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

我在Windows7x32下使用RASAPI。以下函数返回错误632（错误无效的大小）：

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)返回错误的大小？怎么可能？
或者我错过了什么？

最佳答案

RASDIALPARAMS这些年来增加了新的字段：

#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，RASDIALPARAMS期望的RasSetEntryDialParams()的大小取决于特定的Windows版本。但应用程序内部RASDIALPARAMS的实际大小取决于编译期间的WINVER定义，如上图所示。
因此，当以Windows7为目标时，WINVER必须设置为至少0x601的值（Windows7是v6.1）。如果使用较低的WINVER值编译，RASDIALPARAMS的大小将太小，Windows 7无法接受。
如果将WINVER设置为比目标Windows版本高的值，则可以在运行时检测操作系统版本并将ras_param.dwSize设置为适当的大小，因为sizeof(RASDIALPARAMS)将大于RasSetEntryDialParams()所期望的大小。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;
}