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std::indirect

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< cpp‎ | memory
 
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Memory management library
(exposition only*)
Allocators
Uninitialized memory algorithms
Constrained uninitialized memory algorithms
Memory resources
Uninitialized storage (until C++20)
(until C++20*)
(until C++20*)
(until C++20*)

Garbage collector support (until C++23)
(C++11)(until C++23)
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std::indirect
 
Defined in header <memory>
template< class T, class Allocator = std::allocator<T> >
class indirect;
 (1) (since C++26)
namespace pmr {

    template< class T >
    using indirect = std::indirect<T, std::pmr::polymorphic_allocator<T>>;

}
 (2) (since C++26)
1) std::indirect is a wrapper containing dynamically-allocated object with value-like semantics.
2) std::pmr::indirect is an alias template that uses a polymorphic allocator.

An std::indirect object manages the lifetime of an owned object. An std::indirect object can only have no owned object after it has been moved from, in this case it is valueless .

Every object of type std::indirect<T, Allocator> uses an object of type Allocator to allocate and free storage for the owned object as needed.

If a program declares an explicit or partial specialization of std::indirect, the behavior is undefined.

Contents

[edit] Template parameters

T - the type of the owned object
Allocator - the type of the associated allocator
Type requirements
-
T may be an incomplete type.
-
If T is one of the following types, the program is ill-formed:
-
If Allocator does not satisfy the requirements of Allocator, the program is ill-formed.
-
If std::allocator_traits<Allocator>::value_type is not the same type as T, the program is ill-formed.

[edit] Nested types

Type Definition
value_type T
allocator_type Allocator
pointer typename std::allocator_traits<Allocator>::pointer
const_pointer typename std::allocator_traits<Allocator>::const_pointer

[edit] Data members

Member Description
pointer p a pointer to the owned value
(exposition-only member object*)
Allocator alloc the asociated allocator
(exposition-only member object*)

[edit] Member functions

 constructs the indirect object
(public member function) [edit]
destroys the owned value, if there is one
(public member function) [edit]
assigns contents
(public member function) [edit]
Observers
accesses the owned value
(public member function) [edit]
checks if the indirect is valueless
(public member function) [edit]
returns the associated allocator
(public member function) [edit]
Modifiers
exchanges the contents
(public member function) [edit]

[edit] Non-member functions

(C++26)(C++26)
 compares indirect objects
(function template) [edit]
(C++26)
 specializes the std::swap algorithm
(function template) [edit]

[edit] Helper classes

(C++26)
 hash support for std::indirect
(class template specialization) [edit]

[edit] Deduction guides

[edit] Notes

Feature-test macro Value Std Feature
__cpp_lib_indirect 202502L (C++26) std::indirect

[edit] Example

This section is incomplete
Reason: no example

[edit] See also

(C++26)
 a polymorphic wrapper containing dynamically-allocated object with value-like semantics
(class template) [edit]
(C++11)
 smart pointer with unique object ownership semantics
(class template) [edit]
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