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libstdc++: Document missing features for old std:string ABI [PR116777]

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There are several features that are not supported when using the old
std::string ABI. It's possible that PR 81967 will get fixed, but the
missing C++20 features almost certainly won't be. Document this in the
manual.

libstdc++-v3/ChangeLog:

	PR libstdc++/116777
	* doc/xml/manual/using.xml: Document features that are not
	supported for the gcc4-compatible ABI.
	* doc/html/manual/using_dual_abi.html: Regenerate.
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Jonathan Wakely 2024-09-20 17:35:48 +01:00 committed by Jonathan Wakely
parent 9227a64495
commit 8230922230
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18
libstdc++-v3/doc/html/manual/using_dual_abi.html
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@ -22,7 +22,7 @@
of the macro is <code class="literal">1</code> which causes the new ABI to be active,
so to use the old ABI you must explicitly define the macro to
<code class="literal">0</code> before including any library headers.
(Be aware that some GNU/Linux distributions configure GCC 5 differently so
(Be aware that some GNU/Linux distributions configured GCC 5 differently so
that the default value of the macro is <code class="literal">0</code> and users must
define it to <code class="literal">1</code> to enable the new ABI.)
</p><p> Although the changes were made for C++11 conformance, the choice of ABI
@ -72,6 +72,22 @@
Handlers for <code class="classname">std::exception</code> will always catch
iostreams exceptions, because the old and new type both inherit from
<code class="classname">std::exception</code>.
</p><p>
Some features are not supported when using the old ABI, including:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">
Using <code class="classname">std::string::const_iterator</code> for
positional arguments to member functions such as
<code class="function">std::string::erase</code>.
</li><li class="listitem">
Allocator propagation in <code class="classname">std::string</code>.
</li><li class="listitem">
Using <code class="classname">std::string</code> at compile-time in
<code class="code">constexpr</code> functions.
</li><li class="listitem">
Class <code class="classname">std::chrono::time_zone</code> and all related APIs.
</li><li class="listitem">
The <code class="filename">&lt;syncstream&gt;</code> header.
</li></ul></div><p>
</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a id="manual.intro.using.abi.trouble"></a>Troubleshooting</h3></div></div></div><p> If you get linker errors about undefined references to symbols
that involve types in the <code class="code">std::__cxx11</code> namespace or the tag
<code class="code">[abi:cxx11]</code> then it probably indicates that you are trying to

26
libstdc++-v3/doc/xml/manual/using.xml
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@ -1368,7 +1368,7 @@ g++ -Winvalid-pch -I. -include stdc++.h -H -g -O2 hello.cc -o test.exe
of the macro is <literal>1</literal> which causes the new ABI to be active,
so to use the old ABI you must explicitly define the macro to
<literal>0</literal> before including any library headers.
(Be aware that some GNU/Linux distributions configure GCC 5 differently so
(Be aware that some GNU/Linux distributions configured GCC 5 differently so
that the default value of the macro is <literal>0</literal> and users must
define it to <literal>1</literal> to enable the new ABI.)
</para>
@ -1428,6 +1428,30 @@ g++ -Winvalid-pch -I. -include stdc++.h -H -g -O2 hello.cc -o test.exe
<classname>std::exception</classname>.
</para>
<para>
Some features are not supported when using the old ABI, including:
<itemizedlist>
<listitem>
Using <classname>std::string::const_iterator</classname> for
positional arguments to member functions such as
<function>std::string::erase</function>.
</listitem>
<listitem>
Allocator propagation in <classname>std::string</classname>.
</listitem>
<listitem>
Using <classname>std::string</classname> at compile-time in
<code>constexpr</code> functions.
</listitem>
<listitem>
Class <classname>std::chrono::time_zone</classname> and all related APIs.
</listitem>
<listitem>
The <filename class="headerfile">&lt;syncstream&gt;</filename> header.
</listitem>
</itemizedlist>
</para>
<section xml:id="manual.intro.using.abi.trouble" xreflabel="Dual ABI Troubleshooting"><info><title>Troubleshooting</title></info>
<para> If you get linker errors about undefined references to symbols