Re: [PATCH] Reset tracepoint step_count to 0 before set it action

[Pedro Alves <palves at redhat dot com>]

On 04/04/2013 07:30 PM, Pedro Alves wrote:

> Here's what I'm checking in.

On 03/24/2013 11:32 AM, Hui Zhu wrote:
> And I suggest this change can be checked to 7.6 branch.

I think it's safe enough, so I went ahead and put it in the branch as well.

Here it is again, now with full commit log.  The 7.6 version
had a minor adjustment as validate_actionline's prototype
is slightly different there.

--------------
tracepoint->step_count fixes

If a tracepoint's actions list includes a while-stepping action, and
then the actions are changed to a list without any while-stepping
action, the tracepoint's step_count will be left with a stale value.
For example:

 (gdb) trace subr
 Tracepoint 1 at 0x4004d9: file ../../../src/gdb/testsuite//actions-changed.c, line 31.
 (gdb) actions
 Enter actions for tracepoint 1, one per line.
 End with a line saying just "end".
 >collect $reg
 >end
 (gdb) set debug remote 1
 (gdb) tstart
 Sending packet: $QTinit#59...Packet received: OK
 Sending packet: $QTDP:1:00000000004004d9:E:0:0-#a3...Packet received: OK
 Sending packet: $QTDP:-1:00000000004004d9:R03FFFFFFFFFFFFFFFFFF#2b...Packet received: OK
 (gdb) tstop
 Sending packet: $QTStop#4b...Packet received: OK
 Sending packet: $QTNotes:#e8...Packet received: OK
 (gdb) actions
 Enter actions for tracepoint 1, one per line.
 End with a line saying just "end".
 >collect $reg
 >while-stepping 1
   >collect $reg
   >end
 >end
 (gdb) tstart
 Sending packet: $QTinit#59...Packet received: OK
 Sending packet: $QTDP:1:00000000004004d9:E:1:0-#a4...Packet received: OK
 Sending packet: $QTDP:-1:00000000004004d9:R03FFFFFFFFFFFFFFFFFF-#58...Packet received: OK
 Sending packet: $QTDP:-1:00000000004004d9:SR03FFFFFFFFFFFFFFFFFF#7e...Packet received: OK
 (gdb) tstop
 Sending packet: $QTStop#4b...Packet received: OK
 Sending packet: $QTNotes:#e8...Packet received: OK
 (gdb) actions
 Enter actions for tracepoint 1, one per line.
 End with a line saying just "end".
 >collect $regs
 >end
 (gdb) tstart
 Sending packet: $QTinit#59...Packet received: OK
 Sending packet: $QTDP:1:00000000004004d9:E:1:0-#a4...Packet received: OK
 Sending packet: $QTDP:-1:00000000004004d9:R03FFFFFFFFFFFFFFFFFF#2b...Packet received: OK

The last "$QTDP:1:00000000004004d9:E:1:0-#a4" should be "$QTDP:1:00000000004004d9:E:0:0-#a3".
In pseudo-diff:

  -$QTDP:1:00000000004004d9:E:1:0-#a4
  +$QTDP:1:00000000004004d9:E:0:0-#a3

A related issue is that the "commands" command actually supports
setting commands to a range of breakpoints/tracepoints at once.  But,
hacking "maint info breakpoints" to print t->step_count, reveals:

 (gdb) trace main
 Tracepoint 5 at 0x45a2ab: file ../../src/gdb/gdb.c, line 29.
 (gdb) trace main
 Note: breakpoint 5 also set at pc 0x45a2ab.
 Tracepoint 6 at 0x45a2ab: file ../../src/gdb/gdb.c, line 29.
 (gdb) commands 5-6
 Type commands for breakpoint(s) 5-6, one per line.
 End with a line saying just "end".
 > while-stepping 5
  >end
 > end
 (gdb) maint info breakpoints 5
 Num     Type           Disp Enb Address            What
 5       tracepoint     keep y   0x000000000045a2ab in main at ../../src/gdb/gdb.c:29 inf 1
         step_count=5
         ^^^^^^^^^^^^
         while-stepping 5
         end
         not installed on target
 (gdb) maint info breakpoints 6
 Num     Type           Disp Enb Address            What
 6       tracepoint     keep y   0x000000000045a2ab in main at ../../src/gdb/gdb.c:29 inf 1
         step_count=0
         ^^^^^^^^^^^^
         while-stepping 5
         end
         not installed on target
 (gdb)

that tracepoint 6 doesn't end up with the correct step_count.

