On Mon, Mar 29, 2010 at 3:24 PM, Coder Bean <[email protected]> wrote:
> > > On Mon, Mar 29, 2010 at 12:18 AM, Manohar Vanga > <[email protected]>wrote: > >> Actually if the header file is simply included (which it was), name >> mangling is not a problem. The function missing was called subscribe(). Here >> are the tests: >> >> $ nm server | grep subscribe >> 0804f090 T _ZN5Server6Module16subscribeEjj >> >> The above is the mangled name within the server binary (the function lies >> in the Server::Module namespace). The "T" indicates that it is in the text >> segment of the binary. >> >> Now, when I compile the module with the header file for the server >> included: >> >> $ nm Modules/testmodule.so | grep subscribe >> U _ZN5Server6Module16subscribeEjj >> >> The "U" here means this symbol is undefined. Note that the compiler >> generated the mangled name correctly as in the server. The issue of name >> mangling only makes a difference when different compilers are used for >> modules and the main loader. Note that even extern "C" is not needed unless >> compiling the two parts with different compilers. The reason for using them >> is to have consistency across all compilers (I don't really care about this >> as modules are part of the source and I will compile them together with the >> main loader using one compiler). >> > > I thought you wanted it to be loadable using dlopen. If you link it this > way, main app will have dependency on the so file and therefore would > require it while running the main app itself. If you want it to be like a > loadable plugin, you would have to follow the approach I mentioned in my > previous mail. Main app should never link with the plugin. Otherwise the > whole concept of "plug-in" is useless, as you won't be able to plug-out. > The main app is not linked or dependent on the plugin in any way. If you see the nm output above, the main app has the function as a part of it. The plugin has an undefined reference. The main app has no undefined references and runs fine without the plugin. The plugin on the other hand has a dependency on the main app (which is normal for the idea of a plugin). It has an undefined reference that gets satisfied only when linked to the main app. The only requirement is that the plugin and main app generate the same names for the functions. This is done automatically if the plugin includes the declaration of the missing function (the server header files). Name mangling doesn't come into the picture at all. Thanks Manohar
