Namespaces
Variants
Views
Actions

std::default_delete

From cppreference.com
< cpp‎ | memory
 
 
 
 
std::default_delete
 
Defined in header <memory>
template< class T > struct default_delete
(1) (since C++11)
template< class T > struct default_delete<T[]>
(2) (since C++11)

std::default_delete is the default destruction policy used by std::unique_ptr when no deleter is specified.

1) The non-specialized default_delete uses delete to deallocate memory for a single object.

2) A partial specialization for array types that uses delete[] is also provided.

Contents

[edit] Member functions

(constructor)
constructs a default_delete object
(public member function) [edit]
operator()
deletes the object or array
(public member function) [edit]

std::default_delete::default_delete

constexpr default_delete() = default;
(1) (since C++11)
template <class U>
default_delete( const default_delete<U>& d );
(2) (since C++11)
(member only of generic default_delete template)
1) Constructs a std::default_delete object.
2) Constructs a std::default_delete object from another std::default_delete object. This constructor will only participate in overload resolution if U* is implicitly convertible to T*.

Parameters

d - a deleter to copy from

Exceptions

noexcept specification:  
noexcept
  

Notes

The converting constructor template of std::default_delete makes possible the implicit conversion from std::unique_ptr<Derived> to std::unique_ptr<Base>.

std::default_delete::operator()

void operator()(T* ptr) const;
(1) (since C++11)
template <class U>
void operator()(U* ptr) const = delete;
(2) (since C++11)
(member only of default_delete<T[]> template specialization)

Calls either delete or delete[] on ptr.

Parameters

ptr - an object or array to delete

Exceptions

No exception guarantees.

[edit] Example

#include <memory>
#include <vector>
#include <algorithm>
 
int main()
{
//    {
//        std::shared_ptr<int> shared_bad(new int[10]);
//    } // the destructor calls delete, undefined behavior
 
    {
        std::shared_ptr<int> shared_good(new int[10], std::default_delete<int[]>
());
    } // the destructor calls delete[], ok
 
    {
        std::unique_ptr<int> ptr(new int(5));
    } // unique_ptr<int> uses default_delete<int>
 
    {
        std::unique_ptr<int[]> ptr(new int[10]);
    } // unique_ptr<int[]> uses default_delete<int[]>
 
   // default_delete can be used anywhere a delete functor is needed
   std::vector<int*> v;
   for(int n = 0; n < 100; ++n)
      v.push_back(new int(n));
   std::for_each(v.begin(), v.end(), std::default_delete<int>());
}


[edit] See also

smart pointer with unique object ownership semantics
(class template) [edit]