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Bug 1806

Summary: Wrong coding practise in src/video/x11/SDL_x11events.c file, may cause an crash
Product: SDL Reporter: Nitz <nitin.j4>
Component: videoAssignee: Sam Lantinga <slouken>
Status: RESOLVED INVALID QA Contact: Sam Lantinga <slouken>
Severity: major    
Priority: P2    
Version: 2.0.0   
Hardware: x86   
OS: Linux   

Description Nitz 2013-04-16 02:46:54 UTC 
in function,
static void
X11_DispatchEvent(_THIS)
{
  // Some Code

  if (videodata && videodata->windowlist) {
        for (i = 0; i < videodata->numwindows; ++i) {
            if ((videodata->windowlist[i] != NULL) &&
                (videodata->windowlist[i]->xwindow == xevent.xany.window)) {
                data = videodata->windowlist[i];
                break;
            }
        }
    }

  // Some Code
}

In the if condition, if (videodata && videodata->windowlist)
videodata is dereferenced while checking the videodata,
if videodata will be NULL then it may cause an crash.

So videodata should be dereferenced after the NULL check.
Comment 1 Sam Lantinga 2013-04-17 04:41:24 UTC 
This does short-circuit evaluation, so if videodata is NULL, the if condition will be false and videodata->windowlist will not be evaluated.

Thanks for checking though!