The issue is that here:

 static void
 do_map_commands_command (struct breakpoint *b, void *data)
 {
  struct commands_info *info = data;

  if (info->cmd == NULL)
    {
      struct command_line *l;

      if (info->control != NULL)
	l = copy_command_lines (info->control->body_list[0]);
      else
	{
	  struct cleanup *old_chain;
	  char *str;

	  str = xstrprintf (_("Type commands for breakpoint(s) "
			      "%s, one per line."),
			    info->arg);

	  old_chain = make_cleanup (xfree, str);

	  l = read_command_lines (str,
				  info->from_tty, 1,
				  (is_tracepoint (b)
				   ? check_tracepoint_command : 0),
				  b);

	  do_cleanups (old_chain);
	}

      info->cmd = alloc_counted_command_line (l);
    }

validate_actionline is never called for tracepoints other than the
first (the copy_command_lines path).  Right below, we have:

  /* If a breakpoint was on the list more than once, we don't need to
     do anything.  */
  if (b->commands != info->cmd)
    {
      validate_commands_for_breakpoint (b, info->cmd->commands);
      incref_counted_command_line (info->cmd);
      decref_counted_command_line (&b->commands);
      b->commands = info->cmd;
      observer_notify_breakpoint_modified (b);
    }

And validate_commands_for_breakpoint looks like the right place to put
a call; if we reset step_count there too, we have a nice central fix
for the first issue as well, because trace_actions_command calls
breakpoint_set_commands that also calls
validate_commands_for_breakpoint.

We end up calling validate_actionline twice for the first tracepoint,
since read_command_lines calls it too, through
check_tracepoint_command, but that should be harmless.

2013-04-04  Pedro Alves  <palves@redhat.com>
	    Hui Zhu  <hui@codesourcery.com>

	* breakpoint.c (validate_commands_for_breakpoint): If validating a
	tracepoint, reset its STEP_COUNT and call validate_actionline.

2013-04-04  Stan Shebs  <stan@codesourcery.com>
	    Pedro Alves  <palves@redhat.com>

	* gdb.trace/Makefile.in (PROGS): Add actions-changed.
	* gdb.trace/actions-changed.c: New file.
	* gdb.trace/actions-changed.exp: New file.
	* lib/trace-support.exp (gdb_trace_setactions): Rename to ...
	(gdb_trace_setactions_command): ... this.  Add "actions_command"
	parameter, and handle it.
	(gdb_trace_setactions, gdb_trace_setcommands): New procedures.
---

 gdb/breakpoint.c                            |   23 +++-
 gdb/testsuite/gdb.trace/Makefile.in         |    6 -
 gdb/testsuite/gdb.trace/actions-changed.c   |   66 ++++++++++
 gdb/testsuite/gdb.trace/actions-changed.exp |  174 +++++++++++++++++++++++++++
 gdb/testsuite/lib/trace-support.exp         |   24 +++-
 5 files changed, 281 insertions(+), 12 deletions(-)
 create mode 100644 gdb/testsuite/gdb.trace/actions-changed.c
 create mode 100644 gdb/testsuite/gdb.trace/actions-changed.exp

diff --git a/gdb/breakpoint.c b/gdb/breakpoint.c
index ff161a0..5ba1f2f 100644
--- a/gdb/breakpoint.c
+++ b/gdb/breakpoint.c
@@ -1142,12 +1142,25 @@ validate_commands_for_breakpoint (struct breakpoint *b,
 {
   if (is_tracepoint (b))
     {
-      /* We need to verify that each top-level element of commands is
-	 valid for tracepoints, that there's at most one
-	 while-stepping element, and that while-stepping's body has
-	 valid tracing commands excluding nested while-stepping.  */
+      struct tracepoint *t = (struct tracepoint *) b;
       struct command_line *c;
       struct command_line *while_stepping = 0;
+
+      /* Reset the while-stepping step count.  The previous commands
+         might have included a while-stepping action, while the new
+         ones might not.  */
+      t->step_count = 0;
+
+      /* We need to verify that each top-level element of commands is
+	 valid for tracepoints, that there's at most one
+	 while-stepping element, and that the while-stepping's body
+	 has valid tracing commands excluding nested while-stepping.
+	 We also need to validate the tracepoint action line in the
+	 context of the tracepoint --- validate_actionline actually
+	 has side effects, like setting the tracepoint's
+	 while-stepping STEP_COUNT, in addition to checking if the
+	 collect/teval actions parse and make sense in the
+	 tracepoint's context.  */
       for (c = commands; c; c = c->next)
 	{
 	  if (c->control_type == while_stepping_control)
@@ -1165,6 +1178,8 @@ validate_commands_for_breakpoint (struct breakpoint *b,
 	      else
 		while_stepping = c;
 	    }
+
+	  validate_actionline (c->line, b);
 	}
       if (while_stepping)
 	{
diff --git a/gdb/testsuite/gdb.trace/Makefile.in b/gdb/testsuite/gdb.trace/Makefile.in
index 8a7d523..2e23223 100644
--- a/gdb/testsuite/gdb.trace/Makefile.in
+++ b/gdb/testsuite/gdb.trace/Makefile.in
@@ -3,9 +3,9 @@ srcdir = @srcdir@
 
