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This article introduces the relevant knowledge of "how to use the Clear11 Smart pointer shared_ptr". In the operation of actual cases, many people will encounter such a dilemma, so let the editor lead you to learn how to deal with these situations. I hope you can read it carefully and be able to achieve something!

Shared_prt itself is a class, so its initialization is actually a call to the constructor of the shared_ptr class. By analyzing the constructor of shared_ptr, we can accurately grasp the initialization method of shared_ptr.

Default constructor

Function prototype:

Constexpr shared_ptr () noexcept

Description:

Declare an empty shared_ptr.

Code example:

Constructed from null pointers

Function prototype:

Constexpr shared_ptr (nullptr_t)

Description:

The shared_ptr is constructed with a null pointer, and the action default constructor acts the same.

Code example:

Constructed by pointers

Function prototype:

Explicit shared_ptr (U* p)

Description:

Construct shared_ptr based on existing pointers.

Code example:

Matters needing attention

Both of the methods shown in the example are legal, but in the second case it should be understood that once the share_ptr is constructed, it indicates that the memory management of the string object pointed to by s has been handed over to ps1 management and should no longer be accessed through s (at least very carefully).

The second way should be avoided as much as possible.

Copy construction

Function prototype:

Shared_ptr (const shared_ptr& x) noexcept

Description:

Create a new shared_ptr from an existing share_ptr. In the meantime, application counts are automatically maintained.

Code example:

Program output:

After the copy constructor is executed, the reference count increases and two pointers point to the same object.

Mobile structure

Function prototype:

Shared_ptr (shared_ptr&& x) noexcept

Description:

Create a new shared_ptr from an existing share_ptr. Shared_pt, as a parameter, also releases administrative rights to memory, and the reference count remains unchanged after the entire construction process.

Code example:

Program output:

Memory management has been transferred from ps to ps1.

Modifier description

Explicit: ensures that the constructor will not be called implicitly

Noexcept: this function does not throw an exception

Constexpr: this function can be evaluated during compilation

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