Listing 12: ex4lnx.cpp, C++ file on Linux.

// ex4lnx.cpp  —  Test file for passing a function pointer to an 
// F77 function in a dll
#include <iostream>
#include <dlfcn.h>
float foo(float &x)
{
    return x * 2.0f;
}
int main()
{
    void *hDll = dlopen("./ex4.so", RTLD_NOW);
    typedef float (*pMyFunc)(float&);
    typedef float (* LPFNDLLFUNC)(pMyFunc, float&);
    LPFNDLLFUNC lpFunc = NULL;
    lpFunc = (LPFNDLLFUNC)dlsym(hDll, "myeval_");
    float x,y;
    pMyFunc pfunc = (pMyFunc) foo;
    x = 1.2f;
    y = lpFunc(pfunc, x);
    std::cout << "foo( " << x << " ) " << " = "
                           << y << std::endl;
    dlclose(hDll);
    return 0;
}