Trouble switching from vector of dumb pointers to boost::shared_ptr

Question

Alright, this has had me stumped on and off for a couple of months now, so I'll see if anyone else can help with this.

So in my main program I have two kinds of structs (solarBody_t, ship_t) that are both derived from the same base class (physical_t). I make a vector of both objects, since I can't put a solarBody and a ship in the same vector. They are both dumb pointer vectors.
I tried putting both in the same vector, using a vector of boost::shared_ptrs. Now, to my understanding, shared_ptrs should have the same semantics and syntax as dumb pointers (e.g. foobar->mass = 42; should work for both). However, just changing the declaration to a vector of boost::shared_ptr to dumb pointers, it gives me an error when I try and push_back something to the vector of shared_ptrs.

From what I can tell, this should work. The boost docs give the example of

boost::shared_ptr<int> p(new int(2));

which is pretty much what I'm doing.

Has anyone had previous experiences with this? Or want to suggest another way to store everything in a vector?

For more details, here's the gist of it (kind of a contradiction of terms, but I made the pun, so there.)

Answer 1

I don't think it'll let you automatically construct a shared_ptr from a bare pointer. push_back is expecting a shared_ptr<foobar_t>, not a bare foobar_t. You should take a look at boost::make_shared and try something like this:

entity_smart.push_back(boost::make_shared<foobar_t>(42));

make_shared has a few advantages: namely, it allocates the pointer control block and the object itself in one allocation and keeps an unmatched new out of your code. It also makes it explicitly clear that you're creating a shared_ptr to an object.

Other than that, yes, the semantics should be basically the same. Keep in mind that shared_ptr may be overkill for what you're doing, though, if you don't actually need to share ownership of the objects.