< cpp‎ | memory
Utilities library
Type support (basic types, RTTI, type traits)
Dynamic memory management
Error handling
Program utilities
Variadic functions
Date and time
Function objects
Relational operators
Optional and any
Pairs and tuples
Swap, forward and move
Type operations
Defined in header <memory>
constexpr std::allocator_arg_t allocator_arg = std::allocator_arg_t();
(since C++11)

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::promise, and std::packaged_task.

[edit] See also

tag type used to select allocator-aware constructor overloads
checks if the specified type supports uses-allocator construction
(class template)