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std::allocator_traits::allocate(3) | C++ Standard Libary | std::allocator_traits::allocate(3) |
NAME¶
std::allocator_traits::allocate - std::allocator_traits::allocate
Synopsis¶
Defined in header <memory>
static pointer allocate( Alloc& a, size_type n (since C++11)
); (until C++20)
[[nodiscard]] static constexpr pointer allocate( (since C++20)
Alloc& a, size_type n );
static pointer allocate( Alloc& a, size_type n, (1) (since
C++11)
const_void_pointer hint ); (until C++20)
[[nodiscard]] static constexpr pointer allocate( (2)
Alloc& a, size_type n, (since C++20)
const_void_pointer hint );
Uses the allocator a to allocate n*sizeof(Alloc::value_type) bytes of
uninitialized
storage. An array of type Alloc::value_type[n] is created in the storage, but
none
of its elements are constructed.
1) Calls a.allocate(n)
2) Additionally passes memory locality hint hint. Calls a.allocate(n, hint)
if
possible. If not possible (e.g. a has no two-argument member function
allocate()),
calls a.allocate(n)
Parameters¶
a - allocator to use
n - the number of objects to allocate storage for
hint - pointer to a nearby memory location
Return value¶
The pointer returned by the call to a.allocate(n)
Notes¶
Alloc::allocate was not required to create array object until
P0593R6, which made
using non-default allocator for std::vector and some other containers not
actually
well-defined according to the core language specification.
After calling allocate and before construction of elements, pointer
arithmetic of
Alloc::value_type* is well-defined within the allocated array, but the
behavior is
undefined if elements are accessed.
See also¶
allocate allocates uninitialized storage
(public member function of std::allocator<T>)
2022.07.31 | http://cppreference.com |