Re: [reverse RFA] no singlestep-over-BP in reverse

Michael Snyder
2008-09-17T00:56:41Z

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Joel Brobecker wrote:
>> And I believe that consistent behavior / semantics should be:
>>
>> If you tell me that you are stopped at instruction 1000,
>> regardless of whether you were going forward or backward
>> when you got there, then I will expect that if I tell you
>> to execute forward, you will execute the instruction at
>> 1000.
>
> This makes total sense to me. I think I would be very confused
> by the debugger if I started going back and forth with a debugger
> that didn't follow the semantics above.

Thanks. By the way I've revised this patch slightly,
as shown below. Use "== reverse" instead of "!= forward".

Makes it do the right thing in the "unknown" case.

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2008-09-15 Michael Snyder <msnyder@vmware.com>

* infrun.c (proceed): No need to singlestep over a breakpoint
when resuming in reverse.

Index: infrun.c
===================================================================
RCS file: /cvs/src/src/gdb/infrun.c,v
retrieving revision 1.300.2.5
diff -u -p -r1.300.2.5 infrun.c
--- infrun.c 5 Sep 2008 03:37:10 -0000 1.300.2.5
+++ infrun.c 17 Sep 2008 00:54:00 -0000
@@ -1226,11 +1226,17 @@ 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)
/* There is a breakpoint at the address we will resume at,
step one instruction before inserting breakpoints so that
we do not stop right away (and report a second hit at this
- breakpoint). */
+ breakpoint).
+
+ Note, we don't do this in reverse, because we won't
+ actually be executing the breakpoint insn anyway.
+ We'll be (un-)executing the previous instruction. */
+
oneproc = 1;
else if (gdbarch_single_step_through_delay_p (gdbarch)
&& gdbarch_single_step_through_delay (gdbarch,