# std::pmr::polymorphic_allocator<T>::allocate

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< cpp‎ | memory‎ | polymorphic allocator

T* allocate( std::size_t n ); |  | (since C++17) (until C++20)
[[nodiscard]] T* allocate( std::size_t n ); |  | (since C++20)

Allocates storage for n objects of type `T` using the underlying memory resource. Equivalent to return static_cast<T*>(resource()->allocate(n * sizeof(T), alignof(T)));.

### Parameters

n | - | the number of objects to allocate storage for

### Return value

A pointer to the allocated storage.

### Exceptions

Throws std::bad_array_new_length if n > std::numeric_limits<std::size_t>::max() / sizeof(T); may also throw any exceptions thrown by the call to resource()->allocate.

### 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 3038 | C++17 | `allocate` might allocate storage of wrong size | throws `length_error` instead
LWG 3237 | C++17 | the exception thrown by `allocate` was inconsistent with `std::allocator::allocate` | made consistent

### See also

allocate_bytes (C++20) | allocate raw aligned memory from the underlying resource (public member function)
allocate_object (C++20) | allocates raw memory suitable for an object or an array (public member function)
new_object (C++20) | allocates and constructs an object (public member function)
allocate [static] | allocates uninitialized storage using the allocator (public static member function of `std::allocator_traits<Alloc>`)
allocate | allocates memory (public member function of `std::pmr::memory_resource`)

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