While maintaining some of our pretty printers, I've encountered an issue with debug symbols in mongod maybe not being fully loaded. To reproduce the exact issues is a bit complicated, but I'll also give simpler repros.

First, run the attached jstest (python buildscripts/resmoke.py run test.js). This will set up a replica set with the primary on port 20040 with a bunch of sessions in the primary's session catalog. Then, attach gdb to the primary. To do so, you can run lsof -i :20040 and attach to the PID with the NAME column is *:20040 (LISTEN) by running bazel run --config=dbg gdb – -p <pid>.

Now, run mongod-dump-sessions. You'll encounter the first issue: No type named <very long type name I've excluded for readability>. If you jump up to the frame for main and then back down (for example, run frame 8 then frame 0), that error will go away and you'll have a different problem:

(gdb) mongod-dump-sessions
Dumping 20 Session objects from the SessionCatalog
Traceback (most recent call last):
  File "buildscripts/gdb/mongo.py", line 486, in invoke
    lsids_to_print = [str(s["first"]["_id"]) for s in session_kv_pairs]
  File "buildscripts/gdb/mongo.py", line 486, in <listcomp>
    lsids_to_print = [str(s["first"]["_id"]) for s in session_kv_pairs]
gdb.error: There is no member named first.
Error occurred in Python: There is no member named first.

The issue here seems to be that std::pair<mongo::LogicalSessionId const, std::unique_ptr<mongo::SessionCatalog::SessionRuntimeInfo, std::default_delete<mongo::SessionCatalog::SessionRuntimeInfo> > > is an incomplete type according to gdb. Running python pair = get_session_kv_pairs()[0] followed by python print(pair.dereference()) gives <incomplete type>. I think this is also an issues with debug symbols, but to be honest, I'm not really sure.