Re: [RFA] Clarify infrun variable naming.

Vladimir Prus
2007-12-05T12:17:44Z

[-- Attachment #1: Type: text/plain, Size: 20396 bytes --]

On Wednesday 05 December 2007 04:17:52 Jim Blandy wrote:
>
> Vladimir Prus <vladimir at codesourcery.com> writes:
> > The infrun.c file has a variable named trap_expected, which
> > is a bit misleading -- after all, most times when we resume
> > inferior, we get SIGTRAP. As it turns out, that variable
> > is set when we're stepping over breakpoints, so a better
> > name would be stepping_over_breakpoint. Likewise,
> > ecs->another_trap also indicates that keep_going should
> > be stepping over breakpoint. The attached patch clarifies
> > the naming and adds comments, and has no behaviour changes.
> > (The patch is on top of my previous breakpoints_inserted
> > removing patch).
> > OK?
...
> So, my suggestions were:
>
> - We should replace stepping_past_breakpoint and
> stepping_past_breakpoint_ptid with a single ptid_t variable,
> deferred_step_ptid.
>
> - We should rename trap_expected to stepped_over_breakpoint. The past
> tense 'stepped' suggests that we're talking about a step which has
> already happened (which is true by the time we reach
> handle_inferior_event).
>
> (And if I meditate carefully enough on the best possible names, it'll
> be quite some time before I have to look at Vlad's harder patches. :))

Here's the patch that renamed stepping_past_breakpoint_ptid. I attach both
patch and the delta relative to the previous revision.

The 'stepped' vs. 'stepping' change was not done -- for reason I've posted
already.

OK?

- Volodya

* infrun.c (trap_expected): Rename
to stepping_over_breakpoint.  Document.
(stepping_past_breakpoint): Remove.
(stepping_past_breakpoint_ptdi): Renamed
to deferred_step_ptid.
(struct execution_control_state): Rename
the another_trap field to stepping_over_breakpoint.
(struct inferior_status): Rename the trap_expected
field to stepping_over_breakpoint.
(clear_proceed_status, proceed)
(init_execution_control_state, context_switch)
(handle_inferior_event, currently_stepping)
(keep_going, save_inferior_status)
(restore_inferior_status, prepare_to_proceed): Adjust.
* gdbthread.h (struct thread_info): Rename the
trap_expected field to stepping_over_breakpoint.
* thread.c (load_infrun_state, save_infrun_state):
Adjust.
---
gdb/gdbthread.h |    2 +-
gdb/infrun.c    |  117 ++++++++++++++++++++++++++++++++++---------------------
gdb/thread.c    |    8 ++--
3 files changed, 77 insertions(+), 50 deletions(-)

diff --git a/gdb/gdbthread.h b/gdb/gdbthread.h
index aeb4a40..12e0bcc 100644
--- a/gdb/gdbthread.h
+++ b/gdb/gdbthread.h
@@ -49,7 +49,7 @@ struct thread_info
struct symtab *current_symtab;
int trap_expected;
int handling_longjmp;
-  int another_trap;
+  int stepping_over_breakpoint;

/* This is set TRUE when a catchpoint of a shared library event
triggers.  Since we don't wish to leave the inferior in the
diff --git a/gdb/infrun.c b/gdb/infrun.c
index c608f72..77623b6 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -218,9 +218,30 @@ static struct cmd_list_element *stop_command;

static struct symbol *step_start_function;

-/* Nonzero if we are expecting a trace trap and should proceed from it.  */
+/* Nonzero if we are presenting stepping over breakpoint.

