c++ - C++ GetProcAddress 不工作

Question

我有以下代码：

typedef int (WINAPI* fnEngineStart)();


int __stdcall EngineStart()
{
BOOL FreeResult = 0, RunTimeLinkSuccess = 0; //variables for later use
HMODULE LibraryHandle = 0; //Here the handle to API module/dll will be stored.
fnEngineStart fn = 0;

LibraryHandle = AfxLoadLibrary(L"FlowEngine.dll"); //get the handle of our API module
//so it will now be loaded.
if (LibraryHandle != NULL) //if the library loading was successfull..
{
    fn = (fnEngineStart)GetProcAddress(LibraryHandle,
        "fnEngineStart");
    if (RunTimeLinkSuccess = (fn != NULL)) //if operation was successful...
    {
        int ReturnValue = fn(); //call messageboxa function
        //from user32.dll
    }
    else
    {
        MessageBox(0, L"Error", 0, 0);
    }
    FreeResult = FreeLibrary(LibraryHandle);
    //from this process...
    return FreeResult; //routine was successful
}
return EXIT_FAILURE; //else, it failed
}

此代码适用于例如 user32.dll 和 MessageBoxA 但不是我自己的 dll ......

int __declspec(dllexport) __stdcall fnEngineStart()
{
   MessageBox(0, L"Succes!", 0, 0);
   return 0;
}

我如何使它也适用于我自己的 dll？提前致谢。

Answer 1

The issue you are dealing with is Name Mangling. Use extern "C" so the compiler doesn't mangle the name. Example:

extern "C" int __declspec(dllexport) __stdcall fnEngineStart()
{
   MessageBox(0, L"Succes!", 0, 0);
   return 0;
}

Note: __stdcall functions are name-decorated with a leading underscore, followed by an @, and then the number (in bytes) of arguments passed on the stack. This number will always be a multiple of 4, on a 32-bit aligned machine. Source

If your compiler supports it, you can do this in your dll and everything should work the way you have it now.

extern "C" int __declspec(dllexport) __stdcall fnEngineStart()
{
   #pragma comment(linker, "/EXPORT:" __FUNCTION__ "=" __FUNCDNAME__)
   MessageBox(0, L"Succes!", 0, 0);
   return 0;
}