Fix bug in DAP handling of 'pause' requests
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Commit Message
While working on cancellation, I noticed that a DAP 'pause' request
would set the "do not emit the continue" flag. This meant that a
subsequent request that should provoke a 'continue' event would
instead suppress the event.
I then tried writing a more obvious test case for this, involving an
inferior call -- and discovered that gdb.events.cont does not fire for
an inferior call.
This patch installs a new event listener for gdb.events.inferior_call
and arranges for this to emit continue and stop events when
appropriate. It also fixes the original bug, by adding a check to
exec_and_expect_stop.
---
gdb/python/lib/gdb/dap/events.py | 26 +++++++++++++++++--
gdb/testsuite/gdb.dap/pause.c | 44 ++++++++++++++++++++++++++++++++
gdb/testsuite/gdb.dap/pause.exp | 30 +++++++++++++++++++++-
3 files changed, 97 insertions(+), 3 deletions(-)
create mode 100644 gdb/testsuite/gdb.dap/pause.c
Comments
>>>>> "Tom" == Tom Tromey <tromey@adacore.com> writes:
Tom> While working on cancellation, I noticed that a DAP 'pause' request
Tom> would set the "do not emit the continue" flag. This meant that a
Tom> subsequent request that should provoke a 'continue' event would
Tom> instead suppress the event.
Tom> I then tried writing a more obvious test case for this, involving an
Tom> inferior call -- and discovered that gdb.events.cont does not fire for
Tom> an inferior call.
Tom> This patch installs a new event listener for gdb.events.inferior_call
Tom> and arranges for this to emit continue and stop events when
Tom> appropriate. It also fixes the original bug, by adding a check to
Tom> exec_and_expect_stop.
I'm going to check this in on trunk & the gdb-14 branch now.
Tom
@@ -128,8 +128,9 @@ def exec_and_expect_stop(cmd, reason):
"""Indicate that a stop is expected, then execute CMD"""
global _expected_stop
_expected_stop = reason
- global _suppress_cont
- _suppress_cont = True
+ if reason != StopKinds.PAUSE:
+ global _suppress_cont
+ _suppress_cont = True
# FIXME if the call fails should we clear _suppress_cont?
exec_and_log(cmd)
@@ -156,6 +157,26 @@ def _on_stop(event):
send_event("stopped", obj)
+# This keeps a bit of state between the start of an inferior call and
+# the end. If the inferior was already running when the call started
+# (as can happen if a breakpoint condition calls a function), then we
+# do not want to emit 'continued' or 'stop' events for the call. Note
+# that, for some reason, gdb.events.cont does not fire for an infcall.
+_infcall_was_running = False
+
+
+@in_gdb_thread
+def _on_inferior_call(event):
+ global _infcall_was_running
+ if isinstance(event, gdb.InferiorCallPreEvent):
+ _infcall_was_running = inferior_running
+ if not _infcall_was_running:
+ _cont(None)
+ else:
+ if not _infcall_was_running:
+ _on_stop(None)
+
+
gdb.events.stop.connect(_on_stop)
gdb.events.exited.connect(_on_exit)
gdb.events.new_thread.connect(_new_thread)
@@ -163,3 +184,4 @@ gdb.events.thread_exited.connect(_thread_exited)
gdb.events.cont.connect(_cont)
gdb.events.new_objfile.connect(_new_objfile)
gdb.events.free_objfile.connect(_objfile_removed)
+gdb.events.inferior_call.connect(_on_inferior_call)
new file mode 100644
@@ -0,0 +1,44 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+ Copyright 2011-2023 Free Software Foundation, Inc.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
+
+#include <unistd.h>
+
+int
+do_nothing ()
+{
+ return 91;
+}
+
+int
+return_false ()
+{
+ return 0;
+}
+
+void
+sleep_a_bit ()
+{
+ sleep (1); /* STOP */
+}
+
+int
+main ()
+{
+ while (1)
+ sleep_a_bit ();
+ return 0;
+}
@@ -19,7 +19,7 @@ require allow_dap_tests
load_lib dap-support.exp
-standard_testfile attach.c
+standard_testfile
if {[build_executable ${testfile}.exp $testfile $srcfile] == -1} {
return
@@ -29,6 +29,18 @@ if {[dap_launch $testfile] == ""} {
return
}
+# Set a conditional breakpoint that will never fire. This is done to
+# test the state-tracking in events -- an inferior call from a
+# breakpoint condition should not cause any sort of stop or continue
+# events.
+set line [gdb_get_line_number "STOP"]
+dap_check_request_and_response "set conditional breakpoint" \
+ setBreakpoints \
+ [format {o source [o path [%s]] \
+ breakpoints [a [o line [i %d] \
+ condition [s "return_false()"]]]} \
+ [list s $srcfile] $line]
+
dap_check_request_and_response "start inferior" configurationDone
dap_wait_for_event_and_check "inferior started" thread "body reason" started
@@ -45,4 +57,20 @@ dap_check_request_and_response pause pause \
dap_wait_for_event_and_check "stopped by pause" stopped \
"body reason" pause
+set result [dap_request_and_response evaluate {o expression [s do_nothing()]}]
+gdb_assert {[dict get [lindex $result 0] body result] == 91} \
+ "check result of evaluation"
+
+set seen fail
+foreach event [lindex $result 1] {
+ if {[dict get $event type] != "event"} {
+ continue
+ }
+ if {[dict get $event event] == "continued"} {
+ set seen pass
+ break
+ }
+}
+gdb_assert {$seen == "pass"} "continue event from inferior call"
+
dap_shutdown