使用std :: runtime_error而不是CException

Question

When I throw a CException in the main thread, it is neatly caught by the framework and a nice MessageBox shows the error text. When I throw an std::runtime_error the application just crashes. The problem is I don't see the text of the exception, and I have to spend time to figure out it's actually something I've 'thrown' instead of simply an access violation.

So I'm wondering if there's a way to make std::exception be caught and its text displayed in a similar way as CException.

I'd like to be able to throw an std::runtime_error from any message handler without crashing my program, without wrapping every message handler in try...catch. This is already possible for CException, because there is a try...catch somewhere in the code for the event pump (I think it's CWinApp::Run - but I'm not sure).

[Edit] I found the function that catches CExceptions, but I'm not sure if it's possible to override it. I've posted the code below. The TRY...CATCH_ALL...END_CATCH_ALL statements are catching the CExceptions.

/////////////////////////////////////////////////////////////////////////////
// Official way to send message to a CWnd

LRESULT AFXAPI AfxCallWndProc(CWnd* pWnd, HWND hWnd, UINT nMsg,
    WPARAM wParam = 0, LPARAM lParam = 0)
{
    _AFX_THREAD_STATE* pThreadState = _afxThreadState.GetData();
    MSG oldState = pThreadState->m_lastSentMsg;   // save for nesting
    pThreadState->m_lastSentMsg.hwnd = hWnd;
    pThreadState->m_lastSentMsg.message = nMsg;
    pThreadState->m_lastSentMsg.wParam = wParam;
    pThreadState->m_lastSentMsg.lParam = lParam;

#ifdef _DEBUG
    _AfxTraceMsg(_T("WndProc"), &pThreadState->m_lastSentMsg);
#endif

    // Catch exceptions thrown outside the scope of a callback
    // in debug builds and warn the user.
    LRESULT lResult;
    TRY
    {
#ifndef _AFX_NO_OCC_SUPPORT
        // special case for WM_DESTROY
        if ((nMsg == WM_DESTROY) && (pWnd->m_pCtrlCont != NULL))
            pWnd->m_pCtrlCont->OnUIActivate(NULL);              
#endif

        // special case for WM_INITDIALOG
        CRect rectOld;
        DWORD dwStyle = 0;
        if (nMsg == WM_INITDIALOG)
            _AfxPreInitDialog(pWnd, &rectOld, &dwStyle);

        // delegate to object's WindowProc
        lResult = pWnd->WindowProc(nMsg, wParam, lParam);

        // more special case for WM_INITDIALOG
        if (nMsg == WM_INITDIALOG)
            _AfxPostInitDialog(pWnd, rectOld, dwStyle);
    }
    CATCH_ALL(e)
    {
        lResult = AfxProcessWndProcException(e, &pThreadState->m_lastSentMsg);
        TRACE(traceAppMsg, 0, "Warning: Uncaught exception in WindowProc (returning %ld).\n",
            lResult);
        DELETE_EXCEPTION(e);
    }
    END_CATCH_ALL

    pThreadState->m_lastSentMsg = oldState;
    return lResult;
}

Answer 1

So I'm wondering if there's a way to make std::exception be caught and its text displayed in a similar way as CException.

Yes- by catching it, and displaying it's text via MessageBox.

int main() {
    try {
        //....
    }
    catch(const std::exception& except) {
        MessageBox(NULL, except.what(), "OMGWTF FATAL ERROR", MB_OK);
    }
}

Answer 2

There is, but you have to do it yourself. :-)

int main()
{
    try
    {
        SomeFunction();
    }
    catch (const std::exception & ex)
    {
        ::MessageBox(0, ex.what(), 0, 0);
    }
}

Answer 3

Somewhere within MFC's implementation of the main message loop it has a try/catch setup that gives the behavior you see when CException types are thrown.

You could wrap your own code in various try/catch statements to catch the exceptions, as already stated by others.

It would also be possible to wrap MFC's message loop with a kind of "top level" handler to catch anything not caught otherwise. To do this, override CWinApp::Run in your derived application class, implement your desired try/catch, and call the base CWinApp::Run from within your try block.

int CMyApp::Run()
{
    try
    {
        return CWinApp::Run();
    }
    catch(const std::exception& ex)
    {
        MessageBox(NULL, ex.what(), "Error", MB_OK | MB_ICONERROR);
        return 1;  // or some appropriate code
    }
}

Answer 4

如果您有可以合理地继续执行的异常，则还可以替代CWinApp :: Run（）或在CWinApp :: Run（）之外重写CWinApp :: PumpMessage（）。