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

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C++ named requirements
Basic
Type properties
Library-Wide
Container
Container Elements
CopyInsertable
(C++11)
(C++11)

Iterator
Stream I/O
Formatters
(C++20)
Random Numbers
(C++11)    
Concurrency
(C++11)
(C++11)
Ranges
Other
(C++11)


 

Specifies that an instance of the type can be copy-constructed in-place by a given allocator.

[edit] 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:

  • expr is valid.
  • Evaluating expr does not change the value of v.
  • Right after the evaluation of expr, the value of v is equivalent to *p.

[edit] 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.

[edit] 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 3957 C++11 v could denote an rvalue of type T excluded