C++ named requirements: Erasable (since C++11)

Specifies that an object of the type can be destroyed by a given Allocator .

Requirements

Given the following types, values and expressions:

Type	Definition
T	an object type
A	an allocator type
X	a container type satisfying all following conditions: X::value_type is the same as T . X::allocator_type is the same as std:: allocator_traits < A > :: rebind_alloc < T > .
Value	Definition
m	an lvalue of type A
p	a pointer of type T*

If the expression std:: allocator_traits < A > :: destroy ( m, p ) is well-formed, T is Erasable from X .

Notes

All standard library containers require that their value types satisfy Erasable .

With the default allocator, this requirement is equivalent to the validity of p - > ~T ( ) , which accepts class types with accessible destructors and all scalar types, but rejects array types, function types, reference types, and void .	(until C++20)
With the default allocator, this requirement is equivalent to the validity of std:: destroy_at ( p ) , which accepts class types with accessible destructors and all scalar types, as well as arrays thereof.	(since C++20)

Although it is required that customized destroy is used when destroying elements of std::basic_string until C++23, all implementations only used the default mechanism. The requirement is corrected by P1072R10 to match existing practice.

Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

DR	Applied to	Behavior as published	Correct behavior
N3346	C++11	there was no requirement to specify whether a type whose objects can be destroyed using allocators	added the requirement

See also

CopyInsertable

MoveInsertable

EmplaceConstructible

Destructible