c++ - RAS API。 sizeof(RASDIALPARAMS) 是错误的。错误 632

Question

我在 Windows 7 x32 下使用 RAS API。以下函数返回错误 632 (ERROR_INVALID_SIZE):

int32_t set_username_passwd(wchar_t *entry_title)
{
    RASDIALPARAMS ras_param;
    ZeroMemory(&ras_param, sizeof(RASDIALPARAMS));
    ras_param.dwSize = sizeof(RASDIALPARAMS);
    memcpy(ras_param.szEntryName, entry_title, wcslen(entry_title));
    memcpy(ras_param.szUserName, L"username", wcslen(L"username"));
    memcpy(ras_param.szPassword, L"password", wcslen(L"password"));
    return RasSetEntryDialParams(0, &ras_param, 0);
}

sizeof(RASDIALPARAMS) 返回错误大小？怎么可能？

或者我错过了什么？

Answer 1

RASDIALPARAMS 多年来添加了新字段:

#define RASDIALPARAMSW struct tagRASDIALPARAMSW
RASDIALPARAMSW
{
    DWORD dwSize;
    WCHAR szEntryName[ RAS_MaxEntryName + 1 ];
    WCHAR szPhoneNumber[ RAS_MaxPhoneNumber + 1 ];
    WCHAR szCallbackNumber[ RAS_MaxCallbackNumber + 1 ];
    WCHAR szUserName[ UNLEN + 1 ];
    WCHAR szPassword[ PWLEN + 1 ];
    WCHAR szDomain[ DNLEN + 1 ];
#if (WINVER >= 0x401) // 95/NT4 and later
    DWORD dwSubEntry;
    ULONG_PTR dwCallbackId;
#endif
#if (WINVER >= 0x601) // Windows 7 and later
    DWORD dwIfIndex;
#endif
};

因此，RasSetEntryDialParams() 期望的 RASDIALPARAMS 的大小取决于特定的 Windows 版本。但是 RASDIALPARAMS 在您的应用中的实际大小取决于编译期间定义的 WINVER，如上所示。

因此，当面向 Windows 7 时，WINVER 必须设置为至少为 0x601 的值(Windows 7 是 v6.1)。如果您使用较低的 WINVER 值进行编译，那么 RASDIALPARAMS 的大小将太小，Windows 7 无法接受。

如果将 WINVER 设置为高于目标 Windows 版本的值，则可以在运行时检测操作系统版本并将 ras_param.dwSize 设置为适当的size 因为 sizeof(RASDIALPARAMS) 会比 RasSetEntryDialParams() 预期的要大。例如:

int32_t set_username_passwd(wchar_t *entry_title)
{
    RASDIALPARAMSW ras_param;
    ZeroMemory(&ras_param, sizeof(ras_param));

    OSVERSIONINFO osvi;
    ZeroMemory(&osvi, sizeof(osvi));

    GetVersionEx(&osvi);

    #if (WINVER >= 0x401)
    if ((osvi.dwMajorVersion < 4) ||
       ((osvi.dwMajorVersion == 4) && (osvi.dwMinVersion < 1)) )
    {
        ras_param.dwSize = offsetof(RASDIALPARAMSW, dwSubEntry);
    }
    else
    #endif
    #if (WINVER >= 0x601)
    if ((osvi.dwMajorVersion < 6) ||
       ((osvi.dwMajorVersion == 6) && (osvi.dwMinVersion < 1)) )
    {
        ras_param.dwSize = offsetof(RASDIALPARAMSW, dwIfIndex);
    }
    else
    #endif
    {
        ras_param.dwSize = sizeof(ras_param);
    }

    wcsncpy(ras_param.szEntryName, entry_title, RAS_MaxEntryName);
    wcsncpy(ras_param.szUserName, L"username", UNLEN);
    wcsncpy(ras_param.szPassword, L"password", PWLEN);

    return RasSetEntryDialParamsW(0, &ras_param, 0);
}

或者，您可以跳过操作系统检查，只处理 ERROR_INVALID_SIZE 错误:

int32_t set_username_passwd(wchar_t *entry_title)
{
    RASDIALPARAMSW ras_param;
    ZeroMemory(&ras_param, sizeof(ras_param));

    ras_param.dwSize = sizeof(ras_param);
    wcsncpy(ras_param.szEntryName, entry_title, RAS_MaxEntryName);
    wcsncpy(ras_param.szUserName, L"username", UNLEN);
    wcsncpy(ras_param.szPassword, L"password", PWLEN);

    DWORD dwRet = RasSetEntryDialParamsW(0, &ras_param, 0);
    #if (WINVER >= 0x601)
    if (dwRet == ERROR_INVALID_SIZE)
    {
        ras_param.dwSize = offsetof(RASDIALPARAMSW, dwIfIndex);
        dwRet = RasSetEntryDialParamsW(0, &ras_param, 0);
    }
    #elif (WINVER >= 0x401)
    if (dwRet == ERROR_INVALID_SIZE)
    {
        ras_param.dwSize = offsetof(RASDIALPARAMSW, dwSubEntry);
        dwRet = RasSetEntryDialParamsW(0, &ras_param, 0);
    }
    #endif

    return dwRet;
}