 .PHONY: all clean mostlyclean distclean realclean
 
-PROGS = ax backtrace deltrace disconnected-tracing infotrace packetlen \
-	passc-dyn passcount report save-trace tfile tfind tracecmd tsv \
-	unavailable while-dyn while-stepping
+PROGS = actions-changed ax backtrace deltrace disconnected-tracing \
+	infotrace packetlen passc-dyn passcount report save-trace tfile \
+	tfind tracecmd tsv unavailable while-dyn while-stepping
 
 all info install-info dvi install uninstall installcheck check:
 	@echo "Nothing to be done for $@..."
diff --git a/gdb/testsuite/gdb.trace/actions-changed.c b/gdb/testsuite/gdb.trace/actions-changed.c
new file mode 100644
index 0000000..bac24a7
--- /dev/null
+++ b/gdb/testsuite/gdb.trace/actions-changed.c
@@ -0,0 +1,66 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2013 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/>.  */
+
+int
+end (int i)
+{
+}
+
+int
+subr2 (int parm)
+{
+  int keeping, busy;
+
+  keeping = parm + parm;
+  busy = keeping * keeping;
+
+  return busy;
+}
+
+int
+subr (int parm)
+{
+  int keeping, busy;
+
+  keeping = parm + parm;
+  busy = keeping * keeping;
+
+  return busy;
+}
+
+main()
+{
+  subr (1);
+  end (1);
+
+  subr (2);
+  end (2);
+
+  subr (3);
+  end (3);
+
+  subr (4);
+  end (4);
+
+  subr (5);
+  subr2 (5);
+  end (5);
+
+  subr (6);
+  subr2 (6);
+  end (6);
+}
diff --git a/gdb/testsuite/gdb.trace/actions-changed.exp b/gdb/testsuite/gdb.trace/actions-changed.exp
new file mode 100644
index 0000000..e850da2
--- /dev/null
+++ b/gdb/testsuite/gdb.trace/actions-changed.exp
@@ -0,0 +1,174 @@
+# Copyright 2013 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/>.
+
+load_lib trace-support.exp
+
+standard_testfile
+
+if {[prepare_for_testing $testfile.exp $testfile $srcfile debug]} {
+    return -1
+}
+
+proc test_actions_changed { } {
+    gdb_breakpoint "end"
+
+    gdb_test "trace subr" "Tracepoint .*" \
+	"tracepoint at subr"
+
+    # The first set of tests are regression tests for a GDB bug where
+    # the while-stepping count of a tracepoint would be left stale if
+    # the tracepoint's actions were redefined, and the new action list
+    # had no while-stepping action.
+
+    # First pass, define simple action.
+    with_test_prefix "1" {
+	gdb_trace_setactions "define simple action" \
+	    "" \
+	    "collect parm" "^$"
+
+	gdb_test_no_output "tstart"
+
+	gdb_test "continue" ".*Breakpoint \[0-9\]+, end \\(i=1\\) .*" \
+	    "advance through tracing"
+
+	gdb_test "tstatus" ".*Collected 1 trace frame.*" \
+	    "collected 1 trace frame"
+
+	gdb_test_no_output "tstop"
+    }
+
+    # Redefine action, run second trace.
+    with_test_prefix "2" {
+	gdb_trace_setactions "redefine simple action" \
+	    "" \
+	    "collect keeping, busy" "^$"
+
+	gdb_test_no_output "tstart"
+
+	gdb_test "continue" ".*Breakpoint \[0-9\]+, end \\(i=2\\) .*" \
+	    "advance through tracing"
+
+	gdb_test "tstatus" ".*Collected 1 trace frame.*" \
+	    "collected 1 trace frame"
+
+	gdb_test_no_output "tstop"
+    }
+
+    # Redefine to stepping action, run third trace.
+    with_test_prefix "3" {
+	gdb_trace_setactions "redefine to stepping action" \
+	    "" \
+	    "collect parm" "^$" \
+	    "while-stepping 5" "^$" \
+	    "collect parm" "^$" \
+	    "end" "^$"
+
+	gdb_test_no_output "tstart"
+
+	gdb_test "continue" ".*Breakpoint \[0-9\]+, end \\(i=3\\) .*" \
+	    "advance through tracing"
+
+	gdb_test "tstatus" ".*Collected 6 trace frames.*" \
+	    "collected 6 trace frames"
+
+	gdb_test_no_output "tstop"
+    }
+
+    # Redefine to non-stepping, run fourth trace.
+    with_test_prefix "4" {
+	gdb_trace_setactions "redefine to non-stepping action" \
+	    "" \
+	    "collect parm" "^$"
+
+	gdb_test_no_output "tstart"
+
+	gdb_test "continue" ".*Breakpoint \[0-9\]+, end \\(i=4\\) .*" \
+	    "advance through tracing"
+
+	gdb_test "tstatus" ".*Collected 1 trace frame.*" \
+	    "collected 1 trace frame"
+
+	gdb_test_no_output "tstop"
+    }
+
+    # The following tests are related to the above, but use two
+    # tracepoints.  They are regression tests for a GDB bug where only
+    # the first tracepoint would end up with the step count set.
+
+    # Store the first tracepoint's number.
+    gdb_test_no_output "set \$prev_tpnum=\$tpnum" "store previous \$tpnum"
+
+    # And here's the second tracepoint.
+    gdb_test "trace subr2" "Tracepoint .*" "tracepoint at subr2"
+
+    # Set a stepping action in both tracepoints, with the "commands"
+    # command.
+    with_test_prefix "5" {
+	gdb_trace_setcommands \
+	    "redefine 2 tracepoints to stepping action, using commands" \
+	    "\$prev_tpnum-\$tpnum" \
+	    "collect parm" "^$" \
+	    "while-stepping 5" "^$" \
+	    "collect parm" "^$" \
+	    "end" "^$"
+
+	gdb_test_no_output "tstart"
+
+	gdb_test "continue" ".*Breakpoint \[0-9\]+, end \\(i=5\\) .*" \
+	    "advance through tracing"
+
+	gdb_test "tstatus" ".*Collected 12 trace frames.*" \
+	    "collected 12 trace frames"
+
+	gdb_test_no_output "tstop"
+    }
+
+    # Redefine the actions of both tracepoints to non-stepping, also
+    # using the "commands" command.
+    with_test_prefix "6" {
+	gdb_trace_setcommands \
+	    "redefine 2 tracepoints to non-stepping action, using commands" \
+	    "\$prev_tpnum-\$tpnum" \
+	    "collect parm" "^$"
+
+	gdb_test_no_output "tstart"
+
+	gdb_test "continue" ".*Breakpoint \[0-9\]+, end \\(i=6\\) .*" \
+	    "advance through tracing"
+
+	gdb_test "tstatus" ".*Collected 2 trace frame.*" \
+	    "collected 2 trace frames"
+
+	gdb_test_no_output "tstop"
+    }
+}
+
+# Check whether the target supports tracepoints.
+
+clean_restart $testfile
+
+if ![runto_main] {
+    fail "Can't run to main to check for trace support"
+    return -1
+}
+
+if ![gdb_target_supports_trace] {
+    unsupported "Current target does not support trace"
+    return -1;
+}
+
+test_actions_changed
+
+return 0
diff --git a/gdb/testsuite/lib/trace-support.exp b/gdb/testsuite/lib/trace-support.exp
index 10482b8..2601ad8 100644
--- a/gdb/testsuite/lib/trace-support.exp
+++ b/gdb/testsuite/lib/trace-support.exp
@@ -86,23 +86,23 @@ proc gdb_delete_tracepoints {} {
     }
 }
 
