为什么QueryInterface()返回E_INVALIDARG？

Question

我在编写一个项目时遇到了一个QueryInterface()返回E_INVALIDARG的bug，我不知道哪个参数是无效的，因为这两个参数都够简单的，我是不是忽略了一些简单的东西？

失败的部分来自微软自己，特别是文档，如果我做错了什么，告诉我

HRESULT CreateSecondaryBuffer(LPDIRECTSOUND8 lpDirectSound, LPDIRECTSOUNDBUFFER8* ppDsb8, LPCWSTR lpName) {
    WAVEFORMATEX wfx;
    DSBUFFERDESC dsbdesc;
    LPDIRECTSOUNDBUFFER pDsb = NULL;
    HRESULT hr = 0;

    void* lpRes;
    HRSRC hResInfo;
    HGLOBAL hRes;

    LPVOID lpvWrite;
    DWORD  dwLength;

    waveFile myWave;
    memset(&myWave, 0, sizeof(waveFile));
    // Find the WAVE resource. 

    hResInfo = FindResource(wc.hInstance, lpName, L"WAVE");
    if (hResInfo == NULL)
        return FALSE;

    // Load the WAVE resource. 

    hRes = LoadResource(wc.hInstance, hResInfo);
    if (hRes == NULL)
        return FALSE;

    // Lock the WAVE resource and play it. 

    lpRes = LockResource(hRes);
    char* wavMem = static_cast<char*>(lpRes);
    memcpy(&myWave, wavMem, 36);
    wavMem += 36;
    

    while (myWave.Subchunk2ID[0] != 'd' && myWave.Subchunk2ID[1] != 'a' && myWave.Subchunk2ID[2] != 't' && myWave.Subchunk2ID[3] != 'a') {
        memcpy(&myWave.Subchunk2ID, wavMem, 8);
        if (myWave.Subchunk2ID[0] != 'd' && myWave.Subchunk2ID[1] != 'a' && myWave.Subchunk2ID[2] != 't' && myWave.Subchunk2ID[3] != 'a') {
            wavMem += myWave.Subchunk2Size;
            wavMem += 8;
        }
    }
    wavMem += 8;

    char* soundData = new char[myWave.Subchunk2Size];
    memcpy(soundData, wavMem, myWave.Subchunk2Size);
    FreeResource(hRes);

    // Set up WAV format structure. 

    memset(&wfx, 0, sizeof(WAVEFORMATEX));
    wfx.wFormatTag = WAVE_FORMAT_PCM;
    wfx.nChannels = myWave.NumChannels;
    wfx.nSamplesPerSec = myWave.SampleRate;
    wfx.nBlockAlign = myWave.BlockAlign;
    wfx.nAvgBytesPerSec = wfx.nSamplesPerSec * wfx.nBlockAlign;
    wfx.wBitsPerSample = myWave.BitsPerSample;

    // Set up DSBUFFERDESC structure. 

    memset(&dsbdesc, 0, sizeof(DSBUFFERDESC));
    dsbdesc.dwSize = sizeof(DSBUFFERDESC);
    dsbdesc.dwFlags =
         DSBCAPS_CTRLVOLUME | DSBCAPS_GLOBALFOCUS;
    dsbdesc.dwBufferBytes = myWave.Subchunk2Size;
    dsbdesc.lpwfxFormat = &wfx;

    hr = lpDirectSound->CreateSoundBuffer(&dsbdesc, &pDsb, NULL);
    if (SUCCEEDED(hr))
    {
        if (DS_OK == pDsb->Lock(
            0,          // Offset at which to start lock.
            0,          // Size of lock; ignored because of flag.
            &lpvWrite,  // Gets address of first part of lock.
            &dwLength,  // Gets size of first part of lock.
            NULL,       // Address of wraparound not needed. 
            NULL,       // Size of wraparound not needed.
            DSBLOCK_ENTIREBUFFER))  // Flag.
        {
            memcpy(lpvWrite, soundData, dwLength);
            pDsb->Unlock(
                lpvWrite,   // Address of lock start.
                dwLength,   // Size of lock.
                NULL,       // No wraparound portion.
                0);         // No wraparound size.
        }
        hr = pDsb->QueryInterface(IID_IDirectSoundBuffer8, (LPVOID*)ppDsb8);
        pDsb->Release();
    }

    delete[] soundData;
    return hr;
}

Answer 1

QueryInterface()只有两个参数可供E_INVALIDARG抱怨，而在您的CreateSecondaryBuffer()函数中，这些参数在我看来还不错。第一个参数正在传递一个硬编码的IID，所以问题必须与第二个参数有关，该参数期望被传递一个指向(在本例中) IDirectSoundBuffer8*变量的指针，QueryInterface()可以将DirectSoundBuffer8对象的内存地址写入其中。因此，最有可能的情况是，您的ppDsb8函数的CreateSecondaryBuffer()参数不会像您所期望的那样传递到IDirectSoundBuffer8*变量的有效指针。

UPDATE:在看到添加的注释后，确实传递了指向CreateSecondaryBuffer()的ppDsb8参数的无效指针。调用方的pMainSecondaryBuffer指针被不正确地声明，并且在传递给CreateSecondaryBuffer()时未初始化，因此您将一个错误的指针传递到QueryInterface()，从而导致E_INVALIDARG错误。

用这个代替：

LPDIRECTSOUND8 lpDevice = ...; // <-- make sure it points to a valid device object...
LPDIRECTSOUNDBUFFER8 pMainSecondaryBuffer;
CreateSecondaryBuffer(lpDevice, &pMainSecondaryBuffer, L"mainSong");