[gcc r16-8818] libstdc++: Update documentation about default -std option

[Jonathan Wakely]

https://gcc.gnu.org/g:8836c2e79b953f06185e4a040c4e043d6a04263a

commit r16-8818-g8836c2e79b953f06185e4a040c4e043d6a04263a
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Apr 28 17:44:35 2026 +0100

    libstdc++: Update documentation about default -std option
    
    libstdc++-v3/ChangeLog:
    
            * doc/xml/manual/using.xml (Flags): Update description of
            default value for -std option.
            * doc/html/manual/using.html: Regenerate.
    
    (cherry picked from commit eda0f2f0ccc76dfcce0a4d8350611039b0762e05)

Diff:
---
 libstdc++-v3/doc/html/manual/using.html | 5 +++--
 libstdc++-v3/doc/xml/manual/using.xml   | 5 +++--
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/doc/html/manual/using.html b/libstdc++-v3/doc/html/manual/using.html
index 27f503ecaccc..32a1c726cb1e 100644
--- a/libstdc++-v3/doc/html/manual/using.html
+++ b/libstdc++-v3/doc/html/manual/using.html
@@ -11,8 +11,9 @@
       The standard library conforms to the dialect of C++ specified by the
       <code class="option">-std</code> option passed to the compiler.
       By default, <span class="command"><strong>g++</strong></span> is equivalent to
-      <span class="command"><strong>g++ -std=gnu++17</strong></span> since GCC 11, and
-      <span class="command"><strong>g++ -std=gnu++14</strong></span> in GCC 6, 7, 8, 9, and 10, and
+      <span class="command"><strong>g++ -std=gnu++20</strong></span> since GCC 16, and
+      <span class="command"><strong>g++ -std=gnu++17</strong></span> in GCC 11-15, and
+      <span class="command"><strong>g++ -std=gnu++14</strong></span> in GCC 6-10, and
       <span class="command"><strong>g++ -std=gnu++98</strong></span> for older releases.
     </p><div class="table"><a id="table.cmd_options"></a><p class="title"><strong>Table 3.1. C++ Command Options</strong></p><div class="table-contents"><table class="table" summary="C++ Command Options" border="1"><colgroup><col align="left" class="c1" /><col align="left" class="c2" /></colgroup><thead><tr><th align="left">Option Flags</th><th align="left">Description</th></tr></thead><tbody><tr><td align="left"><code class="literal">-std</code>
       </td><td align="left">
diff --git a/libstdc++-v3/doc/xml/manual/using.xml b/libstdc++-v3/doc/xml/manual/using.xml
index 682669d91d4b..e2e75e8fe28c 100644
--- a/libstdc++-v3/doc/xml/manual/using.xml
+++ b/libstdc++-v3/doc/xml/manual/using.xml
@@ -16,8 +16,9 @@
       The standard library conforms to the dialect of C++ specified by the
       <option>-std</option> option passed to the compiler.
       By default, <command>g++</command> is equivalent to
-      <command>g++ -std=gnu++17</command> since GCC 11, and
-      <command>g++ -std=gnu++14</command> in GCC 6, 7, 8, 9, and 10, and
+      <command>g++ -std=gnu++20</command> since GCC 16, and
+      <command>g++ -std=gnu++17</command> in GCC 11-15, and
+      <command>g++ -std=gnu++14</command> in GCC 6-10, and
       <command>g++ -std=gnu++98</command> for older releases.
     </para>