$ for file in *.cpp *.h *.bat ; do echo "--------------------- $file -----------------" ; cat "$file" ; echo "" ; done
--------------------- A.cpp -----------------
#include "stuff.h"

printFunc_t print=nullptr;

extern "C" void loadA( printFunc_t func ) {
        print = func;
    (*print)("A: loading libB\n");

        auto B = dlopen("./libB.dll", RTLD_LAZY);
    if ( CheckDlError() != 0 )
                return;

    (*print)("A: getting libB::loadB()\n");
    auto loadB = reinterpret_cast< loaderFunc_t >( dlsym( B, "loadB" ) );

    if ( CheckDlError() != 0 )
                return;

        (*print)("A: calling libB::loadB()\n");
    (*loadB)( func );

        (*print)("A: closing libB\n");
        dlclose(B);
        int a = 0;
}

--------------------- B.cpp -----------------
#include "stuff.h"

extern "C" void loadB( printFunc_t func ) {
    (*func)("B: I am loaded\n");
}

--------------------- stub.cpp -----------------
#include "stuff.h"

void Print( const char * msg ) {
        printf("%s", msg);
        fflush(stdout);
}

int main() {
    Print("stub: loading libA\n");
        auto A = dlopen("./libA.dll", RTLD_LAZY);
    if ( CheckDlError() != 0 )
                return -1;

    Print("stub: getting libA::loadA()\n");
    auto loadA = reinterpret_cast< loaderFunc_t >( dlsym( A, "loadA" ) );
    if ( CheckDlError() != 0 )
                return -1;

        Print("stub: calling libA::loadA()\n");
        (*loadA)( &Print );

        Print("stub: closing libA\n");
        dlclose(A);
}

--------------------- stuff.h -----------------
#include <cstdio>
#include <cassert>

#ifdef _WIN32
    #include "windows.h"
    #define dlopen( file, flag ) LoadLibrary( file )
    #define dlsym( module, resource ) reinterpret_cast<void*>( GetProcAddress( module, resource ) )
    #define dlclose( module ) FreeLibrary( module )
#elif defined(__linux)
    #include <dlfcn.h>
#endif

bool CheckDlError( void );
inline bool CheckDlError( void ) {
    #ifdef _WIN32
        return GetLastError() == 0;
    #elif defined(__linux)
        const char *error = dlerror();
        if ( error )  {
            printf("Error linking library: %s\n", error);
            return true;
        }
    #endif
    return false;
}

typedef void ( *printFunc_t )( const char* msg );
typedef void ( *loaderFunc_t )( printFunc_t );
typedef void ( *voidFunc_t )( void );

--------------------- build.bat -----------------
rm A.dll B.dll stub.exe 2>>/dev/null

g++ B.cpp -shared -g -ggdb -Wl,--export-all-symbols -o libB.dll
g++ A.cpp -shared -g -ggdb -Wl,--export-all-symbols -o libA.dll
g++ stub.cpp -g -ggdb -Wl,--export-all-symbols -o stub