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.
| (constructor) | constructs a default_delete object (public member function) |
| operator() | deletes the object or array (public member function) |
constexpr default_delete() noexcept = default; | (1) | |
template <class U> default_delete( const default_delete<U>& d ) noexcept; | (2) | (member only of primary default_delete template) |
template<class U> default_delete( const default_delete<U[]>& d) noexcept; | (3) | (since C++17) (member only of the array default_delete specialization) |
std::default_delete object.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*.std::default_delete<U[]> object from another std::default_delete<U[]> object. This constructor will only participate in overload resolution if U(*)[] is implicitly convertible to T(*)[].| d | - | a deleter to copy from |
The converting constructor template of std::default_delete makes possible the implicit conversion from std::unique_ptr<Derived> to std::unique_ptr<Base>.
void operator()(T* ptr) const; | (1) | (as of C++17, no longer a member of the default_delete<T[]> template specialization) |
template <class U> void operator()(U* ptr) const; | (2) | (member only of default_delete<T[]> template specialization, but defined as deleted prior to C++17) |
1) Calls delete (primary template) or delete[] (array specialization) on ptr 2) Defined as deleted | (until C++17) |
1) Calls delete on ptr 2) Calls delete[] on ptr. This function will only participate in overload resolution if U(*)[] is implicitly convertible to T(*)[]. | (since C++17) |
In any case, if U is an incomplete type, the program is ill-formed.
| ptr | - | an object or array to delete |
No exception guarantees.
At the point in the code the operator() is called, the type must be complete. In some implementations a static_assert is used to make sure this is the case. The reason for this requirement is that calling delete on an incomplete type is undefined behavior in C++ if the complete class type has a nontrivial destructor or a deallocation function, as the compiler has no way of knowing whether such functions exist and must be invoked.
#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>());
}|
(C++11) | smart pointer with unique object ownership semantics (class template) |
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