This is the mail archive of the
gdb-patches@sourceware.org
mailing list for the GDB project.
Re: [RFA] Reverse Debugging, 3/5
- From: Michael Snyder <msnyder at vmware dot com>
- To: Pedro Alves <pedro at codesourcery dot com>
- Cc: "gdb-patches at sourceware dot org" <gdb-patches at sourceware dot org>, Daniel Jacobowitz <drow at false dot org>, teawater <teawater at gmail dot com>
- Date: Mon, 06 Oct 2008 13:51:39 -0700
- Subject: Re: [RFA] Reverse Debugging, 3/5
- References: <48E3CD0B.8020003@vmware.com> <200810062109.16785.pedro@codesourcery.com>
Pedro Alves wrote:
Hi Michael,
Haven't read the other patches yet, but I'll go ahead and give
some comments on this one.
On Wednesday 01 October 2008 20:18:35, Michael Snyder wrote:
Index: infrun.c
===================================================================
RCS file: /cvs/src/src/gdb/infrun.c,v
retrieving revision 1.322
retrieving revision 1.322.2.2
diff -u -p -r1.322 -r1.322.2.2
--- infrun.c 22 Sep 2008 15:26:53 -0000 1.322
+++ infrun.c 30 Sep 2008 23:50:51 -0000 1.322.2.2
@@ -1193,11 +1193,17 @@ proceed (CORE_ADDR addr, enum target_sig
if (addr == (CORE_ADDR) -1)
{
- if (pc == stop_pc && breakpoint_here_p (pc))
+ if (pc == stop_pc && breakpoint_here_p (pc)
+ && target_get_execution_direction () != EXEC_REVERSE)
Hmmm, so EXEC_ERROR is accepted here. What exactly is
EXEC_ERROR useful for? Will there be a target that can't go
either direction? :-)
No, silly... ;-)
Shouldn't failing to find ones
direction always be an error (hence an error call from inside
target_get_execution_direction, or something alike).
Targets that don't implement reverse return EXEC_ERROR,
rather than EXEC_FORWARD. It was an early interface
design decision, and I'm not sure if I can remember the
justification after over 2 years, but I made it
consciously -- it seemed to simplify things.
/* The PTID we'll do a target_wait on.*/
@@ -2141,6 +2149,12 @@ handle_inferior_event (struct execution_
ecs->event_thread->stop_signal = ecs->ws.value.sig;
break;
+ case TARGET_WAITKIND_NO_HISTORY:
+ /* Reverse execution: target ran out of history info. */
+ print_stop_reason (NO_HISTORY, 0);
+ stop_stepping (ecs);
+ return;
+
/* We had an event in the inferior, but we are not interested
in handling it at this level. The lower layers have already
done what needs to be done, if anything.
@@ -2861,6 +2875,17 @@ infrun: BPSTAT_WHAT_SET_LONGJMP_RESUME (
keep_going (ecs);
return;
}
+ if (stop_pc == ecs->stop_func_start &&
+ target_get_execution_direction () == EXEC_REVERSE)
Split new line before the operator, not after:
OK
case BPSTAT_WHAT_CHECK_SHLIBS:
@@ -3026,10 +3051,25 @@ infrun: BPSTAT_WHAT_SET_LONGJMP_RESUME (
&& stop_pc < ecs->event_thread->step_range_end)
{
if (debug_infrun)
- fprintf_unfiltered (gdb_stdlog, "infrun: stepping inside range [0x%s-0x%s]\n",
+ fprintf_unfiltered (gdb_stdlog, "infrun: stepping inside range [0x%s-0x%s]\n",
paddr_nz (ecs->event_thread->step_range_start),
paddr_nz (ecs->event_thread->step_range_end));
- keep_going (ecs);
+
+ /* When stepping backward, stop at beginning of line range
+ (unles it's the function entry point, in which case
unless
OK
+ keep going back to the call point). */
+ if (stop_pc == ecs->event_thread->step_range_start &&
+ stop_pc != ecs->stop_func_start &&
+ target_get_execution_direction () == EXEC_REVERSE)
+ {
+ ecs->event_thread->stop_step = 1;
+ print_stop_reason (END_STEPPING_RANGE, 0);
+ stop_stepping (ecs);
+ }
+ else
+ {
+ keep_going (ecs);
+ }
Unneeded braces.
