No dialog box for saving bug report,then what can i do?

no dialog box for saving bug report,then what can i do?
sometime it just freeze or crash, even halt with all system.
then, no the default dialog box to save bug report .
and what can i do?
do i run some command or the application for watching bug accident before?

In that case you can launch Debugger (the application)

Set all threads on the left side to state debugged and then choose save debug report from the menu.

You can use this for a freeze, for a crash it should give you the box.
Perhaps the app did not “crash” but closef unexpectendly? In that case you can report it too, devs may have an idea for where to start for that specific app to investigate.

You can try keeping a Terminal visible on your screen and do a tail -f /var/log/syslog there to show a continuously updating syslog. Maybe you see something useful there, even should the whole system freeze up.