C + + POD type

Original link: http://blog.csdn.net/bichenggui/article/details/4719363

A simple collation of the main content:

The first to see the type of pod (plain old data) is in imperfect C + +. I think this is a very important book that takes me to C + + world.

This explains the pod in this book:

1, all scalar types (basic type and pointer type), POD structure type, pod union type, and these types of arrays, const/volatile decorated version

This is all pod type.

2, POD structure/union type: An aggregation (including Class), its non-static members are not pointer to class member,

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

volatile modified version;

Also, this aggregation cannot have user-defined constructors, destructors, and copy constructors.

3. Pod types can have static members, member TypeDef, nested STRUCT/CLASS definitions, and member functions/methods.

(c + + standard) the definition given:

Copies the bytes of an object into a byte array, and then copies it back into the storage area of the original object, at which point the object should have its original value.

Characteristics of POD types:

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

Pod Feature utilization:

We can use the pod type attribute 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 the type T is a non pod type, the compiler will make an error, because T is a member of the Union.

The test code in VS2008 is as follows:

Class A

{

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 will complain: 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 nature of pod is a data type compatible with C.