[Bug-gdb] GDB and X11 server grabs

[Jesse Marlin]

Pierre Sarrazin writes:
 > A GDB breakpoint can totally freeze an X11 display when debugging
 > a GUI application, if the app makes a "server grab."
 > 
 > For example, if the application has a pull-down menu and I put
 > a breakpoint in the menu's callback, then the following happens:
 > 
 > - the menu is opened and an X11 server grab happens (in order to
 >   catch all mouse events even if they are outside the menu's window);
 > 
 > - the callback is called and GDB stops on it due to the breakpoint;
 > 
 > - GDB expects commands from the user, but the user cannot type
 >   anything anywhere in the display because of the server grab;
 >   of course, the menu cannot be closed because the app is stopped.
 > 
 > One way to get out of this is to login through the network and
 > kill GDB.  Usually, I access the machine through a VNC remote
 > display.  In addition, I telnet into the machine and run GDB in it,
 > sending the display to the VNC/X11 server.  When the breakpoint is
 > reached, I can still control GDB through the telnet session.
 > 
 > Is there a better way?  I would imagine that GDB could automatically
 > try to end an X11 server grab every time it displays its prompt.

Try changing to window manager focus to Click to Focus.  This usually
happens for focus set to Focus follows Mouse.

Whenever I need to debug something like this I usually manually set a
breakpoint to a point after the popup is popped back.

 > 
 > -- 
 > Pierre Sarrazin <address@hidden>
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