std::allocator_traits<Alloc>::allocate

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Compiler support
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Language
Standard library
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Feature test macros(C++20)
Language support library
Concepts library(C++20)
Diagnostics library
Memory management library
Metaprogramming library(C++11)
General utilities library
Containers library
Iterators library
Ranges library(C++20)
Algorithms library
Strings library
Text processing library
Numerics library
Date and time library
Input/output library
Filesystem library(C++17)
Concurrency support library(C++11)
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Memory management library

voidify

(exposition only*)

Allocators

allocator
allocator_traits (C++11)
allocation_result (C++23)
scoped_allocator_adaptor (C++11)
pmr::polymorphic_allocator (C++17)

allocator_arg (C++11)
uses_allocator (C++11)
uses_allocator_construction_args (C++20)
make_obj_using_allocator (C++20)
uninitialized_construct_using_allocator (C++20)

Uninitialized memory algorithms

uninitialized_copy
uninitialized_fill
uninitialized_move (C++17)
uninitialized_copy_n (C++11)
uninitialized_fill_n
uninitialized_move_n (C++17)
construct_at (C++20)

uninitialized_default_construct (C++17)
uninitialized_value_construct (C++17)
destroy (C++17)
uninitialized_default_construct_n (C++17)
uninitialized_value_construct_n (C++17)
destroy_n (C++17)
destroy_at (C++17)

Constrained uninitialized memory algorithms

ranges::uninitialized_copy (C++20)
ranges::uninitialized_fill (C++20)
ranges::uninitialized_move (C++20)
ranges::uninitialized_copy_n (C++20)
ranges::uninitialized_fill_n (C++20)
ranges::uninitialized_move_n (C++20)
ranges::construct_at (C++20)

ranges::uninitialized_default_construct (C++20)
ranges::uninitialized_value_construct (C++20)
ranges::destroy (C++20)
ranges::uninitialized_default_construct_n (C++20)
ranges::uninitialized_value_construct_n (C++20)
ranges::destroy_n (C++20)
ranges::destroy_at (C++20)

Memory resources

pmr::memory_resource (C++17)
pmr::get_default_resource (C++17)
pmr::set_default_resource (C++17)
pmr::new_delete_resource (C++17)
pmr::pool_options (C++17)

pmr::null_memory_resource (C++17)
pmr::synchronized_pool_resource (C++17)
pmr::unsynchronized_pool_resource (C++17)
pmr::monotonic_buffer_resource (C++17)

Explicit lifetime management
start_lifetime_as (C++23)
start_lifetime_as_array (C++23)

Types for composite class design
indirect (C++26)
polymorphic (C++26)

Uninitialized storage(until C++20)

raw_storage_iterator (until C++20*)
get_temporary_buffer (until C++20*)

return_temporary_buffer (until C++20*)

Garbage collector support(until C++23)

declare_reachable (C++11)(until C++23)
declare_no_pointers (C++11)(until C++23)
pointer_safety (C++11)(until C++23)

undeclare_reachable (C++11)(until C++23)
undeclare_no_pointers (C++11)(until C++23)
get_pointer_safety (C++11)(until C++23)

Low level memory
management

operator newoperator new[]

operator deleteoperator delete[]

(C++11)

(C++11)

(C++17)

(C++20)

(C++17)

(C++11)

(C++11)

(C++11)

(until C++17*)

(C++11)

(C++17)

(C++26)

(C++26)

enable_shared_from_this

(C++11)

(C++11)

(C++11)

(C++23)

(C++23)

(C++11)

(C++20)

(C++11)

(C++11)

(C++20)

is_sufficiently_aligned

(C++26)

C Library

malloc
calloc
realloc

free
aligned_alloc (C++17)

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std::allocator_traits

Member types
Member functions
allocator_traits::allocate
allocator_traits::allocate_at_least (C++23)
allocator_traits::deallocate
allocator_traits::construct
allocator_traits::destroy
allocator_traits::max_size
allocator_traits::select_on_container_copy_construction

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Defined in header`<memory>`
static pointer allocate( Alloc& a, size_type n);	(1)	(since C++11) (constexpr since C++20)
static pointer allocate( Alloc& a, size_type n, const_void_pointer hint);	(2)	(since C++11) (constexpr since C++20)

Uses the allocatora to allocaten* sizeof(Alloc::value_type) bytes of uninitialized storage. An array of typeAlloc::value_type[n] is created in the storage, but none of its elements are constructed.

1) Callsa.allocate(n).

2) Additionally passes memory locality hinthint. Callsa.allocate(n, hint) if possible. If not possible (e.g.a has no two-argument member functionallocate), callsa.allocate(n).

[edit]Parameters

a	-	allocator to use
n	-	the number of objects to allocate storage for
hint	-	pointer to a nearby memory location

[edit]Return value

The pointer returned by the call toa.allocate(n).

[edit]Notes

Alloc::allocate was not required to create array object untilP0593R6, which made using non-default allocator forstd::vector and some other containers not well-defined according to a strict reading of the core language specification.

After callingallocate and before construction of elements, pointer arithmetic ofAlloc::value_type* is well-defined within the allocated array, but the behavior is undefined if elements are accessed.