicit-constexpr</code> can be used to
+ make inline functions implicitly constexpr
+ (<a href="https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=87c2080b">git</a>)</li>
+ <li>Deduction guides can be declared at class scope
+ (<a href="https://gcc.gnu.org/PR79501">PR79501</a>)</li>
<li><code>-Wuninitialized</code> warns about using uninitialized variables in
- member initializer lists</li>
+ member initializer lists (<a href="https://gcc.gnu.org/PR19808">PR19808</a>)
+ </li>
+ <li><code>-Wint-in-bool-context</code> is now disabled when instantiating
+ a template (<a href="https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=3a2b12bc">git</a>)</li>
+ <li>Stricter checking of attributes on friend declarations: if a friend
+ declaration has an attribute, that declaration must be a definition.
+ Moreover, a C++11 attribute cannot appear in the middle of the
+ <em>decl-specifier-seq</em>.
+ (<a href="https://gcc.gnu.org/PR99032">PR99032</a>)</li>
+ <li>New warning options for C++ language mismatches:
+ <code>-Wc++11-extensions</code>, <code>-Wc++14-extensions</code>,
+ <code>-Wc++17-extensions</code>, <code>-Wc++20-extensions</code>,
+ and <code>-Wc++23-extensions</code>. They are enabled by default
+ and can be used to control existing pedwarns about occurences of
+ new C++ constructs in code using an old C++ standard dialect.</li>
+ <li>New warning <code>-Wmissing-requires</code> warns about missing
+ <code>requires</code>
+ (<a href="https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=e18e56c7">git</a>)</li>
+ <li>The existing <code>std::is_constant_evaluated</code> in <code>if</code>
+ warning was extended to warn in more cases
+ (<a href="https://gcc.gnu.org/PR100995">PR100995</a>)</li>
+ <li><code>-Waddress</code> has been enhanced so that it now warns about, for
+ instance, comparing the address of a nonstatic member function to null
+ (<a href="https://gcc.gnu.org/PR102103">PR102103</a>)</li>
+ <li>Errors about narrowing are no longer hidden if they occur in system
+ headers</li>
+ <li>Ordered comparison of null pointers is now rejected
+ (<a href="https://gcc.gnu.org/PR99701">PR99701</a>)</li>
+ <li>Anonymous structs with bases are now rejected
+ (<a href="https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=3ead06c1">git</a>)</li>
+ <li>The compiler rejects taking the address of an immediate member function
+ (<a href="https://gcc.gnu.org/PR102753">PR102753</a>)</li>
+ <li>The compiler has support for C++20
+ <code>__cpp_lib_is_pointer_interconvertible</code> and
+ <code>__cpp_lib_is_layout_compatible</code> to help the C++
+ library implement <a href="https://wg21.link/p0466">P0466</a>,
+ Layout-compatibility and Pointer-interconvertibility Traits
+ (<a href="https://gcc.gnu.org/PR101539">PR101539</a>)</li>
+ <li>Memory usage of constraint subsumption has been improved
+ (<a href="https://gcc.gnu.org/PR100828">PR100828</a>)</li>
+ <li><code>constinit thread_local</code> variables are optimized better
+ (<a href="https://gcc.gnu.org/PR101786">PR101786</a>)</li>
+ <li>Support for C++17 <code>std::hardware_destructive_interference_size</code>
+ was added, along with the <code>-Winterference-size</code> warning
+ (<a href="https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=76b75018">git</a>)</li>
+ <li>Many bugs in the CTAD handling have been fixed
+ (<a href="https://gcc.gnu.org/PR101344">PR101344</a>,
+ <a href="https://gcc.gnu.org/PR101883">PR101883</a>,
+ <a href="https://gcc.gnu.org/PR89062">PR89062</a>,
+ <a href="https://gcc.gnu.org/PR101233">PR101233</a>,
+ <a href="https://gcc.gnu.org/PR88252">PR88252</a>,
+ <a href="https://gcc.gnu.org/PR86439">PR86439</a>,
+ <a href="https://gcc.gnu.org/PR98832">PR98832</a>,
+ <a href="https://gcc.gnu.org/PR102933">PR102933</a> ...)</li>
+ <li>Several issues with constrained variable templates have been fixed
+ (<a href="https://gcc.gnu.org/PR98486">PR98486</a>)</li>
+ <li>The compiler performs less instantiating when doing speculative constant
+ evaluation
+ (<a href="https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=1595fe44">git</a>)</li>
+ <li>Various diagnostic improvements; e.g., a more precise caret location for
+ pointer-to-member expressions</li>
</ul>
<h4 id="libstdcxx">Runtime Library (libstdc++)</h4>
@@ -6749,7 +6749,7 @@
<td><a href="https://wg21.link/cwg960">960</a></td>
<td>CD2</td>
<td>Covariant functions and lvalue/rvalue references</td>
- <td class="unsupported">?</td>
+ <td class="supported">12</td>
<td></td>
</tr>
<tr>
@@ -9234,7 +9234,7 @@
<td><a href="https://wg21.link/cwg1315">1315</a></td>
<td>CD4</td>
<td>Restrictions on non-type template arguments in partial specializations</td>
- <td class="unsupported">?</td>
+ <td class="supported">12</td>
<td><a href="https://gcc.gnu.org/PR77781">PR77781</a></td>
</tr>
<tr>
@@ -16652,7 +16652,7 @@
<td><a href="https://wg21.link/cwg2374">2374</a></td>
<td>C++20</td>
<td>Overly permissive specification of <code>enum</code> direct-list-initialization</td>
- <td class="unsupported">?</td>
+ <td class="supported">12</td>
<td></td>
</tr>
<tr>
@@ -17156,7 +17156,7 @@
<td><a href="https://wg21.link/cwg2446">2446</a></td>
<td>C++20</td>
<td>Questionable type-dependency of <em>concept-ids</em></td>
- <td class="unsupported">?</td>
+ <td class="supported">12</td>
<td></td>
</tr>
<tr>
@@ -17492,7 +17492,7 @@
<p>This page is currently maintained by <a href="mailto:polacek@redhat.com">polacek@redhat.com</a>.</p>
<p>Last update:
-Fri Nov 5 11:06:02 AM EDT 2021
+Tue Nov 23 12:36:13 PM EST 2021
</p>
</body>