[PATCH v2 15/24] Avoid another inferior_ptid reference in gdb/remote.c

Pedro Alves
2019-10-17T22:50:45Z

From: Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>

The multi-target patch makes inferior_ptid point to null_ptid before
calling into target_wait, which catches bad uses of inferior_ptid,
since the current selected thread in gdb shouldn't have much relation
to the thread that reports an event.

One such bad use is found in remote_target::remote_parse_stop_reply,
where we handle the 'W' or 'X' packets (process exit), and the remote
target does not support the multi-process extensions, i.e., it does
not report the PID of the process that exited.

With the multi-target patch, that would result in a failed assertion,
trying to find the inferior for process pid 0.

gdb/ChangeLog:
yyyy-mm-dd Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Pedro Alves <palves@redhat.com>

* remote.c (remote_target::remote_parse_stop_reply) <W/X packets>:
If no process is specified, return null_ptid instead of
inferior_ptid.
(remote_target::wait_as): Handle TARGET_WAITKIND_EXITED /
TARGET_WAITKIND_SIGNALLED with no pid.

gdb/testsuite/ChangeLog:
yyyy-mm-dd Tankut Baris Aktemur <tankut.baris.aktemur@intel.com>
Pedro Alves <palves@redhat.com>

* gdb.server/connect-without-multi-process.exp: Also test
continuing to end.
---
gdb/remote.c | 18 +++++++++++++-----
.../gdb.server/connect-without-multi-process.exp | 7 ++++++-
2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/gdb/remote.c b/gdb/remote.c
index 553f09a6e0..e33dedae26 100644
--- a/gdb/remote.c
+++ b/gdb/remote.c
@@ -7446,7 +7446,6 @@ Packet: '%s'\n"),
case 'W': /* Target exited. */
case 'X':
{
- int pid;
ULONGEST value;

/* GDB used to accept only 2 hex chars here. Stubs should
@@ -7470,8 +7469,9 @@ Packet: '%s'\n"),
event->ws.value.sig = GDB_SIGNAL_UNKNOWN;
}

- /* If no process is specified, assume inferior_ptid. */
- pid = inferior_ptid.pid ();
+ /* If no process is specified, return null_ptid, and let the
+ caller figure out the right process to use. */
+ int pid = 0;
if (*p == '\0')
;
else if (*p == ';')
@@ -7847,8 +7847,16 @@ remote_target::wait_as (ptid_t ptid, target_waitstatus *status, int options)
event_ptid = first_remote_resumed_thread ();
}
else
- /* A process exit. Invalidate our notion of current thread. */
- record_currthread (rs, minus_one_ptid);
+ {
+ /* A process exit. Invalidate our notion of current thread. */
+ record_currthread (rs, minus_one_ptid);
+ /* It's possible that the packet did not include a pid. */
+ if (event_ptid == null_ptid)
+ event_ptid = first_remote_resumed_thread ();
+ /* EVENT_PTID could still be NULL_PTID. Double-check. */
+ if (event_ptid == null_ptid)
+ event_ptid = magic_null_ptid;
+ }

return event_ptid;
}
diff --git a/gdb/testsuite/gdb.server/connect-without-multi-process.exp b/gdb/testsuite/gdb.server/connect-without-multi-process.exp
index fba20a6a0b..6ba35bf508 100644
--- a/gdb/testsuite/gdb.server/connect-without-multi-process.exp
+++ b/gdb/testsuite/gdb.server/connect-without-multi-process.exp
@@ -14,7 +14,7 @@
# along with this program. If not, see <http://www.gnu.org/licenses/>. */

# Check that we can connect to GDBserver with the multiprocess
-# extensions disabled, and run to main.
+# extensions disabled, run to main, and finish the process.

load_lib gdbserver-support.exp

@@ -52,6 +52,11 @@ proc do_test {multiprocess} {
"target $gdbserver_protocol"

gdb_test "continue" "main .*" "continue to main"
+
+ # The W/X packets do not include the PID of the exiting process
+ # without the multi-process extensions. Check that we handle
+ # process exit correctly in that case.
+ gdb_continue_to_end
}

foreach multiprocess { "off" "auto" } {
--
2.14.5