There can be many reasons. To list few of them:
- Smart pointers became part of standard just recently. Till then they
were part of other libraries
- Their primary use is to avoid memory leaks; many libraries
don't have their own memory management; Generally they provide
utilities and APIs
- They are implemented as wrapper, since they are actually objects and not pointers. Which has additional time/space cost, compared to raw pointers; The users of the libraries may not want to have such overheads
Edit: Using smart pointers is a completely developer's choice. It depends on various factors.
In performance critical systems, you may not want to use smart
pointers which generates overhead
The project which needs the backward compatibility, you may not want
to use the smart pointers which has C++11 specific features
Edit2 There is a string of several downvotes in the span of 24 hours because of below passage. I fail to understand why the answer is downvoted even though below is just an add-on suggestion and not an answer.
However, C++ always facilitates you to have the options open. :) e.g.
template<typename T>
struct Pointer {
#ifdef <Cpp11>
typedef std::unique_ptr<T> type;
#else
typedef T* type;
#endif
};
And in your code use it as:
Pointer<int>::type p;
For those who say that a smart pointer and a raw pointer are different, I agree with that. The code above was just an idea where one can write a code which is interchangeable just with a #define, this is not compulsion;
For example, T* has to be deleted explicitly but a smart pointer does not. We can have a templated Destroy() to handle that.
template<typename T>
void Destroy (T* p)
{
delete p;
}
template<typename T>
void Destroy (std::unique_ptr<T> p)
{
// do nothing
}
and use it as:
Destroy(p);
In the same way, for a raw pointer we can copy it directly and for smart pointer we can use special operation.
Pointer<X>::type p = new X;
Pointer<X>::type p2(Assign(p));
Where Assign() is as:
template<typename T>
T* Assign (T *p)
{
return p;
}
template<typename T>
... Assign (SmartPointer<T> &p)
{
// use move sematics or whateve appropriate
}
