XCreateWindow fails on CentOS 5.6 with error: BadValue

Question

I'm using the following code to create a fake window for some integration tests:

class CXWindowsClipboardTests
{
protected:
    virtual void
    SetUp()
    {
        m_display = XOpenDisplay(NULL);
        int screen = DefaultScreen(m_display);
        Window root = XRootWindow(m_display, screen);

        XSetWindowAttributes attr;
        attr.do_not_propagate_mask = 0;
        attr.override_redirect = True;
        attr.cursor = Cursor();

        m_window = XCreateWindow(
            m_display, root, 0, 0, 1, 1, 0, 0,
            InputOnly, CopyFromParent,
            CWDontPropagate | CWEventMask |
            CWOverrideRedirect | CWCursor,
            &attr);
    }

    virtual void
    TearDown()
    {
        XDestroyWindow(m_display, m_window);
        XCloseDisplay(m_display);
    }
};

The above is a modified version of original code to take up less space (see full source code).

The above code fails intermittently on CentOS 5.6 with the following error:

X Error of failed request:  BadValue
  (integer parameter out of range for operation)
  Major opcode of failed request:  1 (X_CreateWindow)
  Value in failed request:  0x844b530
  Serial number of failed request:  7
  Current serial number in output stream:  8

So, two questions really:

• What could cause XCreateWindow to fail on CentOS intermittently in this way?
• And, I'm fairly new to X development, so I have no idea what the various error values mean (e.g. Value in failed request) or how to use them. Could someone briefly explain these for me?

Answer 1

You're using the CWEventMask but not initializing attr.event_mask. This could be your problem. (since the structure is created on stack, it'll contain random data in that field.)