Now I remove +s bit from /usr/bin/X, /usr/bin/xinit, /usr/bin/startx, /usr/bin/Xorg and tried to run Valgrind with it. Honestly I have no idea about debugging. I just know that valgrind and strace can be somehow use for it. Hope this helps!
output of valgrind -v startx 1> valgrind_v_startx.txt 2>&1 ** Attachment added: "valgrind_v_startx.txt" https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1754296/+attachment/5072779/+files/valgrind_v_startx.txt -- You received this bug notification because you are a member of Ubuntu-X, which is subscribed to xorg in Ubuntu. https://bugs.launchpad.net/bugs/1754296 Title: [bionic] startx / xinit crashes with Composite Disabled in xorg.conf To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/xorg/+bug/1754296/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~ubuntu-x-swat Post to : [email protected] Unsubscribe : https://launchpad.net/~ubuntu-x-swat More help : https://help.launchpad.net/ListHelp

