docs: debugging.md: add a sample gdbinit file

This gdbinit contains recommended settings
commonly useful for debugging scylla core dumps.

Signed-off-by: Benny Halevy <bhalevy@scylladb.com>

docs/guides/debugging.md

@@ -149,6 +149,9 @@ places. You can always load it by hand if GDB refuses or fails to load it:
 
     (gdb) source /path/to/your/.gdbinit
 
+Scylla provides the following [gdbinit](../../gdbinit) file helpful for debugging scylla
+at the root of the source tree.
+
 #### TUI
 
 GDB has a terminal based GUI called

gdbinit

@@ -0,0 +1,19 @@
+# Recommended .gdbinit for debugging scylla
+# See docs/guides/debugging.md for more information
+handle SIG34 pass noprint
+handle SIGUSR1 pass noprint
+set print pretty
+set python print-stack full
+set auto-load safe-path /opt/scylladb/libreloc
+add-auto-load-safe-path /lib64
+add-auto-load-safe-path /usr/lib64
+set debug libthread-db 1
+
+# Register pretty-printer helpers for printing common
+# std-c++ stl containers.
+python
+import glob
+sys.path.insert(0, glob.glob('/usr/share/gcc-*/python')[0])
+from libstdcxx.v6.printers import register_libstdcxx_printers
+register_libstdcxx_printers (None)
+end