Shulou(Shulou.com)06/01 Report--

This article mainly introduces "why C++ should maintain the consistency of the default operation". In daily operation, I believe many people have doubts about why C++ should maintain the consistency of the default operation. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful to answer the question of "why C++ should maintain the consistency of the default operation". Next, please follow the editor to study!

C.22: keep the default operation consistent

Reason (reason)

The default operation is conceptually a tightly coordinated set of processing. Their semantics are interrelated. Users will be surprised if copy / move constructions and copy / move assignments do logically different things; users will be surprised if constructors and destructors do not provide a consistent idea for resource management; users will be surprised if copy and move operations do not correspond to constructors and destructors.

Example, bad (negative example)

Class Silly {/ / BAD: Inconsistent copy operations

Class Impl {

/ /...

}

Shared_ptr p

Public:

Silly (const Silly& a): P {a.p} {* p = * a.p;} / / deep copy

Silly& operator= (const Silly& a) {p = a.p;} / / shallow copy

/ /...

}

These operations (copy construction and assignment) have different semantics about the copy (deep copy and shallow copy). This can lead to confusion and mistakes.

Enforcement (implementation recommendations)

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