I went through all cp/ commits in GCC 14 and documented a few interesting
user-visible changes, modulo Modules.
W3 validated. Pushed.
commit d65752191baaa137eb6d604b802e7b9170a39752
Author: Marek Polacek <pola...@redhat.com>
Date: Wed Apr 10 17:21:09 2024 -0400
gcc-14/changes: Document more C++ changes
diff --git a/htdocs/gcc-14/changes.html b/htdocs/gcc-14/changes.html
index 4a063346..5c2439ab 100644
--- a/htdocs/gcc-14/changes.html
+++ b/htdocs/gcc-14/changes.html
@@ -273,6 +273,9 @@ a work-in-progress.</p>
</li>
<li>Several C++23 features have been implemented:
<ul>
+ <li><a href="https://wg21.link/P0847R7";>P0847R7</a>, Deducing this
+ (<a href="https://gcc.gnu.org/PR102609";>PR102609</a>)
+ </li>
<li><a href="https://wg21.link/P2280R4";>P2280R4</a>, Using unknown
references in constant expressions
(<a href="https://gcc.gnu.org/PR106650";>PR106650</a>)
@@ -289,12 +292,26 @@ a work-in-progress.</p>
</li>
<li>Several C++ Defect Reports have been resolved, e.g.:
<ul>
+ <li><a href="https://wg21.link/cwg532";>DR 532</a>,
+ Member/nonmember operator template partial ordering</li>
<li><a href="https://wg21.link/cwg976";>DR 976</a>,
Deduction for <code>const T&</code> conversion operators</li>
+ <li><a href="https://wg21.link/cwg2262";>DR 2262</a>,
+ Attributes for <em>asm-definition</em></li>
+ <li><a href="https://wg21.link/cwg2359";>DR 2359</a>,
+ Unintended copy initialization with designated initializers</li>
+ <li><a href="https://wg21.link/cwg2386";>DR 2386</a>,
+ <code>tuple_size</code> requirements for structured binding</li>
<li><a href="https://wg21.link/cwg2406";>DR 2406</a>,
<code>[[fallthrough]]</code> attribute and iteration statements</li>
<li><a href="https://wg21.link/cwg2543";>DR 2543</a>,
<code>constinit</code> and optimized dynamic initialization</li>
+ <li><a href="https://wg21.link/cwg2586";>DR 2586</a>,
+ Explicit object parameter for assignment and comparison</li>
+ <li><a href="https://wg21.link/cwg2735";>DR 2735</a>,
+ List-initialization and conversions in overload resolution</li>
+ <li><a href="https://wg21.link/cwg2799";>DR 2799</a>,
+ Inheriting default constructors</li>
</ul>
</li>
<li>
@@ -304,6 +321,85 @@ a work-in-progress.</p>
the template is instantiated ("<code>required from here</code>"),
rather than just print filename and line/column numbers.
</li>
+ <li>New built-in <code>__type_pack_element</code> to speed up traits
+ such as <code>std::tuple_element</code>
+ (<a href="https://gcc.gnu.org/PR100157";>PR100157</a>)</li>
+ <li><code>goto</code> can cross the initialization of a trivially initialized
+ object with a non-trivial destructor
+ (<a href="https://cplusplus.github.io/CWG/issues/2256.html";>DR
2256</a>)</li>
+ <li><code>-Wdangling-reference</code> false positives have been reduced. The
+ warning does not warn about <code>std::span</code>-like classes; there is
+ also a new attribute <code>gnu::no_dangling</code> to suppress the
+ warning. See
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Dialect-Options.html#index-Wdangling-reference";>the
manual</a>
+ for more info.</li>
+ <li><em>noexcept(expr)</em> is now mangled as per the Itanium ABI</li>
+ <li>the named return value optimization can now be performed even for
+ variables declared in an inner block of a function, see the
+ <a
href="https://gcc.gnu.org/git/?p=gcc.git;a=blob;f=gcc/testsuite/g%2B%2B.dg/opt/nrv23.C;h=9e1253cd830a84ad4de5ff3076a07c543afe344f;hb=7e0b65b239c3a0d68ce94896b236b03de666ffd6";>
+ test</a></li>
+ <li>New <code>-Wnrvo</code> warning, to warn if the named return value
+ optimization is not performed although it is allowed by
