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linuxgdbxserver

using gdb to debug application started using startx

I have an application with a GUI which I run on the command line, directly in the X server, without using a windows manager: 

sudo startx app args

I'm trying to debug the application and would like to use gdb. How do I start the application in gdb? I've tried this but it doesn't work: 

sudo gdb --args startx app args
Solution

  • I've tried this but it doesn't work

    It doesn't work because startx is a shell script:

    $ file /usr/bin/startx
/usr/bin/startx: POSIX shell script, ASCII text executable

    You almost certainly don't want to debug a shell script with GDB.

    What you probably want is to start the application normally, then attach GDB to it:

    sudo startx app args
sudo gdb -p $(pgrep app)

    Note also that debugging applications from the same display on which the application runs is ill-advised: if you set a breakpoint in a context where the application has grabbed the X server, then all your keystrokes will go to the application, and there would be no way to continue the application.