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149
LDP/howto/docbook/C++-dlopen.xml
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@ -1,7 +1,6 @@
<?xml version="1.0" encoding="ISO-8859-1"?>
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
"http://docbook.org/xml/4.2/docbookx.dtd" [
]>
"http://docbook.org/xml/4.2/docbookx.dtd">
<article>
<articleinfo>
@ -16,15 +15,17 @@
</affiliation>
</author>
<pubdate>2002-06-30</pubdate>
<releaseinfo>$Id$</releaseinfo>
<pubdate>2003-08-12</pubdate>
<revhistory>
<!-- I only keep the last 5 revision updates here; I keep the
document in CVS, if you're interested in more exact change logs
you can email me. -->
<revision>
<revnumber>1.03</revnumber>
<date>2003-08-12</date>
<authorinitials>AI</authorinitials>
<revremark>Added reference to the GLib Dynamic Module
Loader. Thanks to G. V. Sriraam for the pointer.</revremark>
</revision>
<revision>
<revnumber>1.02</revnumber>
@ -73,16 +74,14 @@
</revhistory>
<abstract>
<para>
How to dynamically load C++ functions and classes using the
<function>dlopen</function> API.
</para>
<para>How to dynamically load C++ functions and classes using
the <function>dlopen</function> API.</para>
</abstract>
</articleinfo>
<sect1 id="intro">
<section id="intro">
<title>Introduction</title>
<para>
@ -102,7 +101,7 @@
<para>This HOWTO's master location is <ulink
url="http://www.isotton.com/howtos/C++-dlopen-mini-HOWTO/"/>.</para>
<sect2 id="copyright">
<section id="copyright">
<title>Copyright and License</title>
<para>
@ -114,9 +113,9 @@
Free Software Foundation; with no Invariant Sections, with no
Front-Cover Texts, and with no Back-Cover Texts.
</para>
</sect2>
</section>
<sect2 id="disclaimer">
<section id="disclaimer">
<title>Disclaimer</title>
<para>
@ -135,9 +134,9 @@
any trademark or service mark. Naming of particular products
or brands should not be seen as endorsements.
</para>
</sect2>
</section>
<sect2 id="credits">
<section id="credits">
<title>Credits / Contributors</title>
<para>
@ -161,9 +160,9 @@
</itemizedlist>
</sect2>
</section>
<sect2 id="feedback">
<section id="feedback">
<title>Feedback</title>
<para>
@ -171,9 +170,9 @@
your additions, comments and criticisms to the following email
address: <email>aaron@isotton.com</email>.
</para>
</sect2>
</section>
<sect2>
<section>
<title>Terms Used in this Document</title>
<variablelist>
@ -196,10 +195,10 @@
</varlistentry>
</variablelist>
</sect2>
</section>
<!-- Translations - ->
<sect2 id="translations">
<section id="translations">
<title>Translations</title>
<para>
@ -221,11 +220,11 @@
</para>
</listitem>
</itemizedlist>
</sect2>
</section>
-->
</sect1>
</section>
<sect1 id="theproblem">
<section id="theproblem">
<title>The Problem</title>
<para>At some time you might have to load a library (and use its
@ -248,7 +247,7 @@
even if you're not interested in it because it will help you
understanding why problems occur and how to solve them.</para>
<sect2 id="mangling">
<section id="mangling">
<title>Name Mangling</title>
<para>In every C++ program (or library, or object file), all
@ -287,9 +286,9 @@
probably work with your compiler only, and might already be
broken with the next version.</para>
</sect2>
</section>
<sect2>
<section>
<title>Classes</title>
<para>Another problem with the <function>dlopen</function> API
@ -299,14 +298,14 @@
program. Obviously, to use that class you need to create an
instance of it, but that cannot be easily done.</para>
</sect2>
</section>
</sect1>
</section>
<sect1 id="thesolution">
<section id="thesolution">
<title>The Solution</title>
<sect2 id="externC">
<section id="externC">
<title><literal>extern "C"</literal></title>
<para>C++ has a special keyword to declare a function with C
@ -326,9 +325,9 @@
code. Such a function is a full-featured C++ function which
can use C++ features and take any type of argument.</para>
</sect2>
</section>
<sect2 id="loadingfunctions">
<section id="loadingfunctions">
<title>Loading Functions</title>
<para>In C++ functions are loaded just like in C, with
@ -387,7 +386,6 @@ extern "C" void hello() {
std::cout << "hello" << '\n';
}
]]></programlisting>
</example>
<para>The function <function>hello</function> is defined in
@ -411,8 +409,10 @@ extern "C" void hello() {
<programlisting>extern "C" int foo;
extern "C" void bar();
</programlisting>
</informalexample>
and
<programlisting>extern "C" {
<informalexample>
<programlisting>extern "C" {
extern int foo;
extern void bar();
}</programlisting>
@ -427,11 +427,13 @@ extern "C" void bar();
<informalexample>
<programlisting>extern "C" int foo;</programlisting>
</informalexample>
and
<programlisting>extern "C" {
<informalexample>
<programlisting>extern "C" {
int foo;
}</programlisting>
</informalexample>
</informalexample>
are <emphasis>not</emphasis> the same thing.</para>
@ -446,9 +448,9 @@ extern "C" void bar();
</warning>
</sect2>
</section>
<sect2 id="loadingclasses">
<section id="loadingclasses">
<title>Loading Classes</title>
<para>Loading classes is a bit more difficult because we need
@ -618,10 +620,10 @@ extern "C" void destroy(polygon* p) {
</listitem>
</itemizedlist>
</sect2>
</sect1>
</section>
</section>
<sect1 id="faq">
<section id="faq">
<title>Frequently Asked Questions</title>
<qandaset>
<qandaentry>
@ -635,28 +637,48 @@ extern "C" void destroy(polygon* p) {
<filename>dlfcn.h</filename> header on Windows,and there is
no <function>dlopen</function> API. There is a similar API
around the <function>LoadLibrary</function> function, and
most of what is written here applies to it, too. Refer to
the Win32 Platform SDK documentation or have a look at
<ulink url="http://msdn.microsoft.com">MSDN</ulink>.</para>
most of what is written here applies to it, too.
