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

Specifies that an object of the type can be constructed from a given set of arguments in uninitialized storage by a given allocator.


The type T is EmplaceConstructible into the Container X (whose value_type is identical to T) from the arguments args if, given.

A an allocator type
m an lvalue of type A
p the pointer of type T* prepared by the container
args zero or more arguments

where X::allocator_type is identical to std::allocator_traits<A>::rebind_alloc<T>,

the following expression is well-formed:

std::allocator_traits<A>::construct(m, p, args);

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.


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.

See also


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