Loading a C DLL with LoadLibrary into a C++ Application, Calling Convention Errors

Question

I'm using Visual Studio 2019 with C++.

I'm trying to load a 32-bit DLL written in C code (not by me) into my C++ application. The dll is something called SDL_mixer.dll (an early version of it, SDL_mixer-1.2.12, which is required). I have to load it via LoadLibrary(), because I don't have the import library. I typedefed the functions to import and used GetProcAddress() to access one of them. It accesses it, but then throws an error when the function is called. It gives a guess at the reason for the problem.

It states:

"The value of ESP was not properly saved across a function call. This is usually a result of calling a function declared with one calling convention with a function pointer declared with a different calling convention"

I'm not sure what mistake I'm making. I have on occasion called a C DLL from a C++ application using the LoadLibrary method with success.

Here is the code that I have:

typedef int (WINAPI* Mix_OpenAudioA)(int frequency, Uint16 format, int channel, int chunksize);


int main()
{
    const HINSTANCE hLibrary = LoadLibrary(L"SDL_mixer.dll");

    if (hLibrary == NULL) {
        cout << "Unable to open SDL_mixer.dll\n";
        return 0;
    }

    Mix_OpenAudioA mx_OpnAudio = (Mix_OpenAudioA)GetProcAddress(hLibrary, "Mix_OpenAudio");

     // Calling this function is where the error occurs
    if (mx_OpnAudio(44100, AUDIO_S16, 2, 512) < 0) {
        cout << "Audio Initializer Error\n";
        return 0;
    }
}

Thanks for any help! ...John