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

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: 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*
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:

• T is MoveInsertable into X .
• expr is well-formed.
• Evaluating expr does not change the value of v .
• Right after the evaluation of expr , the value of v is 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