Always quit GDB after running a dejagnu test case

That a third take on solving an issue with targets not being reset properly.
It relies on GDB server (nSIM in this case) to implement k-packet to reset
target. Typically gdb-comm.exp board used for nSIM-GDB testing reuses GDB
instance, however that causes troubles in some cases:

1. Unfortunate combination of PC+BLINK registers causes a failed assertion
in generic GDB code. Target should be reset before GDB disconnects from it.

2. GDB sometimes fails to properly load debug symbols from new file, at
least when this file has asme name as before, but different contents. This
problem is sporadic, so I'm not sure what are exact conditions for
reprodcution, but having same time stamaps doesn't cause issue. To avoid
this GDB should be restarted completely between tests. While restarting it
will also send k-packet to target, which will rest it.

Signed-off-by: Anton Kolesov <[email protected]>

Author: anthony-kolesov

dejagnu/nsim-extra.exp

@@ -111,4 +111,24 @@ proc arc-nsim_reboot { connhost args } {
     return 1
 }
 
+# There are problems with GDB loading new application with `file` command, at
+# least when new file has same filename as the old one. That problem is
+# not-deterministic and I wasn't able to trace down the source, however I see
+# that this happened between 7.5 and 7.6. To avoid troubles - restart GDB
+# completely.  Note that it is known that GDB might misbehave when it connects
+# to target which has already set PC and BLINK register, so to avoid possible
+# issues gdbserver should be reset before disconnection. Here we rely on server
+# to implement k-packet, sent by GDB on "quit" command. Another option is to
+# reset registers manually or restart GDB-server completely. The latter is
+# highly undesirable, because it creates huge overhead in typical Dejagnu test
+# cases, which are very-very small, but there is lots of them.
+
+# Standard gdb_comm_leave will simply disconnect from target and will reuse
+# same GDB for next test.
+proc gdb_comm_leave { } {
+    global gdb_prompt
+    verbose "ARC specific gdb_comm_leave"
+    quit_gdb
+}
+
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