Don't you think it's more readable if the if block
and the else block match?
return;
}
@@ -3116,10 +3156,28 @@ infrun: BPSTAT_WHAT_SET_LONGJMP_RESUME (
if (ecs->event_thread->step_over_calls == STEP_OVER_ALL)
{
- /* We're doing a "next", set a breakpoint at callee's return
- address (the address at which the caller will
- resume). */
- insert_step_resume_breakpoint_at_caller (get_current_frame ());
+ /* We're doing a "next".
+
+ Normal (forward) execution: set a breakpoint at the
+ callee's return address (the address at which the caller
+ will resume).
+
+ Reverse (backward) execution. set the step-resume
+ breakpoint at the start of the function that we just
+ stepped into (backwards), and continue to there. When we
+ get there, we'll need to single-step back to the
+ caller. */
+
+ if (target_get_execution_direction () == EXEC_REVERSE)
+ {
+ struct symtab_and_line sr_sal;
+ init_sal (&sr_sal);
+ sr_sal.pc = ecs->stop_func_start;
+ insert_step_resume_breakpoint_at_sal (sr_sal, null_frame_id);
+ }
+ else
+ insert_step_resume_breakpoint_at_caller (get_current_frame ());
+
keep_going (ecs);
return;
}
@@ -3176,9 +3234,21 @@ infrun: BPSTAT_WHAT_SET_LONGJMP_RESUME (
return;
}
- /* Set a breakpoint at callee's return address (the address at
- which the caller will resume). */
- insert_step_resume_breakpoint_at_caller (get_current_frame ());
+ if (target_get_execution_direction () == EXEC_REVERSE)
+ {
+ /* Set a breakpoint at callee's start address.
+ From there we can step once and be back in the caller. */
+ struct symtab_and_line sr_sal;
+ init_sal (&sr_sal);
+ sr_sal.pc = ecs->stop_func_start;
+ insert_step_resume_breakpoint_at_sal (sr_sal, null_frame_id);
+ }
+ else
+ {
+ /* Set a breakpoint at callee's return address (the address
+ at which the caller will resume). */
+ insert_step_resume_breakpoint_at_caller (get_current_frame ());
+ }
Unneeded braces.
Oh come on -- I know they're syntactic null, but
they serve to keep the comment together with the
code it refers to.
keep_going (ecs);
return;
}
@@ -3344,6 +3414,28 @@ step_into_function (struct execution_con
ecs->stop_func_start = gdbarch_skip_prologue
(current_gdbarch, ecs->stop_func_start);
+ if (target_get_execution_direction () == EXEC_REVERSE)
+ {
+ stop_func_sal = find_pc_line (stop_pc, 0);
+
+ /* OK, we're just gonna keep stepping here. */
+ if (stop_func_sal.pc == stop_pc)
+ {
+ /* We're there already. Just stop stepping now. */
+ ecs->event_thread->stop_step = 1;
+ print_stop_reason (END_STEPPING_RANGE, 0);
+ stop_stepping (ecs);
+ return;
+ }
+ /* Else just reset the step range and keep going.
+ No step-resume breakpoint, they don't work for
+ epilogues, which can have multiple entry paths. */
+ ecs->event_thread->step_range_start = stop_func_sal.pc;
+ ecs->event_thread->step_range_end = stop_func_sal.end;
Somethings fishy with the whitespace. ^
I just like things to line up when possible!
;-)
+ keep_going (ecs);
+ return;
+ }
+ /* else... */
stop_func_sal = find_pc_line (ecs->stop_func_start, 0);
/* Use the step_resume_break to step until the end of the prologue,
even if that involves jumps (as it seems to on the vax under
@@ -3712,6 +3804,10 @@ print_stop_reason (enum inferior_stop_re
annotate_signal_string_end ();
ui_out_text (uiout, ".\n");
break;
+ case NO_HISTORY:
+ /* Reverse execution: target ran out of history info. */
+ ui_out_text (uiout, "\nNo more reverse-execution history.\n");
+ break;
default:
internal_error (__FILE__, __LINE__,
_("print_stop_reason: unrecognized enum value"));
Otherwise, I can't see anything wrong with it...
Thanks for reviewing.