std::allocator_arg (3) - Linux Manuals

std::allocator_arg: std::allocator_arg

NAME

std::allocator_arg - std::allocator_arg

Synopsis

Defined in header <memory>
constexpr std::allocator_arg_t allocator_arg = std::allocator_arg_t(); (since C++11)
                                                                               (until C++17)
inline constexpr std::allocator_arg_t allocator_arg = std::allocator_arg_t(); (since C++17)

std::allocator_arg is a constant of type std::allocator_arg_t used to disambiguate, at call site, the overloads of the constructors and member functions of allocator-aware objects, such as std::tuple,
std::function, std::packaged_task,
(until C++17)and std::promise.