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Specifies that an object of the type can be copy-constructed in-place by a given allocator.
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:
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| Value | Definition |
| m | an lvalue of typeA |
| p | a pointer of typeT* |
| Expression | Definition |
| v | an expression denoting an lvalue of typeT /const T, or an rvalue of typeconst T |
| expr | std::allocator_traits<A>::construct(m, p, v) |
T isCopyInsertable intoX if all following conditions are satisfied:
T isMoveInsertable intoX.IfA isstd::allocator<T>, then this will call placementnew, as by::new((void*)p) T(v)(until C++20)std::construct_at(p, v)(since C++20).
Although it is required that customizedconstruct is used when constructing elements ofstd::basic_string until C++23, all implementations only used the default mechanism. The requirement is corrected byP1072R10 to match existing practice.
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 | evalutingexpr did not have any postcondition | added |
| LWG 3957 | C++11 | v could denote an rvalue of typeT | excluded |
