[committed] libstdc++: Document libstdc++exp.a library for -fcontracts

[Jonathan Wakely]

Pushed to trunk.

-- >8 --

libstdc++-v3/ChangeLog:

	* doc/xml/manual/using.xml: Document libstdc++exp.a library.
	* doc/html/*: Regenerate.

diff --git a/libstdc++-v3/doc/xml/manual/using.xml b/libstdc++-v3/doc/xml/manual/using.xml
index 7f011a6d931..3a507fc1671 100644
--- a/libstdc++-v3/doc/xml/manual/using.xml
+++ b/libstdc++-v3/doc/xml/manual/using.xml
@@ -108,6 +108,14 @@
       </entry>
     </row>
 
+    <row>
+      <entry><literal>-lstdc++exp</literal></entry>
+      <entry>Linking to <filename class="libraryfile">libstdc++exp</filename>
+        is required for use of the C++ Contracts extensions enabled by
+        <literal>-fcontracts</literal>.
+      </entry>
+    </row>
+
     <row>
       <entry><literal>-lstdc++_libbacktrace</literal></entry>
       <entry>Until C++23 support is non-experimental, linking to
@@ -1700,14 +1708,25 @@ A quick read of the relevant part of the GCC
       no shared library for it. To use the library you should include
       <filename class="headerfile"><experimental/filesystem></filename>
       and link with <option>-lstdc++fs</option>. The library implementation
-      is incomplete on non-POSIX platforms, specifically Windows support is
-      rudimentary.
+      is incomplete on non-POSIX platforms, specifically Windows is only
+      partially supported.
     </para>
 
     <para>
-      Due to the experimental nature of the Filesystem library the usual
+      GCC 13 includes an implementation of the C++ Contracts library defined by
+      <link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p1429r3.pdf">P1429R3</link>.
+      Because this is an experimental extension, not part of the C++ standard,
+      it is implemented in a separate library,
+      <filename class="libraryfile">libstdc++exp.a</filename>, and there is
+      no shared library for it. To use the library you should include
+      <filename class="headerfile"><experimental/contract></filename>
+      and link with <option>-lstdc++exp</option>.
+    </para>
+
+    <para>
+      Due to the experimental nature of these libraries the usual
       guarantees about ABI stability and backwards compatibility do not apply
-      to it. There is no guarantee that the components in any
+      to them. There is no guarantee that the components in any
       <filename class="headerfile"><experimental/xxx></filename>
       header will remain compatible between different GCC releases.
     </para>
-- 
2.39.2