Debugging

[topa]

LookingGlass:

It aims to be the Firebug of GNOME Shell

exec: ALT + F2 + lg

Though it seems to not log errors on Ghome-Shell 3.6+. Instead errors will be logged here:

~/.cache/gdm/session.log or ~/.xsession_errors

But I can't confirm this behavior, cause I haven't found any of those files on my Fedora 19 machine. Either my installed extensions haven't thrown any errors yet (can't believe it) or Fedora does log errors somewhere else. @matthaias can you please check if you can locate those files?

There is still another possibility to see errors. If you start LookingGlass you can switch to the Extension-pane. There you're able to see errors for each installed extension. But this is awful, because if LookingGlass is open you'll be unable to use your desktop.

[topa]

I found Debugging GNOME Shell - What the fuck is this for a painful way?

[matthaias]

I checked it on ubuntu. I found the /.xsession_errors file, but not the /.cache/gdm/session.log

[topa]

#! gnome-shell --replace

If you execute in terminal gnome-shell --replace a terminal opens where you'll be able to see all thrown errors and log-statements. But I have no idea how to return from this replace-mode.

I created those files manually, however they don't log anything - even in replace-mode.

I've tested this by throwing an error in the "hello world"-extension. @matthaias can you please test if you can find error-logs those files?

[topa]

gdb

I'll setup an VM for development and playing around with gdb (#10 (comment)). Also I'll document here which packages I'll install. Maybe we add and maintain some cookbooks in this repo to quickly build a dev-vm with vagrant.

[topa]

I've made the following steps:

1. installed UbuntuGnome 13.04 64bit on Vbox
2. installed Vbox Guest Additions
3. installed openssh-server (used this howto: http://linuxg.net/how-to-enable-ssh-on-ubuntu-13-04/)
4. run software-updater and installed about 200MB of updates
5. added this script to home folder, named it like suggested xenv.sh

gnome_session=$(pgrep -u $USER gnome-session)
eval export $(sed 's/\o000/\n/g;' < /proc/$gnome_session/environ | grep DISPLAY)
eval export $(sed 's/\o000/\n/g;' < /proc/$gnome_session/environ | grep XAUTHORITY)
eval export $(sed 's/\o000/\n/g;' < /proc/$gnome_session/environ | grep DBUS_SESSION_BUS_ADDRESS)

1. created with gnome-shell-extension-tool a demo "Hello World"-extension and edited it to throw an error throw new Error("outch!").
   (enabled extension through gnome-tweak-tool)
2. opened a terminal and connected via ssh to the vm
3. ran sudo sh ./xenv.sh
4. ran ./src/gnome-shell --replace -g which is not possible because there is no folder ./src.
   9.1 Supposed that gnome-shell --replace -g was meant, but this error occured

gnome-shell: Unknown option -g

9.2 ran gnome-shell --replace and sudo gnome-shell --replace, but

Window manager error: Unable to open X display

1. ran gdb attach $(pidof gnome-shell), but

Could not attach to process. If your uid matches the uid of the target
process, check the setting of /proc/sys/kernel/yama/ptrace_scope, or try
again as the root user. For more details, see /etc/sysctl.d/10-ptrace.conf
ptrace: Operation not permitted.

10.1 ran sudo gdb attach $(pidof gnome-shell), but gnome-shell immediately freezes until I had quit gdb.

10.2 ran gdb /usr/bin/gnome-shell and then in gdb run --replace, but again

Window manager error: Unable to open X display

I have no idea what I'm doing wrong ...