gcc-wwwdocs branch master updated. 768ecbe7af00a219cfdff9fba96874a0fe9c94bb

[Jonathan Wakely <redi@sourceware.org>]

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commit 768ecbe7af00a219cfdff9fba96874a0fe9c94bb
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Jan 14 10:41:43 2021 +0000

    Document addition of <barrier> C++ header in C++11

diff --git a/htdocs/gcc-11/changes.html b/htdocs/gcc-11/changes.html
index e044d710..3527428f 100644
--- a/htdocs/gcc-11/changes.html
+++ b/htdocs/gcc-11/changes.html
@@ -307,7 +307,8 @@ a work-in-progress.</p>
       <li><code>std::bit_cast</code></li>
       <li><code>std::source_location</code></li>
       <li>Atomic wait and notify operations.</li>
-      <li><code>&lt;latch&gt;</code> and <code>&lt;semaphore&gt;</code></li>
+      <li><code>&lt;barrier&gt;</code>, <code>&lt;latch&gt;</code>,
+        and <code>&lt;semaphore&gt;</code></li>
       <li><code>&lt;syncstream&gt;</code></li>
       <li>Efficient access to <code>basic_stringbuf</code>'s buffer.</li>
     </ul>

commit b1448ab2ec847fd9a8283881f620d3ace0aea8ed
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Jan 14 10:40:47 2021 +0000

    Add "porting to" notes for libstdc++ in GCC 11

diff --git a/htdocs/gcc-11/porting_to.html b/htdocs/gcc-11/porting_to.html
index 4187dd8e..83227c74 100644
--- a/htdocs/gcc-11/porting_to.html
+++ b/htdocs/gcc-11/porting_to.html
@@ -141,6 +141,35 @@ change the code to not include the <code>&lt;tr1/functional&gt;</code> header,
 so that only <code>std::bind</code> is declared.
 </p>
 
+<h3 id="enable-threads">Enable multithreading to use std::thread</h3>
+<p>
+Programs must be linked to libpthread in order for <code>std::thread</code>
+to create new threads of execution.
+It is not sufficient to use <code>dlopen</code> to dynamically load
+<code>libpthread.so</code> at run-time.
+</p>
+
+<h3 id="strict-ansi">Do not undefine <code>__STRICT_ANSI__</code></h3>
+<p>
+The <code>__STRICT_ANSI__</code> macro is defined by the compiler to
+inform the C and C++ standard library headers when a strict language dialect
+is being used, e.g. <code>-std=c++17</code> or <code>-std=c11</code> rather
+than <code>-std=gnu++17</code> or <code>-std=gnu11</code>.
+</p>
+<p>
+If you undefine the <code>__STRICT_ANSI__</code> macro then you create an
+inconsistent state where the compiler is using a strict dialect but the
+standard library headers think that GNU extensions are enabled.
+The libstdc++ headers in GCC 11 cannot be used in this state and are likely
+to produce compilation errors.
+</p>
+<p>
+If you don't want the macro to be defined, don't use a <code>-std</code>
+option that causes it to be defined.
+Simply use a <code>-std=gnu++<em>NN</em></code> option instead of
+<code>-std=c++<em>NN</em></code>.
+</p>
+
 <!--
 <h2 id="fortran">Fortran language issues</h2>
 -->

-----------------------------------------------------------------------

Summary of changes:
 htdocs/gcc-11/changes.html    |  3 ++-
 htdocs/gcc-11/porting_to.html | 29 +++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)


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