C++ named requirements: CopyInsertable (since C++11)
From cppreference.com
Specifies that an object of the type can be copy-constructed in-place 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:
|
| Value | Definition |
m
|
an lvalue of type A
|
p
|
a pointer of type T*
|
| Expression | Definition |
v
|
an expression denoting an lvalue of type T / const T, or an rvalue of type const T
|
expr
|
std::allocator_traits<A>::construct(m, p, v)
|
T is CopyInsertable into X if all following conditions are satisfied:
Tis MoveInsertable intoX.expris well-formed.- Evaluating
exprdoes not change the value ofv. - Right after the evaluation of
expr, the value ofvis equivalent to*p.
Notes
If A is std::allocator<T>, then this will call placement new, as by ::new((void*)p) T(v)(until C++20)std::construct_at(p, v)(since C++20).
Although it is required that customized construct is used when constructing 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 |
|---|---|---|---|
| LWG 2177 | C++11 | evaluting expr did not have any postcondition
|
added |
| LWG 3957 | C++11 | v could denote an rvalue of type T
|
excluded |