Re: [RFC/Patch] Call overloaded operators to perform valid Python operations on struct/class values.

[Doug Evans <xdje42@gmail.com>]

On Mon, Dec 16, 2013 at 2:24 PM, Siva Chandra <sivachandra@google.com> wrote:
> On Sun, Dec 15, 2013 at 11:48 PM, Doug Evans <xdje42@gmail.com> wrote:
>> For myself, I'm just going slow on this one.  E.g., is there another
>> way to provide this?
>> E.g., some kind of facility that uses gdb's language parsers but let's
>> one pass in gdb.Value objects from Python?
>> It sounds doable, but I haven't thought about it very hard (it might
>> not even make sense, or it may require more effort).
>> Its drawback to the current proposal is that it would be a bit more
>> verbose, but it has to potential of handling a lot more cases.
>
> I am not sure I fully understand this alternative.

It could be done in various ways I think.  One way would be language parsers
and the evaluator have some way of recognizing a value as coming from
an extension language and fetch the underlying gdb value accordingly.
Kinda like the gdb.parse_and_eval method in Python, but with the
ability to pass Python values to it.

Not that this could work, but for illustration's sake:
smart_ptr = gdb.parse_and_eval ("my_smart_ptr");
dereferenced_smart_ptr = gdb.parse_and_eval("*%V" % smart_ptr)

I can think of a quick hack that was just a wrapper on parse_and_eval that
used some convenience variables to temporarily hold the values that
came from Python (using some syntax that worked, the above
is just for illustration's sake).

> My patch adds the
> ability to use valid Python operators on gdb.Value objects in Python
> code.  Operators which have different semantics in Python (like '[]',
> ',' etc.), and operators which do not exist in Python (like '->')
> cannot be facilitated.  But, my patch adds the ability to use all
> other operators which are valid (as far as my understanding today
> stands at) in Python.