-static int trap_expected;
+   If we hit a breakpoint or watchpoint, and then continue,
+   we need to single step the current thread with breakpoints
+   disabled, so that to avoid hitting the same breakpoint or
+   watchpoint again.  And we should step just a single
+   thread and keep other threads stopped, so that
+   other threads don't miss breakpoints while they are removed.
+
+   So, this variable simultaneously means that we need to single
+   step current thread, keep other threads stopped, and that
+   breakpoints should be removed while we step.
+
+   This variable is set either:
+   - in proceed, when we resume inferior on explicit user's request
+   - in keep_going, if handle_inferior_event decides we need to
+   step over breakpoint.
+
+   The variable is cleared in clear_proceed_status, called every
+   time before we call proceed.  The proceed calls wait_for_inferior,
+   which calls handle_inferior_event in a loop, and until
+   wait_for_inferior exits, this variable is changed only by keep_going.  */
+
+static int stepping_over_breakpoint;

/* Nonzero if we want to give control to the user when we're notified
of shared library events by the dynamic linker.  */
@@ -442,10 +463,14 @@ static CORE_ADDR singlestep_pc;
static ptid_t saved_singlestep_ptid;
static int stepping_past_singlestep_breakpoint;

-/* Similarly, if we are stepping another thread past a breakpoint,
-   save the original thread here so that we can resume stepping it later.  */
-static ptid_t stepping_past_breakpoint_ptid;
-static int stepping_past_breakpoint;
+/* If not equal to null_ptid, means that after stepping over breakpoint
+   is finished, we need to switch to deferred_step_ptid, and step it.
+
+   The use case is when a breakpoint in one thread, and then the user
+   has switched to another thread and issued 'step'. We need to step over
+   breakpoint in the thread which hit breakpoint, but then continue
+   stepping the thread user has selected.  */
+static ptid_t deferred_step_ptid;

/* Things to clean up if we QUIT out of resume ().  */
@@ -647,7 +672,7 @@ a command like `return' or `jump' to continue execution."));
void
clear_proceed_status (void)
{
-  trap_expected = 0;
+  stepping_over_breakpoint = 0;
step_range_start = 0;
step_range_end = 0;
step_frame_id = null_frame_id;
@@ -693,8 +718,7 @@ prepare_to_proceed (int step)
/* If stepping, remember current thread to switch back to.  */
if (step)
{
-         stepping_past_breakpoint = 1;
-         stepping_past_breakpoint_ptid = inferior_ptid;
+         deferred_step_ptid = inferior_ptid;
}

/* Switch back to WAIT_PID thread.  */
@@ -778,7 +802,7 @@ proceed (CORE_ADDR addr, enum target_signal siggnal, int step)
if (oneproc)
/* We will get a trace trap after one instruction.
Continue it automatically and insert breakpoints then.  */
-    trap_expected = 1;
+    stepping_over_breakpoint = 1;
else
insert_breakpoints ();

@@ -842,7 +866,7 @@ start_remote (int from_tty)
init_thread_list ();
init_wait_for_inferior ();
stop_soon = STOP_QUIETLY_REMOTE;
-  trap_expected = 0;
+  stepping_over_breakpoint = 0;

/* Always go on waiting for the target, regardless of the mode. */
/* FIXME: cagney/1999-09-23: At present it isn't possible to
@@ -887,7 +911,7 @@ init_wait_for_inferior (void)
clear_proceed_status ();

stepping_past_singlestep_breakpoint = 0;
-  stepping_past_breakpoint = 0;
+  deferred_step_ptid = null_ptid;
}

