Re: MI Development

[Vladimir Prus <ghost at cs dot msu dot su>]

On Tuesday 04 September 2007 18:28:15 Andrà PÃnitz wrote:

> > Variable objects and RTTI
> > For C++, variable objects are not able to look at the real type of the object.
> > only the static type is shown. We should be able to implement display of
> > al type, using Apple's branch as reference.
> 
> Personally I think variable objects are not very well suited for C++ at all.
> Say, I want to display a "std::vector<int> x"in a frontend I usually do not
> want to show three pointers to some internal data. Instead I usually want
> to have  x[0]...x[x.size()-1] as children. This is doable with variable objects,
> but the result feels clumsy, and the "update" feature cannot really be
> used.

I think we can fix that. I'd imagine we can make gdb invoke a Python hook
on -var-list-children. That hook will compute values that correspond to vector
member and create variable objects out of those. There's some work on Python
scripting already; I'd hope this use case will be kept in mind.

There's extra problem is that MI is not prepared that the number of children
of a variable objects can change -- and it can change in case of a vector. We'd
need to fix that.
 
> > Variable objects don't care much about C++ scopes. For example, it's not possible to
> > create a variable object for a given expression in particular scope, which makes it impossible
> > to accurately implement variable tooltips. Also, it's not possible to list all local variables in the
> > entire function, which requires extraordinary effort to display all local variables as the enter
> > scope and leave scope.
> 
> Yup. And there seems to be no way to reliably tell whether a (C++) variable has already been
> constructed.

This is indeed big problem, and I don't know if anybody's working on getting gcc to produce
accurate debug information for that.

- Volodya