where this pointer stored in object of empty class

Question

class does not have any data member but it has some method . in this case the size of object of class is 1 byte.this pointer which is passed with object when member function is invoked . how is it possible object of 1 byte have this pointer - This pointer typically has size of void* and assume it is 4 bytes

This pointer doesn't belong to the Class object. Please refer http://stackoverflow.com/questions/16585562/where-is-the-this-pointer-stored-in-computer-memory for more info. — neo, Sep 22 '15 at 05:46
The `this` pointer is **not** a class member, it is the location in memory where the class object is stored. An external object holds the pointer to the object which is (notionally) assigned to the `this` pointer when the method is invoked. — Galik, Sep 22 '15 at 05:47

score 1 · Answer 1 · edited May 23 '17 at 11:58

1

this doesn't belong to the Class object. this behaves mostly like a function argument. In your question "this pointer which is passed with object when member function is invoked", I would like to point out that this is not passed with object, Object address is passed to the this pointer.

Please refer Where is the 'this' pointer stored in computer memory? for more info on this.

edited May 23 '17 at 11:58

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answered Sep 22 '15 at 06:08

neo

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score 0 · Answer 2 · answered Sep 22 '15 at 05:55

The size of a pointer in C/C++ is always equal to the size of memory address length. (4 bytes)

The size of an class of empty fields is using a separate address. (1 byte)

if we have a class instance of this type, when you count it's size by

sizeof(instance) == 1

but

sizeof(&instance) == 4 (on 32 bits system)

so you can put an address of instance to a pointer like:

void *p = &instance;

here sizeof(p) == 4;

This needs 4 bytes to hold the address/pointer to instance.

score 0 · Answer 3 · answered Sep 22 '15 at 05:57

The this pointer is not a class member, the compiler adds it to the method calls behind the scenes as a hidden parameter.

Consider:

struct Object
{
    void method(int i);
};

The compiler turns that into something like:

void Object::method(Object* this, int i); // note the extra first parameter

When you do:

Object object;
object->method(5);

The compiler does something like:

Object object;
Object::method(&object, 5);

The hidden first parameter is called this.

where this pointer stored in object of empty class

3 Answers3