How should I use FormatMessage() properly in C++?

Question

Without:

• MFC
• ATL

How can I use FormatMessage() to get the error text for a HRESULT?

 HRES         


        

Answer 1

The code below is code is the C++ equivalent I've written out in contrast to Microsoft's ErrorExit() but slightly altered to avoid all macros and use unicode. The idea here is to avoid unnecessary casts and mallocs. I couldn't escape all of the C casts but this is the best I could muster. Pertaining to FormatMessageW(), which requires a pointer to be allocated by the format function and the Error Id from the GetLastError(). The pointer after static_cast can be used like a normal wchar_t pointer.

#include 
#include 

void __declspec(noreturn) error_exit(const std::wstring FunctionName)
{
    // Retrieve the system error message for the last-error code
    const DWORD ERROR_ID = GetLastError();
    void* MsgBuffer = nullptr;
    LCID lcid;
    GetLocaleInfoEx(L"en-US", LOCALE_RETURN_NUMBER | LOCALE_ILANGUAGE, (wchar_t*)&lcid, sizeof(lcid));

    //get error message and attach it to Msgbuffer
    FormatMessageW(
        FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
        NULL, ERROR_ID, lcid, (wchar_t*)&MsgBuffer, 0, NULL);
    //concatonate string to DisplayBuffer
    const std::wstring DisplayBuffer = FunctionName + L" failed with error " + std::to_wstring(ERROR_ID) + L": " + static_cast(MsgBuffer);

    // Display the error message and exit the process
    MessageBoxExW(NULL, DisplayBuffer.c_str(), L"Error", MB_ICONERROR | MB_OK, static_cast(lcid));

    ExitProcess(ERROR_ID);
}