+ [class.copy.elision]. See
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wnrvo";>the
manual</a>
+ for more info.</li>
+ <li>The backing array for <code>std::initializer_list</code> has been made
+ static, allowing combining multiple equivalent initializer-lists
+ (<a
href="https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=4d935f52b0d5c00fcc154461b87415ebd8791a94";>git</a>)
+ </li>
+ <li>New <code>-Welaborated-enum-base</code> warning, to warn if an additional
+ enum-base is used in an elaborated-type-specifier</li>
+ <li>Better <code>#include</code> hints for missing headers
+ (<a href="https://gcc.gnu.org/PR110164";>PR110164</a>)</li>
+ <li>The arguments of a variable template-id are coerced earlier than
+ before, so various problems are detected earlier
+ (<a href="https://gcc.gnu.org/PR89442";>PR89442</a>)</li>
+ <li><code>-Wmissing-field-initializers</code> is no longer emitted for
+ empty classes
+ (<a href="https://gcc.gnu.org/PR110064";>PR110064</a>)</li>
+ <li>The constexpr code now tracks lifetimes in constant evaluation; this
+ change helps to detect bugs such as accessing a variable whose
+ lifetime has ended
+ (<a href="https://gcc.gnu.org/PR70331";>PR70331</a>,
+ <a href="https://gcc.gnu.org/PR96630";>PR96630</a>,
+ <a href="https://gcc.gnu.org/PR98675";>PR98675</a>)
+ </li>
+ <li>Array destruction can now be devirtualized</li>
+ <li>In-class member variable template partial specializations are now
+ accepted (<a href="https://gcc.gnu.org/PR71954";>PR71954</a>)</li>
+ <li>Improved diagnostic for explicit conversion functions: when a conversion
+ doesn't work out only because the conversion function necessary to do the
+ conversion couldn't be used because it was marked explicit, explain that
+ to the user
+ (<a
href="https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=85ad41a494e31311f8a6b2dbe930a128c5e85840";>git</a>)</li>
+ <li>Corrected mangling of <code>static</code>/<code>thread_local</code>
+ structured bindings at function/block scope
+ (<a href="https://gcc.gnu.org/PR111069";>PR111069</a>)</li>
+ <li>[basic.scope.block]/2 violations are detected even in
<em>compound-stmt</em> of
+ <em>function-try-block</em> and for block-scope external variables
+ (<a href="https://gcc.gnu.org/PR52953";>PR52953</a>)</li>
+ <li>Improved "not a constant expression" diagnostic when taking the address
+ of a non-static constexpr variable
+ (<a href="https://gcc.gnu.org/PR91483";>PR91483</a>)</li>
+ <li>Non-dependent simple assignments are checked even in templates
+ (<a href="https://gcc.gnu.org/PR18474";>PR18474</a>)</li>
+ <li>Attributes <code>hot</code> and <code>cold</code> can be applied to
+ classes as well. See
+ <a
href="https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Attributes.html#index-cold-type-attribute";>the
manual</a>
+ for more info.</li>
+ <li>Function template constraints, as well as CTAD placeholders, are
+ now mangled</li>
+ <li>Various <code>decltype</code> fixes:
+ <a href="https://gcc.gnu.org/PR79620";>PR79620</a>,
+ <a href="https://gcc.gnu.org/PR79378";>PR79378</a>,
+ <a href="https://gcc.gnu.org/PR83167";>PR83167</a>,
+ <a href="https://gcc.gnu.org/PR96917";>PR96917</a></li>
+ <li>New option <code>-fdiagnostics-all-candidates</code> to note all
+ candidates during overload resolution failure</li>
+ <li><code>-Walloc-size</code> and <code>-Wcalloc-transposed-args</code>
+ warnings are enabled for C++ as well</li>
+ <li>The DR 2237 code no longer gives an error, it emits
+ a <code>-Wtemplate-id-cdtor</code> warning instead</li>
</ul>
<h4 id="libstdcxx">Runtime Library (libstdc++)</h4>