/* This enum encodes possible reasons for doing a target_wait, so that
@@ -924,7 +948,9 @@ struct execution_control_state
{
struct target_waitstatus ws;
struct target_waitstatus *wp;
-  int another_trap;
+  /* Should we step over breakpoint next time keep_going
+     is called?  */
+  int stepping_over_breakpoint;
int random_signal;
CORE_ADDR stop_func_start;
CORE_ADDR stop_func_end;
@@ -1085,7 +1111,7 @@ fetch_inferior_event (void *client_data)
void
init_execution_control_state (struct execution_control_state *ecs)
{
-  ecs->another_trap = 0;
+  ecs->stepping_over_breakpoint = 0;
ecs->random_signal = 0;
ecs->step_after_step_resume_breakpoint = 0;
ecs->handling_longjmp = 0;   /* FIXME */
@@ -1140,20 +1166,20 @@ context_switch (struct execution_control_state *ecs)
{                          /* Perform infrun state context switch: */
/* Save infrun state for the old thread.  */
save_infrun_state (inferior_ptid, prev_pc,
-                        trap_expected, step_resume_breakpoint,
+                        stepping_over_breakpoint, step_resume_breakpoint,
step_range_start,
step_range_end, &step_frame_id,
-                        ecs->handling_longjmp, ecs->another_trap,
+                        ecs->handling_longjmp, ecs->stepping_over_breakpoint,
ecs->stepping_through_solib_after_catch,
ecs->stepping_through_solib_catchpoints,
ecs->current_line, ecs->current_symtab);

/* Load infrun state for the new thread.  */
load_infrun_state (ecs->ptid, &prev_pc,
-                        &trap_expected, &step_resume_breakpoint,
+                        &stepping_over_breakpoint, &step_resume_breakpoint,
&step_range_start,
&step_range_end, &step_frame_id,
-                        &ecs->handling_longjmp, &ecs->another_trap,
+                        &ecs->handling_longjmp, &ecs->stepping_over_breakpoint,
&ecs->stepping_through_solib_after_catch,
&ecs->stepping_through_solib_catchpoints,
&ecs->current_line, &ecs->current_symtab);
@@ -1620,17 +1646,15 @@ handle_inferior_event (struct execution_control_state *ecs)

stepping_past_singlestep_breakpoint = 0;

-  if (stepping_past_breakpoint)
+  if (!ptid_equal (deferred_step_ptid, null_ptid))
{
-      stepping_past_breakpoint = 0;
-
/* If we stopped for some other reason than single-stepping, ignore
the fact that we were supposed to switch back.  */
if (stop_signal == TARGET_SIGNAL_TRAP)
{
if (debug_infrun)
fprintf_unfiltered (gdb_stdlog,
-                               "infrun: stepping_past_breakpoint\n");
+                               "infrun: handling deferred step\n");

/* Pull the single step breakpoints out of the target.  */
if (singlestep_breakpoints_inserted_p)
@@ -1641,7 +1665,8 @@ handle_inferior_event (struct execution_control_state *ecs)

/* Note: We do not call context_switch at this point, as the
context is already set up for stepping the original thread.  */
-         switch_to_thread (stepping_past_breakpoint_ptid);
+         switch_to_thread (deferred_step_ptid);
+         deferred_step_ptid = null_ptid;
/* Suppress spurious "Switching to ..." message.  */
previous_inferior_ptid = inferior_ptid;

@@ -1649,6 +1674,8 @@ handle_inferior_event (struct execution_control_state *ecs)
prepare_to_wait (ecs);
return;
}
+
+      deferred_step_ptid = null_ptid;
}

/* See if a thread hit a thread-specific breakpoint that was meant for
@@ -1779,7 +1806,7 @@ handle_inferior_event (struct execution_control_state *ecs)
context_switch (ecs);
ecs->waiton_ptid = ecs->ptid;
ecs->wp = &(ecs->ws);
-             ecs->another_trap = 1;
+             ecs->stepping_over_breakpoint = 1;

ecs->infwait_state = infwait_thread_hop_state;
keep_going (ecs);
@@ -1870,7 +1897,7 @@ handle_inferior_event (struct execution_control_state *ecs)
&ecs->stop_func_start, &ecs->stop_func_end);
ecs->stop_func_start
+= gdbarch_deprecated_function_start_offset (current_gdbarch);
-  ecs->another_trap = 0;
+  ecs->stepping_over_breakpoint = 0;
bpstat_clear (&stop_bpstat);
stop_step = 0;
stop_stack_dummy = 0;
@@ -1879,7 +1906,7 @@ handle_inferior_event (struct execution_control_state *ecs)
stopped_by_random_signal = 0;