Alternatively, you can use libltdl (included in libtool) to
<quote>emulate</quote> <function>dlopen</function> on a
variety of platforms.</para>
<para>You should also read section 4, <quote>Dynamically
Loaded (DL) Libraries</quote>, of the <ulink
url="http://www.dwheeler.com/program-library">Program Library
HOWTO</ulink> for more techniques to load libraries and
create classes independently of your platform.</para>
</answer>
</qandaentry>
<qandaentry>
<question>
<para>Is there some kind of
<function>dlopen</function>-compatible wrapper for the
Windows <function>LoadLibrary</function> API?</para>
<question>
<para>Is there some kind of <function>dlopen</function>-compatible
wrapper for the Windows <function>LoadLibrary</function>
API?</para>
</question>
<answer>
<para>I don't know, and honestly I don't care. If you know
of something, feel free mailing me and I'll eventually put
it here.</para>
<answer>
<para>I don't know of any, and I don't think there'll ever be one
supporting all of <function>dlopen</function>'s options.</para>
<para>There are alternatives though: libtltdl (a part of libtool),
which wraps a variety of different dynamic loading APIs, among
others <function>dlopen</function> and
<function>LoadLibrary</function>. Another one is the <ulink
url="http://developer.gnome.org/doc/API/glib/glib-dynamic-loading-of-modules.html">Dynamic
Module Loading functionality of GLib</ulink>. You can use one
of these to ensure better possible cross-platform compatibility.
I've never used any of them, so I can't tell you how stable they
are and whether they really work.</para>
</answer>
</qandaentry>
</qandaset>
</sect1>
</section>
<sect1 id="seealso">
<section id="seealso">
<title>See Also</title>
<itemizedlist>
@ -703,7 +725,7 @@ extern "C" void destroy(polygon* p) {
</itemizedlist>
</sect1>
</section>
<bibliography>
@ -716,8 +738,8 @@ extern "C" void destroy(polygon* p) {
<bibliomixed>
<abbrev>STR2000</abbrev>
<author><surname>Stroustrup</surname>,
<firstname>Bjarne</firstname>.</author>
<author><surname>Stroustrup</surname>
<firstname>Bjarne</firstname></author>
<title>The C++ Programming Language</title>, <edition>Special
Edition</edition>.
ISBN <isbn>0-201-70073-5</isbn>.
@ -728,6 +750,3 @@ extern "C" void destroy(polygon* p) {
</article>
<!-- LocalWords: dlopen
-->

2
LDP/howto/docbook/HOWTO-INDEX/howtoChap.sgml
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@ -639,7 +639,7 @@ This HOWTO has been removed for review. </Para>
<ULINK URL="../C++-dlopen/index.html">C++-dlopen</ULink>,
<CiteTitle>C++ dlopen mini HOWTO</CiteTitle>
</Para><Para>
<CiteTitle>Updated: December 2002</CiteTitle>.
<CiteTitle>Updated: August 2003</CiteTitle>.
How to dynamically load C++ functions and classes using
the dlopen API. </Para>
</ListItem>

2
LDP/howto/docbook/HOWTO-INDEX/programmSect.sgml
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@ -242,7 +242,7 @@ and dynamically loaded libraries. </Para>
<ULINK URL="../C++-dlopen/index.html">C++-dlopen</ULink>,
<CiteTitle>C++ dlopen mini HOWTO</CiteTitle>
</Para><Para>
<CiteTitle>Updated: December 2002</CiteTitle>.
<CiteTitle>Updated: August 2003</CiteTitle>.
How to dynamically load C++ functions and classes using
the dlopen API. </Para>
</ListItem>