Defined in header <memory> | ||
---|---|---|
template< class T, class Alloc, class... Args > shared_ptr<T> allocate_shared( const Alloc& alloc, Args... args ); | (since C++11) |
Constructs an object of type T
and wraps it in a std::shared_ptr
using args
as the parameter list for the constructor of T
.
All memory allocation is done using a copy of alloc
, which satisfies the Allocator
requirements. The copy constructor and the destructor of Alloc
must not throw exceptions.
Parameters
alloc | - | The Allocator to use. |
args... | - | list of arguments with which an instance of T will be constructed. |
Return value
std::shared_ptr
of an instance of type T
.
Exceptions
Can throw the exceptions thrown from Alloc::allocate()
or from the constructor of T
. If an exception is thrown, this function has no effect.
Notes
This function typically allocates memory for the T object and for the shared_ptr's control block with a single memory allocation (it is a non-binding requirement in the Standard). In contrast, the declaration std::shared_ptr<T> p(new T(Args...))
performs at least two memory allocations, which may incur unnecessary overhead.
A copy of alloc
is stored as part of the control block so that it can be used to deallocate it once both shared and weak reference counts reach zero.
See also
constructs new shared_ptr (public member function) | |
creates a shared pointer that manages a new object (function template) |
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