MessageBox Description has only 1 letter

Question

std::string Window::Exception::TranslateErrorCode(HRESULT hr) noexcept
{
    char* pMsgBuf = nullptr;
    DWORD nMsgLen = FormatMessage(
        FORMAT_MESSAGE_ALLOCATE_BUFFER |
        FORMAT_MESSAGE_FROM_SYSTEM |
        FORMAT_MESSAGE_IGNORE_INSERTS,
        nullptr,
        hr,
        MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
        reinterpret_cast<LPWSTR>(&pMsgBuf),
        0,
        nullptr
    );
    if (nMsgLen == 0)
    {
        return "Unidentified error code";
    }
    std::string errorString = pMsgBuf;
    LocalFree(pMsgBuf);
    return errorString;
}

This is the code that returns the description string, however the string on the description is only 1 letter long, i think that the problem is that pMsgBuf that is a LPWSTR, but i don't know how to setup reinterpret_cast with LPSTR, cause if i put LPSTR it gives me an error: "Argument of type 'LPSTR' is incompatible with parameter of type 'LPWSTR'"

Answer 1

First, it's 2024 and using ANSI strings in modern applications is inexcusable. You should set your project to UNICODE and use wide strings.

std::wstring Window::Exception::TranslateErrorCode(HRESULT hr) noexcept
{
    LPWSTR pBuffer = nullptr;

    DWORD Result = FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER |
                      FORMAT_MESSAGE_FROM_SYSTEM |
                      FORMAT_MESSAGE_IGNORE_INSERTS,
                      nullptr,
                      hr,
                      MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                      reinterpret_cast<LPWSTR>(&pBuffer),
                      0,
                      nullptr);
    if (Result == 0) {
        return L"Unidentified error code";
    }

    std::wstring ErrorString = pBuffer;

    LocalFree(pBuffer);

    return ErrorString;
}

Second, you are passing a HRESULT into this code. While you can get an error message text from that you need to be aware that not all HRESULT codes come from FACILITY_WIN32 and that the error message you get back can be completely wrong.