Re: [patch 2/2] Do not bpstat_clear_actions on throw_exception #3

[Pedro Alves <pedro at codesourcery dot com>]

On Monday 22 August 2011 15:51:50, Jan Kratochvil wrote:
> On Thu, 18 Aug 2011 18:42:19 +0200, Pedro Alves wrote:
> > Unfortunately, the hook-stop handling is in normal_stop.
> > Your patch clears the breakpoint commands before get get a chance
> > to run if the user installs a hook-stop.  E.g., before:
> 
> OK, I agree, I have made a new testcase.

Thanks.

> > This looks tricky to get right without changing gdb's behavior :-(
> 
> The question is how big changed you were thinking about.
> 
> One problem I find one cannot use "step" and other such commands in the
> breakpoints commands lists.  This may be due to GDB trying not to overflow its
> stack.  I gues with async mode it could be implementable as some
> stack-in-data-structure.

Yes, I going in that direction with
<http://sourceware.org/ml/gdb-patches/2011-06/msg00158.html>,
but there are other places I hadn't made fully state-machined
on that patch.  Unfortunately, I can't afford finishing
that one now, and I flipped to a plan B.

> But that seems to be out of scope of this patch.

For sure.

> > We could try pushing bpstat_do_actions to the end of an execution
> > command's run, but e.g., that would change the behavior of
> > breakpoint commands in command lists, and things like "step N".
> > OTOH, maybe that'd be the right thing to do (the current
> > behavior could be seen as buggy --- more thought is needed).
> 
> I was playing with various changes but it had various side-effects.
> 
> Do you have anything against this patch?  

No, looks almost good enough.  I like that it's simple.

> I hope I have caught all the cases
> where exceptions can be thrown.  Otherwise IMO everything is caught by
> execute_command anyway.

Not all cases.  In async mode, handle_inferior_event is called
_outside_ of execute_command, directly by the event loop (well, almost
directly).  Thus any exception thrown between bpstat_stop_status is called,
and the bpstat_do_actions call in inf-loop.c, will leave the thread
with a dangling bpstat too.  Might be good enough to wrap
handle_inferior_event with a similar cleanup?

-- 
Pedro Alves