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Re: MI non-stop mode spec


On Sunday 23 March 2008 07:40:17 Nick Roberts wrote:
> ?> > ?> > ?> Didn't you check in a patch to make *-varobjs be found to a
> ?> > ?> > ?> thread?
> ?> > ?> >
> ?> > ?> > I submitted a patch earlier this year that stopped thinking that
> ?> > ?> > a variable object had gone out of scope if the thread changed
> ?> > ?> > but nothing happened.
> ?> > ?>
> ?> > ?> Can you resend the current version of that patch, and I'll take a
> ?> > ?> look.
> ?> >
> ?> > I used pid_to_thread_id (inferior_ptid) for the thread_id, just as
> ?> > infrun.c does for *stopped. ?I think that the thread_id problem for
> ?> > single/multi-threaded programs should be fixed first (perhaps along
> ?> > the lines Daniel suggested).
> ?> 
> ?> Dan's patch is in, however, it only affects Linux. I suspect in might
> ?> be a long time till the problem is solved on all system. Until then,
> ?> we probably should assume that if thread list is empty, then the 
> ?> program is ST and never will become MT.
> ?> 
> ?> I happen to be working on variable objects for non-stop now, so I'll
> ?> play with the last version of your patch that you have posted.
> 
> I've made some changes since then so here's my latest patch updated to current
> sources. ?I found that after all I did need thread_id == -2 for global
> variables (used in mi-cmd-var which doesn't print the thread_id field for them
> since their value is the same in all threads).

I don't think we need it. A global variable has a NULL valid_block, so we can
use that. I'll work on adjusting your patch this way.

> ? static struct value *
> ? c_value_of_root (struct varobj **var_handle)
> ? {
> ? ? struct value *new_val = NULL;
> ? ? struct varobj *var = *var_handle;
> ! ? struct frame_id saved_frame_id;
> ! ? struct cleanup *old_cleanups = NULL;
> ! ? int within_scope, thread_id;
> ! ? ptid_t ptid;
> ? 
> ? ? /* ?Only root variables can be updated... */
> ? ? if (!is_root_p (var))
> ? ? ? /* Not a root var */
> ? ? ? return NULL;
> ? 
> ? ? /* Determine whether the variable is still around. */
> ? ? if (var->root->valid_block == NULL || var->root->use_selected_frame)
> ? ? ? within_scope = 1;
> ? ? else
> ? ? ? {
> ! ? ? ? thread_id = var->root->thread_id;
> ! ? ? ? ptid = thread_id_to_pid (thread_id);
> ! ? ? ? if (thread_id == 0)
> ! ??????/* Single-threaded application. ?*/
> ! ??????within_scope = check_scope (var);
> ! ? ? ? else if (thread_id != -1 && target_thread_alive (ptid))
> ? ??????{
> ! 
> ! ?????? ?saved_frame_id = get_frame_id (get_selected_frame (NULL));
> ! ?????? ?old_cleanups = make_cleanup_restore_current_thread (inferior_ptid,
> ! ?????????????????????????????????????????????????????? ? ? ?saved_frame_id);
> ! ?????? ?switch_to_thread (ptid);
> ! ?????? ?within_scope = check_scope (var);
> ! ??????}
> ! ? ? ? else
> ! ??????/* Mark it as dead. ?*/
> ! ??????var->root->thread_id = -1;
> ? ? ? }
> ? 
> ? ? if (within_scope)
> *************** c_value_of_root (struct varobj **var_han
> *** 2186,2191 ****
> --- 2233,2240 ----
> ? ? ? ? return new_val;
> ? ? ? }
> ? 
> + ? do_cleanups (old_cleanups);
> + 
> ? ? return NULL;
> ? }

I think the use of cleanups above is wrong. You basically have:

	struct cleanups *old_cleanups = NULL;
	if (whatever)
		old_cleanups = ...
	do_cleanups (old_cleanups);

so, if 'whatever' evaluates to false, all cleanups, including those set
in parent, will be executed.

That's what we get for using a language that does not have exceptions
and proper destructors. I'll fix this too.

- Volodya


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