C ++ pod types

We first saw the pod (plain old data) type in imperfect C ++. I think this is a very important book that has brought me into the C ++ world.

The book explains pod as follows:

 

1. All scalar types (Basic Types and pointer types), POD structure types, POD Union types, arrays of these types, const/volatile modified versions

These are all pod types.

 

2. Pod structure/Joint Type: A combination (including class), its non-static members are not pointer to class member,

Pointer to class member function, non-pod structure, non-pod union, and arrays, references, const/

Version modified by volatile;

In addition, this aggregate cannot have user-defined constructor, destructor, or copy constructor.

 

3. the pod type can include static members, member typedef, nested struct/class definitions, and member functions/methods.

 

(C ++ standard:

Copy each byte of the object to a byte array, and then copy it to the storage area occupied by the original object. At this time, the object should have its original value.

 

Pod type features:

All pod types can be union members. Otherwise, all non-pod types cannot be union members.

Pod features utilization:

We can use the pod Type feature to determine whether a type is a pod type:

Template <class T> struct must_be_pod

{

Union

{

T noname;

};

};

 

This template means that as long as type T is not of the pod type, the compiler will report an error because T is a member of the Union.

The test code in vs2008 is as follows:

 

Class

{

Public:

 

A (){}

Void F () {cout <"A: F" <Endl ;}

Protected:

PRIVATE:

Int I;

Int J;

};

 

 

Template <class T> struct must_be_pod

{

Union

{

T noname;

};

};

 

Must_be_pod <A> A; the compiler reports the following error: 1> member 'must _ be_pod <t >:: noname' of Union 'must _ be_pod <t> :: <unnamed-tag> 'has User-Defined constructor or non-trivial default constructor

 

In fact, the pod is essentially a data type compatible with C.