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<HTML><!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><!-- Created on September, 12 2004 by texi2html 1.64 --><!-- Written by: Lionel Cons <Lionel.Cons@cern.ch> (original author) Karl Berry <karl@freefriends.org> Olaf Bachmann <obachman@mathematik.uni-kl.de> and many others.Maintained by: Olaf Bachmann <obachman@mathematik.uni-kl.de>Send bugs and suggestions to <texi2html@mathematik.uni-kl.de> --><HEAD><TITLE>Autoconf, Automake, and Libtool: Libtool C++ support</TITLE><META NAME="description" CONTENT="Autoconf, Automake, and Libtool: Libtool C++ support"><META NAME="keywords" CONTENT="Autoconf, Automake, and Libtool: Libtool C++ support"><META NAME="resource-type" CONTENT="document"><META NAME="distribution" CONTENT="global"><META NAME="Generator" CONTENT="texi2html 1.64"><script language="Javascript"><!-- // Check the browser version. function checkVersion() { if (navigator.appVersion.charAt(0)>=3) return true; if (navigator.appVersion.charAt(0)>=4) return true; else return false; 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It is very easy to naively build a shared libraryfrom C++ source using <CODE>libtool</CODE>:</P><P><TABLE width=100%><tr><td> </td><td class=example bgcolor=#6688aa><br><pre>$ libtool -mode=link g++ -o libfoo.la -rpath /usr/local/lib foo.c++</pre></td></tr></table></P><P>This works admirably for trivial examples, but with real code, there areseveral things that can go wrong:</P><P><UL><LI>On many architectures, for a variety of reasons, <CODE>libtool</CODE> needsto perform object linking using <CODE>ld</CODE>. Unfortunately, the C++compiler often links in standard libraries at this stage, and using<CODE>ld</CODE> causes them to be dropped.<P>This can be worked around (at the expense of portability) by explicitlyadding these missing libraries to the link line in your <TT>`Makefile'</TT>.You could even write an Autoconf macro to probe the host machine todiscover likely candidates.</P><P><LI>The C++ compiler likes to instantiate static constructors in the libraryobjects, which C++ programmers often rely on. Linking with <CODE>ld</CODE>will cause this to fail.<P>The only reliable way to work around this currently is to not write C++that relies on static constructors in libraries. You might be luckyenough to be able to link with <CODE>LD=$CXX</CODE> in your environment withsome projects, but it would be prone to stop working as your projectdevelops.</P><P><LI>Libtool's inter-library dependency analysis can fail when it can't findthe special runtime library dependencies added to a shared library bythe C++ compiler at link time.<P>The best way around this problem is to explicitly add these dependenciesto <CODE>libtool</CODE>'s link line:</P><P><TABLE width=100%><tr><td> </td><td class=example bgcolor=#6688aa><br><pre>$ libtool -mode=link g++ -o libfoo.la -rpath /usr/local/lib foo.cxx \-lstdc++ -lg++</pre></td></tr></table></UL><P>Now that C++ compilers on Unix are beginning to see widespreadacceptance and are converging on the ISO standard, it is becomingunacceptable for Libtool to impose such limits. There is work afoot toprovide generalized multi-language and multi-compiler support intoLibtool----currently slated to arrive in Libtool 1.5. Much of the workfor supporting C++ is already finished at the time of writing, pendingbeta testing and packaging<A NAME="DOCF36" HREF="autobook_fot.html#FOOT36">(36)</A>.</P><P><A NAME="Further Reading"></A></TR></TABLE><BR> <FONT SIZE="-1">This document was generatedby <I>Gary V. Vaughan</I> on <I>September, 12 2004</I>using <A HREF="http://www.mathematik.uni-kl.de/~obachman/Texi2html"><I>texi2html</I></A></BODY></HTML>⌨️ 快捷键说明
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