-#
-# Procedure: gdb_trace_setactions
 #   Define actions for a tracepoint.
 #   Arguments:
+#       actions_command -- the command used to create the actions.
+#                          either "actions" or "commands".
 #	testname   -- identifying string for pass/fail output
-#	tracepoint -- to which tracepoint do these actions apply? (optional)
+#	tracepoint -- to which tracepoint(s) do these actions apply? (optional)
 #	args       -- list of actions to be defined.
 #   Returns:
 #	zero       -- success
 #	non-zero   -- failure
 
-proc gdb_trace_setactions { testname tracepoint args } {
+proc gdb_trace_setactions_command { actions_command testname tracepoint args } {
     global gdb_prompt;
 
     set state 0;
     set passfail "pass";
-    send_gdb "actions $tracepoint\n";
+    send_gdb "$actions_command $tracepoint\n";
     set expected_result "";
     gdb_expect 5 {
 	-re "No tracepoint number .*$gdb_prompt $" {
@@ -165,6 +165,20 @@ proc gdb_trace_setactions { testname tracepoint args } {
     }
 }
 
+# Define actions for a tracepoint, using the "actions" command.  See
+# gdb_trace_setactions_command.
+#
+proc gdb_trace_setactions { testname tracepoint args } {
+    eval gdb_trace_setactions_command "actions" {$testname} {$tracepoint} $args
+}
+
+# Define actions for a tracepoint, using the "commands" command.  See
+# gdb_trace_setactions_command.
+#
+proc gdb_trace_setcommands { testname tracepoint args } {
+    eval gdb_trace_setactions_command "commands" {$testname} {$tracepoint} $args
+}
+
 #
 # Procedure: gdb_tfind_test
 #   Find a specified trace frame.