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Re: [PATCH] MI: Free values when updating
On Wed, Jan 24, 2007 at 12:02:12AM +1300, Nick Roberts wrote:
> > > it's just that this patch stops calling it at other times
> > > when it's needed. Without any change, do enable timings (if you have that
> > > patch), create a variable object of a large array and all its children then
> > > repeatedly do "-var-update *". It should take longer and longer to execute.
> >
> > Why? Is it because the memory consumption of gdb grows, or because the list
> > of released values grows without ever being cleared, or for some other
> > reason?
>
> The latter, I think.
Except that there isn't a list of released values. So what is GDB
doing that is taking longer and longer?
The call to release_value does a linear walk over all non-released
values. So if we have a lot of things which aren't being released,
then your patch which calls free_all_values is probably the right thing
to do - that should clean it up.
> > - if (gdb_evaluate_expression (var->root->exp, &new_val))
> > - {
> > - release_value (new_val);
> > - }
> > -
> > + gdb_evaluate_expression (var->root->exp, &new_val);
> > return new_val;
> > }
>
> I think if you also remove the (3) calls to release_value in c_value_of_child
> and cplus_value_of_child this is equivalent to my change (and more tidy).
No, those are different. They come from things like the call to
gdb_value_ind in c_describe_child. That creates a new value, which is
returned to the caller (the MI front end, to be printed and later
released). It's the ones in c_value_of_root which matter, because we
save them in the varobj.
You're probably right about the increasing time though - releasing
something already released will be slow. I wonder if we should make
that an internal error somehow.
--
Daniel Jacobowitz
CodeSourcery