C++ named requirements: Erasable (od C++11)
Specifies that an object of the type can be destroyed by a given Allocator.
The type T is Erasable from the container X whose value_type is identical to T if given
A
an allocator typem
an lvalue of typeA
p
the pointer of typeT*
prepared by the container
where X::allocator_type is identical to std::allocator_traits<A>::rebind_alloc<T>
,
the following expression is well-formed:
std::allocator_traits<A>::destroy(m, p);
If X is not allocator-aware or is a std::basic_string specialization, the term is defined as if A were std::allocator<T> except that no allocator object needs to be created, and user-defined specializations of std::allocator are not instantiated.
Notes
All standard library containers require that their element type satisfies 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. (do 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. (od 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.