In case you haven't, take a look at How to Roslaunch Nodes in Valgrind or GDB.
Especially the run your node in gdb in a new [..] window variants of the prefixes, such as:
launch-prefix="xterm -e gdb --args"
: run your node in a gdb in a separate xterm window, manually type run to start it launch-prefix="gdb -ex run --args"
: run your node in gdb in the same xterm as your launch without having to type run to start it
I don't know how should I see xterm window when I launch the nodes using gdb.
If you already tried the two launch-prefix
es I list above, but still can't find the window, make sure it is not being spawned behind the terminal you use to roslaunch
everything in. That has happened to me some times and it can make for a confusing 5 minutes.
There's not enough detail here for us to help. Please edit your question to add the commands that you're running, and the output that you do see. If you're using a launch file please include that launch file too.