libstdc++: Use LTLIBICONV when linking libstdc++.so [PR93602]

This fixes missing libiconv symbols when libstdc++ is built on a system
that has libiconv installed. If the libiconv headers are found then
libstdc++ depends on libiconv_open etc instead of libc's iconv_open. But
without this fix libstdc++ is not linked to the libiconv library that
provides the definitions of those symbols.

As discussed in PR 93602 this changed means that libstdc++.so.6 might
have an rpath pointing to the location of the libiconv.so library. If
that is not desired, then GCC must be configured to link to a static
libiconv.a instead, using either --with-libiconv-type=static or an
in-tree build of libiconv.

libstdc++-v3/ChangeLog:

	PR libstdc++/93602
	* doc/xml/manual/prerequisites.xml: Document libiconv
	workarounds.
	* doc/html/manual/setup.html: Regenerate.
	* src/Makefile.am (CXXLINK): Add $(LTLIBICONV).
	* src/Makefile.in: Regenerate.
This commit is contained in:
Jonathan Wakely 2022-04-13 14:09:33 +01:00
parent 4d4eaa77a7
commit c644b7df11
4 changed files with 89 additions and 2 deletions

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@ -42,6 +42,39 @@
</p><p>
Finally, a few system-specific requirements:
</p><div class="variablelist"><dl class="variablelist"><dt><span class="term">linux</span></dt><dd><p>
The 'gnu' locale model makes use of <code class="function">iconv</code>
for character set conversions. The relevant functions are provided
by Glibc and so are always available, however they can also be
provided by the separate GNU libiconv library. If GNU libiconv is
found when GCC is built (e.g., because its headers are installed
in <code class="filename">/usr/local/include</code>)
then the <code class="filename">libstdc++.so.6</code> library will have a
run-time dependency on <code class="filename">libiconv.so.2</code>.
If you do not want that run-time dependency then you should do
one of the following:
</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
Uninstall the libiconv headers before building GCC.
Glibc already provides <code class="function">iconv</code> so you should
not need libiconv anyway.
</p></li><li class="listitem"><p>
<a class="link" href="../">
Download</a> the libiconv sources and extract them into the
top level of the GCC source tree, e.g.,
</p><pre class="programlisting">
wget https://ftp.gnu.org/pub/gnu/libiconv/libiconv-1.16.tar.gz
tar xf libiconv-1.16.tar.gz
ln -s libiconv-1.16 libiconv
</pre><p>
This will build libiconv as part of building GCC and link to
it statically, so there is no <code class="filename">libiconv.so.2</code>
dependency.
</p></li><li class="listitem"><p>
Configure GCC with <code class="option">--with-libiconv-type=static</code>.
This requires the static <code class="filename">libiconv.a</code> library,
which is not installed by default. You might need to reinstall
libiconv using the <code class="option">--enable-static</code> configure
option to get the static library.
</p></li></ul></div><p>
If GCC 3.1.0 or later on is being used on GNU/Linux, an attempt
will be made to use "C" library functionality necessary for
C++ named locale support. For GCC 4.6.0 and later, this

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@ -48,6 +48,56 @@
<varlistentry>
<term>linux</term>
<listitem>
<para>
The 'gnu' locale model makes use of <function>iconv</function>
for character set conversions. The relevant functions are provided
by Glibc and so are always available, however they can also be
provided by the separate GNU libiconv library. If GNU libiconv is
found when GCC is built (e.g., because its headers are installed
in <filename class="directory">/usr/local/include</filename>)
then the <filename>libstdc++.so.6</filename> library will have a
run-time dependency on <filename>libiconv.so.2</filename>.
If you do not want that run-time dependency then you should do
one of the following:
</para>
<itemizedlist>
<listitem>
<para>
Uninstall the libiconv headers before building GCC.
Glibc already provides <function>iconv</function> so you should
not need libiconv anyway.
</para>
</listitem>
<listitem>
<para>
<link linkend="https://www.gnu.org/software/libiconv/#downloading">
Download</link> the libiconv sources and extract them into the
top level of the GCC source tree, e.g.,
</para>
<programlisting>
wget https://ftp.gnu.org/pub/gnu/libiconv/libiconv-1.16.tar.gz
tar xf libiconv-1.16.tar.gz
ln -s libiconv-1.16 libiconv
</programlisting>
<para>
This will build libiconv as part of building GCC and link to
it statically, so there is no <filename>libiconv.so.2</filename>
dependency.
</para>
</listitem>
<listitem>
<para>
Configure GCC with <option>--with-libiconv-type=static</option>.
This requires the static <filename>libiconv.a</filename> library,
which is not installed by default. You might need to reinstall
libiconv using the <option>--enable-static</option> configure
option to get the static library.
</para>
</listitem>
</itemizedlist>
</listitem>
<listitem>
<para>
If GCC 3.1.0 or later on is being used on GNU/Linux, an attempt

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@ -278,7 +278,9 @@ CXXLINK = \
$(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \
--mode=link $(CXX) \
$(VTV_CXXLINKFLAGS) \
$(OPT_LDFLAGS) $(SECTION_LDFLAGS) $(AM_CXXFLAGS) $(LTLDFLAGS) -o $@
$(OPT_LDFLAGS) $(SECTION_LDFLAGS) $(AM_CXXFLAGS) \
$(LTLDFLAGS) $(LTLIBICONV) \
-o $@
# Symbol versioning for shared libraries.
if ENABLE_SYMVERS

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@ -643,7 +643,9 @@ CXXLINK = \
$(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) \
--mode=link $(CXX) \
$(VTV_CXXLINKFLAGS) \
$(OPT_LDFLAGS) $(SECTION_LDFLAGS) $(AM_CXXFLAGS) $(LTLDFLAGS) -o $@
$(OPT_LDFLAGS) $(SECTION_LDFLAGS) $(AM_CXXFLAGS) \
$(LTLDFLAGS) $(LTLIBICONV) \
-o $@
@ENABLE_SYMVERS_TRUE@CLEANFILES = libstdc++-symbols.ver $(version_dep)
@ENABLE_SYMVERS_DARWIN_TRUE@@ENABLE_SYMVERS_TRUE@version_arg = -Wl,-exported_symbols_list,libstdc++-symbols.explist