if (stop_signal == TARGET_SIGNAL_TRAP
-      && trap_expected
+      && stepping_over_breakpoint
&& gdbarch_single_step_through_delay_p (current_gdbarch)
&& currently_stepping (ecs))
{
@@ -1897,7 +1924,7 @@ handle_inferior_event (struct execution_control_state *ecs)
{
/* The user issued a continue when stopped at a breakpoint.
Set up for another trap and get out of here.  */
-         ecs->another_trap = 1;
+         ecs->stepping_over_breakpoint = 1;
keep_going (ecs);
return;
}
@@ -1906,10 +1933,10 @@ handle_inferior_event (struct execution_control_state *ecs)
/* The user issued a step when stopped at a breakpoint.
Maybe we should stop, maybe we should not - the delay
slot *might* correspond to a line of source.  In any
-            case, don't decide that here, just set ecs->another_trap,
-            making sure we single-step again before breakpoints are
-            re-inserted.  */
-         ecs->another_trap = 1;
+            case, don't decide that here, just set
+            ecs->stepping_over_breakpoint, making sure we
+            single-step again before breakpoints are re-inserted.  */
+         ecs->stepping_over_breakpoint = 1;
}
}

@@ -1917,7 +1944,7 @@ handle_inferior_event (struct execution_control_state *ecs)
The alternatives are:
1) break; to really stop and return to the debugger,
2) drop through to start up again
-     (set ecs->another_trap to 1 to single step once)
+     (set ecs->stepping_over_breakpoint to 1 to single step once)
3) set ecs->random_signal to 1, and the decision between 1 and 2
will be made according to the signal handling tables.  */

@@ -2001,7 +2028,7 @@ handle_inferior_event (struct execution_control_state *ecs)
if (stop_signal == TARGET_SIGNAL_TRAP)
ecs->random_signal
= !(bpstat_explains_signal (stop_bpstat)
-             || trap_expected
+             || stepping_over_breakpoint
|| (step_range_end && step_resume_breakpoint == NULL));
else
{
@@ -2162,7 +2189,7 @@ process_event_stop_test:
if (debug_infrun)
fprintf_unfiltered (gdb_stdlog, "infrun: BPSTAT_WHAT_SINGLE\n");
remove_breakpoints ();
-       ecs->another_trap = 1;
+       ecs->stepping_over_breakpoint = 1;
/* Still need to check other stuff, at least the case
where we are stepping and step out of the right range.  */
break;
@@ -2223,7 +2250,7 @@ process_event_stop_test:
to doing that.  */
ecs->step_after_step_resume_breakpoint = 0;
remove_breakpoints ();
-           ecs->another_trap = 1;
+           ecs->stepping_over_breakpoint = 1;
keep_going (ecs);
return;
}
@@ -2308,13 +2335,13 @@ process_event_stop_test:

/* Be sure to lift all breakpoints, so the inferior does
actually step past this point... */
-             ecs->another_trap = 1;
+             ecs->stepping_over_breakpoint = 1;
break;
}
else
{
/* We want to step over this breakpoint, then keep going.  */
-             ecs->another_trap = 1;
+             ecs->stepping_over_breakpoint = 1;
break;
}
}
@@ -2345,7 +2372,7 @@ process_event_stop_test:
{
if (debug_infrun)
fprintf_unfiltered (gdb_stdlog, "infrun: stepping in dynamic linker\n");
-         ecs->another_trap = 1;
+         ecs->stepping_over_breakpoint = 1;
keep_going (ecs);
return;
}
@@ -2741,7 +2768,7 @@ currently_stepping (struct execution_control_state *ecs)
{
return ((!ecs->handling_longjmp
&& ((step_range_end && step_resume_breakpoint == NULL)
-              || trap_expected))
+              || stepping_over_breakpoint))
|| ecs->stepping_through_solib_after_catch
|| bpstat_should_step ());
}
@@ -2920,7 +2947,7 @@ keep_going (struct execution_control_state *ecs)
/* If we did not do break;, it means we should keep running the
inferior and not return to debugger.  */

