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

Michael Snyder
2008-09-15T18:33:54Z

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When we're stopped at a breakpoint and we want to
continue in reverse, we're not actually going to
execute the instruction at the breakpoint -- we're
going to de-execute the previous instruction.

Therefore there's no need to singlestep before
inserting breakpoints. In fact it would be a bad
idea to do so, because if there is a breakpoint at
the previous instruction, we WANT to hit it.

Note that this patch is to be applied to the reverse branch.

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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 15 Sep 2008 18:28:29 -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_FORWARD)
/* 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,