How does C++ realize the intelligent pointer outside the standard library?
This article mainly explains "how C++ can achieve smart pointers outside the standard library". Interested friends may wish to have a look. The method introduced in this paper is simple, fast and practical. Next, let the editor take you to learn how C++ can achieve smart pointers outside the standard library.
R.31: if you need to implement smart pointers other than the standard library, follow the basic pattern in the standard library
Reason (reason)
The guidelines in later chapters also apply to other types of third-party and custom smart pointers, which are effective in finding general smart pointer errors that can cause performance and correctness problems. What you need is a rule that works for all smart pointers.
Any type that overloads unary * and-> (including major templates and specializations) can be considered a smart pointer.
If it is copiable, it is considered a shared pointer with a reference count.
If it is not copiable, it is considered an exclusive unique_ptr.
Example (sample)
/ / use Boost's intrusive_ptr
# include
Void f (boost::intrusive_ptr p) / / error under rule 'sharedptrparam'
{
P-> foo ()
}
/ / use Microsoft's CComPtr
# include
Void f (CComPtr p) / / error under rule 'sharedptrparam'
{
P-> foo ()
}
In both cases, a mistake was made in the sharedptrParam guidelines: P is a shared pointer, but nothing about sharing is used here. And passing smart pointers by value is a default permission; this function should accept smart pointers only when participating in the lifecycle management of widget. Other cases: if functions are allowed to be null, they should accept widget*, otherwise they should accept widget&. These smart pointers match the concept of Shared_pointer, so the rules recommended by these guidelines can also be applied to them immediately.
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