On Friday, January 30, 2015 at 10:39:12 PM UTC+5:30, Michael Torrie wrote:
> On 01/30/2015 09:27 AM, Rustom Mody wrote:
> > ... if I restate that in other words it says that sufficiently
> > complex data structures will be beyond the reach of the standard
> > RAII infrastructure.
> >
> > Of course this only brings up one side of memory-mgmt problems
> > viz. unreclaimable memory.
> >
> > What about dangling pointers?
> > C++ apps are prone to segfault. Seems to suggest
> > (to me at least) that the memory-management infrastructure
> > is not right.
> >
> > Stroustrup talks of the fact that C++ is suitable for lightweight
> > abstractions. In view of the segfault-proneness I'd say they
> > are rather leaky abstractions.
> >
> > But as I said at the outset I dont understand C++
>
> Yes I can tell you haven't used C++. Compared to C, I've always found
> memory management in C++ to be quite a lot easier. The main reason is
> that C++ guarantees objects will be destroyed when going out of scope.
I hear you and I trust you as a gentleman but I dont trust C++ :-)
The only time in some near 15 years of python use that
I got it to segfault was when Ranting Rick gave some wx code to try
[at that time he was in rant-against-tk mode]
Sure enough it was related to the fact that wx is written in C++
and some expectations were not being followed.
> So when designing a class, you put any allocation routines in the
> constructor, and put deallocation routines in the destructor. And it
> just works. This is something I miss in other languages, even Python.
>
> And for many things, though it's not quite as efficient, when dealing
> with objects you can forgo pointers altogether and just use copy
> constructors, instead of the
>
> blah *a = new blah_with_label("hello") //allocate on heap
> //forget to "delete a" and it leaks the heap *and* anything
> //that class blah allocated on construction.
>
> just simply declare objects directly and use them:
>
> blah a("hello") //assuming there's a constructor that takes a string
> //deletes everything when it goes out of scope
>
> So for the lightweight abstractions Stroustrup talks about, this works
> very well. And you'll rarely have a memory leak (only in the class
> itself) and no "dangling pointers."
And what about the grey area between lightweight and heavyweight?
You say just use copy constructors and no pointers.
Can you (ie C++) guarantee that no pointer is ever copied out of
scope of these copy-constructed objects?
>
> For other things, though, you have to dynamically create objects. But
> the C++ reference-counting smart pointers offer much of the same
> destruction semantics as using static objects. It's really a slick
> system. Almost makes memory management a non-issue. Circular
> references will still leak (just like they do on Python). But it
> certainly makes life a lot more pleasant than in C from a memory
> management perspective.
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