c++ - How to make application symbols visible to a library? -

i have application loads library dlopen, looks this:

#include <iostream> #include <dlfcn.h>  void foo() {     std::cout << "foo"; }  int main() {     void* libbar = dlopen("./libbar.so", rtld_lazy);     if (!libbar)     {         std::cerr << dlerror() << std::endl;         return 1;     }     void(*bar)() = (void(*)())dlsym(libbar, "bar");     if (!bar)     {         std::cerr << dlerror() << std::endl;         return 1;     }     bar();     dlclose(libbar);  } 

and here libbar:

#include <iostream>  void foo();  extern "c" void bar() {     foo();     std::cout << "bar" << std::endl; } 

output:

./libbar.so: undefined symbol: _z3foov 

expected output:

foobar 

how make foo visible libbar?

i'm using c++ , real problem undefined symbols constructors/member functions, should similar. i'm working on linux gcc 4.7.

you should compile , link main.cc with

 g++ -rdynamic -wall main.cc -o prog -ldl 

the -rdynamic flag important @ link time.

and you'll better declare extern "c" functions want pass dlsym.

see program library howto.