Question

我试图从FormatMessage方法获取错误消息，但该方法始终返回false并且lpBuffer为null。

我想知道我做错了什么？

Thx

LPTSTR lpBuffer = NULL;
DWORD dwError = GetLastError();
int nResult = 0;
if (dwError >= 12000 && dwError <= 12174)
{
    logger.info("dwError >= 12000 && dwError <= 12174");
    nResult = FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_HMODULE, GetModuleHandle("wininet.dll"), dwError, 0, lpBuffer, 0, NULL);
}
else
{
    logger.info("in else");
    nResult = FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, dwError, MAKELANGID(LANG_ENGLISH, SUBLANG_ENGLISH_US),lpBuffer, 0, NULL);
}

if (nResult)
{
    logger.critical("Cannot start Drools client [" + m_exe + "] because [" + lpBuffer + "]");
    //wcout << (LPWSTR)lpBuffer << endl;
    LocalFree(lpBuffer);
}
else
{
    logger.critical("Cannot start Drools client [" + m_exe + "] because [ Windows error code : " + boost::lexical_cast<string>(dwError) + " ]");
}

Answer 1

你说错了。如果你传递FORMAT_MESSAGE_ALLOCATE_BUFFER，你必须给它存储缓冲区的位置，所以“你必须将指针强制转换为LPTSTR（例如，(LPTSTR)&lpBuffer）。”

I.e：

nResult = FormatMessage(
    FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_HMODULE,
    GetModuleHandle("wininet.dll"), 
    dwError, 
    0, 
    (LPTSTR)&lpBuffer, 
    BUFFER_SIZE, 
    NULL
);

请参阅此处的文档：

http://msdn.microsoft.com/en-us/library/windows/desktop/ms679351(v=vs.85).aspx

Answer 2

您必须将&lpBuffer传递给FormatMessage，而不是lpBuffer。

为什么WinAPI FormatMessage失败，总是返回false

2 个答案: