Re: [PATCH/RFC] Improve the "thread_step_needed" logic

[Michael Snyder <msnyder@cygnus.com>]

Daniel Jacobowitz wrote:
> 
> On Fri, Jun 15, 2001 at 04:35:09PM -0700, Michael Snyder wrote:
> > This is a fairly significant change, that both simplifies and
> > improves the logic for deciding when a single thread should be
> > stepped (to get past a breakpoint), rather than stepping all threads.
> > In a nutshell, this replaces the state variable "thread_step_needed"
> > with the following logic in resume():
> 
> <sigh>
> 
> While you're fixing this, could you please address my issue from last
> week with this code?  Checking "step" at this point in resume() is not
> correct, since it will have been cleared if SOFTWARE_SINGLE_STEP_P ().
> 
> > --- 879,913 ----
> >     if (should_resume)
> >       {
> >         ptid_t resume_ptid;
> > +
> > +       resume_ptid = RESUME_ALL;             /* Default */
> >
> > !       if ((step || singlestep_breakpoints_inserted_p) &&
> > !       !breakpoints_inserted && breakpoint_here_p (read_pc ()))
> 
> > +
> > + #ifdef CANNOT_STEP_BREAKPOINT
> > +       /* Most targets can step a breakpoint instruction, thus executing it
> > +      normally.  But if this one cannot, just continue and we will hit
> > +      it anyway.  */
> > +       if (step && breakpoints_inserted && breakpoint_here_p (read_pc ()))
> > +     step = 0;
> > + #endif
> 
> Specifically, those bits.

Oh, sorry, I missed this part of your msg.  
Well, this isn't related to SOFTWARE_SINGLESTEP_P, 
it's a separate issue.  But if you'll notice, I believe this is also 
handled correctly, because my "thread_step_needed" test includes
(NOT breakpoints_inserted), while this CANNOT_STEP_BREAKPOINT clause
will only be taken if breakpoints_inserted is true.  So they are
mutually exclusive, if you will.  I tested this on Alpha Linux, which
does NOT use software single step, but DOES use CANNOT_STEP_BREAKPOINT,
and it works.

Michael