std::allocator_traits<Alloc>::allocate
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< cpp | memory | allocator traits
| Defined in header <memory>
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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 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 well-defined according to a strict reading of 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.
Example
| This section is incomplete Reason: no example |
See also
| allocates uninitialized storage (public member function of std::allocator<T>) |