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Re: Regression
On Tuesday 10 February 2009 18:39:04, Mark Kettenis wrote:
> I've looked at the PR mentioned in the commi message, and I don't
> quite understand how the change to the signal command has anything to
> do with that.
Before Daniel's Daniel's patch, `signal_command' called `proceed'
like so:
+ proceed (oursig == TARGET_SIGNAL_0 ? (CORE_ADDR) -1 : stop_pc, oursig, 0);
For a signal != TARGET_SIGNAL_0, say signal FOO, that's effectivelly this:
proceed (stop_pc, oursig, 0);
void
proceed (CORE_ADDR addr, enum target_signal siggnal, int step)
{
(...)
if (addr == (CORE_ADDR) -1)
{
if (pc == stop_pc && breakpoint_here_p (pc)
&& 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).
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,
get_current_frame ()))
/* We stepped onto an instruction that needs to be stepped
again before re-inserting the breakpoint, do so. */
oneproc = 1;
}
else
{
regcache_write_pc (regcache, addr);
}
(...)
This messed with syscall restarting on linux, since it was
writing the PC.
Notice that the (addr != (CORE_ADDR) -1) code path doesn't
set `oneproc', hence, ends up *not* removing
breakpoints, and *not* single-stepping, even if we were stopped
at a breakpoint. That is what I call the "jump" behaviour --- a jump
to $PC hits a breakpoint at $PC.
After Daniel's change, signal_command does this unconditionaly:
proceed ((CORE_ADDR) -1, oursig, 0);
Which means we now go through the "(addr == (CORE_ADDR) -1)"
branch above. This avoided the regcache_write_pc call. But, it also
sets `oneproc' because in this case, there's a breakpoint at
stop_pc, and PC is still at stop_pc. That will make us remove
breakpoints from the inferior, and call `resume' with step=1.
The part that's breakpoint the BSDs is the fact that we now
remove breakpoints from the inferior.
--
Pedro Alves