On Wed, Apr 28, 2010 at 02:50:50PM +0800, Ma, Qingyu (GE Healthcare) wrote: > Hello, > > During my developing work, I meet a problem about XOpenDisplay. Could > you please give me some consult?
please don't cross-post. taking xorg-devel off the CC list. > I'm developing a system, which uses fvwm as WM. Two fvwm are executed to > implement two separated screens. My process is displayed on one > screen(DISPLAY). It calls XOpenDisplay(NULL) to get one Display > connection to be used as display image, and another Display to be used > as toggle keyboard led (whenever keyboard led state is changed, a new > Display is opened and closed). The function is OK. But when I was doing > monkey and cycle test, there is a very very little possibility that my > process may crash. I looked through my code, and found a bug which was > that I didn't check the return value of XOpenDisplay, and use it > directly . I have checked that a NULL Display will cause process crash > in following code. It's just my analysis and guess, I'm not sure whether > it does be the root cause. And, by now, the cycle and monkey cannot > re-occur the issue. > > So, I want to get some information from you to help to reach the root > cause. What will cause XOpenDisplay return NULL? How can I simulate the > case?(When my process is executed, I'm sure the XWindow and fvwm have > been booted up.) XOpenDisplay on an invalid display will return NULL. so you can either specify an invalid display in the code directly or through your DISPLAY environment variable. DISPLAY=:10 your-program-name should fail, unless you really have an X server on display 10 which is rather unlikely. Cheers, Peter _______________________________________________ [email protected]: X.Org support Archives: http://lists.freedesktop.org/archives/xorg Info: http://lists.freedesktop.org/mailman/listinfo/xorg