-  if (trap_expected && stop_signal != TARGET_SIGNAL_TRAP)
+  if (stepping_over_breakpoint && stop_signal != TARGET_SIGNAL_TRAP)
{
/* We took a signal (which we are supposed to pass through to
the inferior, else we'd have done a break above) and we
@@ -2942,7 +2969,7 @@ keep_going (struct execution_control_state *ecs)
already inserted breakpoints.  Therefore, we don't
care if breakpoints were already inserted, or not.  */

-      if (!ecs->another_trap)
+      if (!ecs->stepping_over_breakpoint)
{
struct gdb_exception e;
/* Stop stepping when inserting breakpoints
@@ -2958,7 +2985,7 @@ keep_going (struct execution_control_state *ecs)
}
}

-      trap_expected = ecs->another_trap;
+      stepping_over_breakpoint = ecs->stepping_over_breakpoint;

/* Do not deliver SIGNAL_TRAP (except when the user explicitly
specifies that such a signal should be delivered to the
@@ -3676,7 +3703,7 @@ struct inferior_status
int stop_step;
int stop_stack_dummy;
int stopped_by_random_signal;
-  int trap_expected;
+  int stepping_over_breakpoint;
CORE_ADDR step_range_start;
CORE_ADDR step_range_end;
struct frame_id step_frame_id;
@@ -3722,7 +3749,7 @@ save_inferior_status (int restore_stack_info)
inf_status->stop_step = stop_step;
inf_status->stop_stack_dummy = stop_stack_dummy;
inf_status->stopped_by_random_signal = stopped_by_random_signal;
-  inf_status->trap_expected = trap_expected;
+  inf_status->stepping_over_breakpoint = stepping_over_breakpoint;
inf_status->step_range_start = step_range_start;
inf_status->step_range_end = step_range_end;
inf_status->step_frame_id = step_frame_id;
@@ -3774,7 +3801,7 @@ restore_inferior_status (struct inferior_status *inf_status)
stop_step = inf_status->stop_step;
stop_stack_dummy = inf_status->stop_stack_dummy;
stopped_by_random_signal = inf_status->stopped_by_random_signal;
-  trap_expected = inf_status->trap_expected;
+  stepping_over_breakpoint = inf_status->stepping_over_breakpoint;
step_range_start = inf_status->step_range_start;
step_range_end = inf_status->step_range_end;
step_frame_id = inf_status->step_frame_id;
diff --git a/gdb/thread.c b/gdb/thread.c
index b6762e1..3c8644b 100644
--- a/gdb/thread.c
+++ b/gdb/thread.c
@@ -300,7 +300,7 @@ load_infrun_state (ptid_t ptid,
CORE_ADDR *step_range_end,
struct frame_id *step_frame_id,
int *handling_longjmp,
-                  int *another_trap,
+                  int *stepping_over_breakpoint,
int *stepping_through_solib_after_catch,
bpstat *stepping_through_solib_catchpoints,
int *current_line,
@@ -321,7 +321,7 @@ load_infrun_state (ptid_t ptid,
*step_range_end = tp->step_range_end;
*step_frame_id = tp->step_frame_id;
*handling_longjmp = tp->handling_longjmp;
-  *another_trap = tp->another_trap;
+  *stepping_over_breakpoint = tp->stepping_over_breakpoint;
*stepping_through_solib_after_catch =
tp->stepping_through_solib_after_catch;
*stepping_through_solib_catchpoints =
@@ -341,7 +341,7 @@ save_infrun_state (ptid_t ptid,
CORE_ADDR step_range_end,
const struct frame_id *step_frame_id,
int handling_longjmp,
-                  int another_trap,
+                  int stepping_over_breakpoint,
int stepping_through_solib_after_catch,
bpstat stepping_through_solib_catchpoints,
int current_line,
@@ -362,7 +362,7 @@ save_infrun_state (ptid_t ptid,
tp->step_range_end = step_range_end;
tp->step_frame_id = (*step_frame_id);
tp->handling_longjmp = handling_longjmp;
-  tp->another_trap = another_trap;
+  tp->stepping_over_breakpoint = stepping_over_breakpoint;
tp->stepping_through_solib_after_catch = stepping_through_solib_after_catch;
tp->stepping_through_solib_catchpoints = stepping_through_solib_catchpoints;
tp->current_line = current_line;
--
1.5.3.5

