Question

I am trying to print something using C++. However, I am running into a strange bug that has left me clueless, I use the following code:

PRINTDLG pd;
ZeroMemory(&pd, sizeof(pd));
pd.lStructSize = sizeof(pd);
pd.Flags = PD_RETURNDEFAULT;
PrintDlg(&pd);

// Set landscape
DEVMODE* pDevMode = (DEVMODE*)GlobalLock(pd.hDevMode);
pDevMode->dmOrientation = DMORIENT_LANDSCAPE;
pd.hwndOwner = mainWindow;
pd.Flags = PD_RETURNDC | PD_NOSELECTION;
GlobalUnlock(pd.hDevMode);

if (PrintDlg(&pd))
{
    DOCINFO di;

    di.cbSize       = sizeof(DOCINFO);
    di.lpszDocName  = "Test Print";
    di.lpszOutput   = (LPTSTR)NULL;
    di.fwType       = 0;

    //start printing
    StartDoc(pd.hDC, &di);

    int a;
    int b;
    int c;
    int d;
    int e;
    int f;
    // int g; // Uncomment this -> CRASH

    EndDoc(pd.hDC);
    DeleteDC(pd.hDC);
}
else
{
    cout << "Did not print: " <<  CommDlgExtendedError()  << endl;
}

The moment I uncomment ‘int g;’ I get a: “Program received signal SIGSEGV, Segmentation fault.” I use codeblocks and the mingw compiler, both up to date. What could be causing this?

Answer 1

I don’t know if this is a potential problem here – but you should always initialize all members of structures (like you did with the PRINTDLG). In the DOCINFO struct the lpszDataType member is uninitialized. Instead of using ZeroMemory or memset, I prefer something like DOCINFO di = {0};