On Thursday, 8 October 2015 at 12:10:24 UTC, Ola Fosheim Grøstad
wrote:
On Thursday, 8 October 2015 at 11:31:49 UTC, Kagamin wrote:
cyclic graph. If you must manually verify the graph and put
weak references appropriately - what kind of design in that?
It's a system programming language design... If you plan your
model before coding it is rather easy to detect cycles in the
model. Make the primary data structure a directed acyclic
graph, then add back pointers as weak_ptr for secondary
relations.
I've programmed extensively in C++ with smart pointers, and in my
experience, circular references are rarely a problem. There are
some cases where it's obvious that you have one (e.g. where one
object owns another and they need to talk to each other), in
which case you either use a normal pointer or a weak reference,
depending on which makes more sense. And in the cases that you
don't catch, you find them in testing, figure out what should be
a weak reference to get rid of the circular dependency, you fix
it, and you move on. It really isn't a big deal in general,
though I suppose that there could be certain ways of designing
programs where it would be more problematic.
One advantage of using smart pointers with a GC is that the GC
can then clean up circular references, and you don't necessarily
even need weak pointers (though there are bound to be cases where
they'd still be desirable). But the GC isn't required to solve
the problem. It just makes it so that if you do end up with a
circular reference problem, it'll fix itself.
- Jonathan M Davis
