TR1 Shared Arrays

Question

I've had a hard time finding references in the TR1 documentation concerning shared arrays. The Boost documentation is fairly clear that there is a significant difference between the C++ "new" and "new[]" expressions. The shared_ptr template is meant to correctly hold a pointer to a dynamically allocated objected created using "new". The shared_array template is meant to correctly hold a pointer to a dynamically allocated array using "new[]".

I'm in the process of updating some code to use the TR1 shared_ptr template and associated functions, but I've found no mention of shared_array. Does the TR1 shared_ptr implementation differentiate between "new" and "new[]", and destroy those pointers correctly? As far as I can tell from looking at the TR1 spec, it appears it does not. If this is the case, should I still be using the boost shared_array template for "new[]" style allocations?

Answer 1

That is correct, there is no shared_array in TR1.

You can, however, provide your own deleter object to perform "delete []" if you wish using this constructor:

template<class Other, class D>
   shared_ptr(Other* ptr, D dtor);

For example:

template<typename T>
struct my_array_deleter
{
   void operator()(T* p)
   {
      delete [] p;
   }
};

shared_ptr<int> sp(new int[100], my_array_deleter<int>());

Answer 2

I suspect that most people who use TR1 do not use arrays, but use vector<> instead.

I haven't read TR1, so I'll answer on the basis of Boost, which is probably good enough. boost::shared_ptr<> deals with individual objects, and not arrays. That's what boost::shared_array<> is for.

If you're using arrays, and have reasons to convert to shared_array<> but not to vector<>, use shared_array<>.