Very Computer

by **root** » Sun, 27 Feb 2000 04:00:00

Hi folks,
I hope I got the right forum for this: im a developer of a new
open-source project (http://threedsia.sourceforge.net) and have a problem
writing plug-ins:
Because we want to use mainly C++ as language I'd like to have C++ plug-ins, or
at least user C++ classes. While we already wrote some plug-ins with C and they
worked fine, I renamed a working plug-in from textonlyFrontEnd.c to *.cpp,
forcing make to use g++ as compiler. Compiles fine, but the resulting library
can't be accessed with dlsym... I already consulted what-ever-doc-I-could-find,
but I've not a suitable solution.
Thnx for any information,
Marc Haisenko

by **Frank V. Castellucc** » Sun, 27 Feb 2000 04:00:00

> Hi folks,
> I hope I got the right forum for this: im a developer of a new
> open-source project (http://threedsia.sourceforge.net) and have a problem
> writing plug-ins:
> Because we want to use mainly C++ as language I'd like to have C++ plug-ins, or
> at least user C++ classes. While we already wrote some plug-ins with C and they
> worked fine, I renamed a working plug-in from textonlyFrontEnd.c to *.cpp,
> forcing make to use g++ as compiler. Compiles fine, but the resulting library
> can't be accessed with dlsym... I already consulted what-ever-doc-I-could-find,
> but I've not a suitable solution.
> Thnx for any information,
> Marc Haisenko

One simple framework to use, without knowing what your requirements are,
can be:

1. Define the abstraction of what you expect your plugins to support.
2. Include in the shared library ( I assume ) a extern "C" factory
method for the plugin implementation.
3. The user specifies the library, you load and test for the common
factory method and viola!

For a general idea of what I mean:

// ----------------------------------------------
// In your engine/framework/application/whatever
// ----------------------------------------------

class AbstractPluginInterface
{
public:

//
// Bunch of pure virtuals, or virtuals with implementation
//

Quote:};

class PluginLoader
{
public:

//...

AbstractPluginInterface *loadPlugin( pluginIdentifier )
{
// load the library identified
// resolve address of "createPlugin"
// invoke the factory method
return (*createFunc)();
}

Quote:};

//----------------------
//In the plugin library:
//----------------------

class PlugInImplementation : public AbstractPluginInterface
{
public:

//
// Implementations of pure virtual or handled interface
//

Quote:};

extern "C"
{
//
// Factory method for plug in
//

AbstractPluginInterface *createPlugin(/* intialization stuff if
needed */)
{
return new PlugInImplementation(...);
}

Quote:}

--
Frank V. Castellucci
http://corelinux.sourceforge.net
OOA/OOD/C++ Standards and Guidelines for Linux

by **Stephe** » Sun, 27 Feb 2000 04:00:00

C++ mangles names. Use extern "C" {} around your function prototypes. Also, use
"nm" to see what symbols are being exported by your lib.

> Hi folks,
> I hope I got the right forum for this: im a developer of a new
> open-source project (http://threedsia.sourceforge.net) and have a problem
> writing plug-ins:
> Because we want to use mainly C++ as language I'd like to have C++ plug-ins, or
> at least user C++ classes. While we already wrote some plug-ins with C and they
> worked fine, I renamed a working plug-in from textonlyFrontEnd.c to *.cpp,
> forcing make to use g++ as compiler. Compiles fine, but the resulting library
> can't be accessed with dlsym... I already consulted what-ever-doc-I-could-find,
> but I've not a suitable solution.
> Thnx for any information,
> Marc Haisenko

by **Jeff Koftino** » Thu, 02 Mar 2000 04:00:00

>Hi folks,
> I hope I got the right forum for this: im a developer of a new
>open-source project (http://threedsia.sourceforge.net) and have a problem
>writing plug-ins:
>Because we want to use mainly C++ as language I'd like to have C++ plug-ins, or
>at least user C++ classes. While we already wrote some plug-ins with C and they
>worked fine, I renamed a working plug-in from textonlyFrontEnd.c to *.cpp,
>forcing make to use g++ as compiler. Compiles fine, but the resulting library
>can't be accessed with dlsym... I already consulted what-ever-doc-I-could-find,
>but I've not a suitable solution.
>Thnx for any information,
> Marc Haisenko

Check out http://www.jdkoftinoff.com/linux1.html
for an example program using c++ & dlsym and object factories for c++
dynamically loaded plugins.

Best Regards

Jeff Koftinoff

Very Computer

Plug-Ins using C++

Plug-Ins using C++

Plug-Ins using C++

Plug-Ins using C++

Plug-Ins using C++