std::default_delete

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Memory management library

voidify

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allocator
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Uninitialized memory algorithms

uninitialized_copy
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uninitialized_default_construct (C++17)
uninitialized_value_construct (C++17)
destroy (C++17)
uninitialized_default_construct_n (C++17)
uninitialized_value_construct_n (C++17)
destroy_n (C++17)
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Constrained uninitialized memory algorithms

ranges::uninitialized_copy (C++20)
ranges::uninitialized_fill (C++20)
ranges::uninitialized_move (C++20)
ranges::uninitialized_copy_n (C++20)
ranges::uninitialized_fill_n (C++20)
ranges::uninitialized_move_n (C++20)
ranges::construct_at (C++20)

ranges::uninitialized_default_construct (C++20)
ranges::uninitialized_value_construct (C++20)
ranges::destroy (C++20)
ranges::uninitialized_default_construct_n (C++20)
ranges::uninitialized_value_construct_n (C++20)
ranges::destroy_n (C++20)
ranges::destroy_at (C++20)

Memory resources

pmr::memory_resource (C++17)
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pmr::null_memory_resource (C++17)
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declare_reachable (C++11)(until C++23)
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Low level memory
management

operator newoperator new[]

operator deleteoperator delete[]

(C++11)

(C++11)

(C++17)

(C++20)

(C++17)

(C++11)

(C++11)

(C++11)

(until C++17*)

(C++11)

(C++17)

(C++26)

(C++26)

enable_shared_from_this

(C++11)

bad_weak_ptr

(C++11)

default_delete

(C++11)

(C++23)

(C++23)

(C++11)

(C++20)

(C++11)

(C++11)

(C++20)

is_sufficiently_aligned

(C++26)

C Library

malloc
calloc
realloc

free
aligned_alloc (C++17)

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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 bystd::unique_ptr when no deleter is specified. Specializations ofdefault_delete are empty classes on typical implementations, and used in theempty base class optimization.

1) The non-specializeddefault_delete usesdelete to deallocate memory for a single object.

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

[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()noexcept=default;	(1)
Primary template specializations
template<class U> default_delete(const default_delete<U>& d)noexcept;	(2)	(since C++11) (constexpr since C++23)
Array specializations
template<class U> default_delete(const default_delete<U[]>& d)noexcept;	(3)	(since C++11) (constexpr since C++23)

1) Constructs astd::default_delete object.

2) Constructs astd::default_delete<T> object from anotherstd::default_delete object.

This overload participates in overload resolution only ifU* is implicitly convertible toT*.

3) Constructs astd::default_delete<T[]> object from anotherstd::default_delete<U[]> object.

This overload participates in overload resolution only ifU(*)[] is implicitly convertible toT(*)[].

Parameters

a deleter to copy from

Notes

Theconverting constructor template ofstd::default_delete makes possible the implicit conversion fromstd::unique_ptr<Derived> tostd::unique_ptr<Base>.

std::default_delete::operator()

Primary template specializations
void operator()( T* ptr)const;	(1)	(since C++11) (constexpr since C++23)
Array specializations
template<class U> void operator()( U* ptr)const;	(2)	(since C++11) (constexpr since C++23)

1) Callsdelete onptr.

2) Callsdelete[] onptr.

This overload participates in overload resolution only ifU(*)[] is implicitly convertible toT(*)[].

IfU is an incomplete type, the program is ill-formed.

Parameters

ptr

an object or array to delete

Exceptions

No exception guarantees.

[edit]Invoking over Incomplete Types

At the point in the code theoperator() is called, the type must be complete. In some implementations astatic_assert is used to make sure this is the case. The reason for this requirement is that callingdelete 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.

[edit]Notes

Feature-test macro	Value	Std	Feature
`__cpp_lib_constexpr_memory`	`202202L`	(C++23)	constexpr constructor andoperator()

[edit]Example

Run this code

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