Memory layout of class

[Peskov Dmitry]

Hi,
What is the memory layout of an object, and the derived object.
For example :

class A
{
private:
int prv_data;
protected:
int pro_data;
public:
int pub_data;
A(){prv_data = 10;}
void Aprint();
};

class B : public A
{
int pro_data;
public:
void Bmember1();
void Bprint();
};

Does it depend on the compiler ?

int main()
{
B b;
int *ptr;

ptr = (int *)&b;
*ptr = 1000;
ptr++;
*ptr = 2000;
ptr++;
*ptr = 3000;
ptr++;
*ptr = 4000;

return 0;
}

is setting only the private element of class A to 1000, rest are not
being set.

[Tarique]

Peskov Dmitry wrote:

Hi,
What is the memory layout of an object, and the derived object.
For example :

class A
{
private:
int prv_data;
protected:
int pro_data;
public:
int pub_data;
A(){prv_data = 10;}
void Aprint();
};

class B : public A
{
int pro_data;
public:
void Bmember1();
void Bprint();
};

Does it depend on the compiler ?

int main()
{
B b;
int *ptr;

ptr = (int *)&b;
*ptr = 1000;
ptr++;
*ptr = 2000;
ptr++;
*ptr = 3000;
ptr++;
*ptr = 4000;

return 0;
}

is setting only the private element of class A to 1000, rest are not
being set.

See
http://www.research.att.com/~bs/bs_faq2.html#layout-obj

[EventHelix.com]

On Jun 29, 1:52*pm, Peskov Dmitry <[e-mail]:

Hi,
* What is the memory layout of an object, and the derived object.
For example :

class A
{
* *private:
* * * * int prv_data;
* *protected:
* * * * int pro_data;
* *public:
* * * * int pub_data;
* * * * A(){prv_data = 10;}
* * * * void Aprint();

};

class B : public A
{
* * int pro_data;
* * public:
* * * * void Bmember1();
* * * * void Bprint();

};

Does it depend on the compiler ?

int main()
{
* * * * B b;
* * * * int *ptr;

* * * * ptr = (int *)&b;
* * * * *ptr = 1000;
* * * * ptr++;
* * * * *ptr = 2000;
* * * * ptr++;
* * * * *ptr = 3000;
* * * * ptr++;
* * * * *ptr = 4000;

* * * * return 0;

}

is setting only the private element of class A to 1000, rest are not
being set.

The memory layout of a class is compiler dependent. The following
article should help:

http://www.eventhelix.com/realtimema...erformance.htm

Memory layout for inherited classes is explained in:

http://www.eventhelix.com/realtimema...formance2..htm

--
http://www.EventHelix.com/EventStudio
Sequence diagram based systems engineering tool

[Jerry Coffin]

In article <2f35231f-96fc-406a-a078-d77fbb1799d6
@i18g2000prn.googlegroups.com>, va**********@gmail.com says...

Hi,
What is the memory layout of an object, and the derived object.

[ ... ]

Does it depend on the compiler ?

Partly. If there's no private/public/protected label between them, items
in an object are required to be placed at increasing addresses. When
there is an intervening private/protected/public label, there is no
guarantee about relative ordering from the standard.

As far as base classes go, IF you're dealing with single inheritance
quite a few compilers put the base class at the beginning of the derived
class. This makes it trivial to convert an object to its base class
object (i.e. the same address, treated as a pointer to the base class,
works). Obviously when you have multiple inheritance, the compiler can
only place one base class at the beginning of the derived class objects.

--
Later,
Jerry.

The universe is a figment of its own imagination.