[-- Attachment #2: delta.diff --]
[-- Type: text/x-diff, Size: 2977 bytes --]

diff --git a/gdb/infrun.c b/gdb/infrun.c
index 043d8f1..77623b6 100644
--- a/gdb/infrun.c
+++ b/gdb/infrun.c
@@ -463,10 +463,14 @@ static CORE_ADDR singlestep_pc;
static ptid_t saved_singlestep_ptid;
static int stepping_past_singlestep_breakpoint;

-/* Similarly, if we are stepping another thread past a breakpoint,
- save the original thread here so that we can resume stepping it later. */
-static ptid_t stepping_past_breakpoint_ptid;
-static int stepping_past_breakpoint;
+/* If not equal to null_ptid, means that after stepping over breakpoint
+ is finished, we need to switch to deferred_step_ptid, and step it.
+
+ The use case is when a breakpoint in one thread, and then the user
+ has switched to another thread and issued 'step'. We need to step over
+ breakpoint in the thread which hit breakpoint, but then continue
+ stepping the thread user has selected. */
+static ptid_t deferred_step_ptid;
\f

/* Things to clean up if we QUIT out of resume (). */
@@ -714,8 +718,7 @@ prepare_to_proceed (int step)
/* If stepping, remember current thread to switch back to. */
if (step)
{
- stepping_past_breakpoint = 1;
- stepping_past_breakpoint_ptid = inferior_ptid;
+ deferred_step_ptid = inferior_ptid;
}

/* Switch back to WAIT_PID thread. */
@@ -908,7 +911,7 @@ init_wait_for_inferior (void)
clear_proceed_status ();

stepping_past_singlestep_breakpoint = 0;
- stepping_past_breakpoint = 0;
+ deferred_step_ptid = null_ptid;
}
\f
/* This enum encodes possible reasons for doing a target_wait, so that
@@ -1643,17 +1646,15 @@ handle_inferior_event (struct execution_control_state *ecs)

stepping_past_singlestep_breakpoint = 0;

- if (stepping_past_breakpoint)
+ if (!ptid_equal (deferred_step_ptid, null_ptid))
{
- stepping_past_breakpoint = 0;
-
/* If we stopped for some other reason than single-stepping, ignore
the fact that we were supposed to switch back. */
if (stop_signal == TARGET_SIGNAL_TRAP)
{
if (debug_infrun)
fprintf_unfiltered (gdb_stdlog,
- "infrun: stepping_past_breakpoint\n");
+ "infrun: handling deferred step\n");

/* Pull the single step breakpoints out of the target. */
if (singlestep_breakpoints_inserted_p)
@@ -1664,7 +1665,8 @@ handle_inferior_event (struct execution_control_state *ecs)

/* Note: We do not call context_switch at this point, as the
context is already set up for stepping the original thread. */
- switch_to_thread (stepping_past_breakpoint_ptid);
+ switch_to_thread (deferred_step_ptid);
+ deferred_step_ptid = null_ptid;
/* Suppress spurious "Switching to ..." message. */
previous_inferior_ptid = inferior_ptid;

@@ -1672,6 +1674,8 @@ handle_inferior_event (struct execution_control_state *ecs)
prepare_to_wait (ecs);
return;
}
+
+ deferred_step_ptid = null_ptid;
}

/* See if a thread hit a thread-specific breakpoint that was meant for