c - 枚举 DirectSound 设备描述导致不必要的问号

Question

我正在枚举所有 DirectSound 输出设备并存储它们的描述以供以后在我的进程运行时使用。当我使用 OutputDebugStringW 检查结果时，我得到了正确的设备名称，但附加了不必要的问号。即这个...

BOOL CALLBACK AudioPrivate::DSEnumProc(LPGUID lpGUID,
                                       LPCWSTR lpszDesc,
                                       LPCWSTR lpszDevName,
                                       LPVOID lpData) {
    pDeviceInfo[nDevices].lpGUID = lpGUID;
    pDeviceInfo[nDevices].lpszDesc = new WCHAR[wcslen(lpszDesc)];
    pDeviceInfo[nDevices].lpszDevName = new WCHAR[wcslen(lpszDevName)];

    ZeroMemory(pDeviceInfo[nDevices].lpszDesc, sizeof(WCHAR) * wcslen(lpszDesc));
    ZeroMemory(pDeviceInfo[nDevices].lpszDevName, sizeof(WCHAR) * wcslen(lpszDevName));

    memcpy(pDeviceInfo[nDevices].lpszDesc, lpszDesc, sizeof(WCHAR) * wcslen(lpszDesc));
    memcpy(pDeviceInfo[nDevices].lpszDevName, lpszDevName, sizeof(WCHAR) * wcslen(lpszDevName));

    OutputDebugStringW(L"\n");
    OutputDebugStringW(pDeviceInfo[nDevices].lpszDesc);
    OutputDebugStringW(L"\n");
    OutputDebugStringW(pDeviceInfo[nDevices].lpszDevName);
    OutputDebugStringW(L"\n");

    //vs
    OutputDebugString(L"\n");
    OutputDebugStringW(lpszDesc);
    OutputDebugStringW(L"\n");
    OutputDebugStringW(lpszDevName);
    OutputDebugStringW(L"\n");

    nDevices++;

    return TRUE;
}

...结果如下:

Primary Sound Driver????????????
????????

Primary Sound Driver



Speakers (Conexant SmartAudio HD)???????????
{0.0.0.00000000}.{0698bbc7-d0ba-4445-a5a7-a63b625c4298}?????????

Speakers (Conexant SmartAudio HD)
{0.0.0.00000000}.{0698bbc7-d0ba-4445-a5a7-a63b625c4298}

我正在清空我自己的字符串的内存，所以只有当 Enum Proc 提供的字符串中有这些问号时才会发生这种情况，但正如所证明的那样，它们没有。为什么会这样？

Answer 1

您必须为字符串终止符(也包括 NULL 字符)保留空间，此行将只为字符串分配空间，没有终止符:

pDeviceInfo[nDevices].lpszDesc = new WCHAR[wcslen(lpszDesc)];

这是因为 wcslen() 返回不带终止符的字符串长度(参见 reference )。只需更改为(当然对于所有字符串):

pDeviceInfo[nDevices].lpszDesc = new WCHAR[wcslen(lpszDesc) + 1];
pDeviceInfo[nDevices].lpszDevName = new WCHAR[wcslen(lpszDevName) + 1];

和:

ZeroMemory(pDeviceInfo[nDevices].lpszDesc, sizeof(WCHAR) * (wcslen(lpszDesc) + 1));
ZeroMemory(pDeviceInfo[nDevices].lpszDevName, sizeof(WCHAR) * (wcslen(lpszDevName) + 1));