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size of an empty class
Joined: 04 Jan 2005
Posts: 2
size of an empty class
hi all,
can anybody tell the reason
class myclass
{};
void main()
{
cout<<sizeof(myclass);
}
this program prints the size of class as 1 byte. can anybody tell me in details
why it keeps 1 bytes in memory., althouth the class is empty.
also do tell me what happens when we add member functions to this class.
Regards,
===========================
Sudhir Kesharwani
Mob : +91 9822511209
sudhir.kesharwani@...
===========================
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Joined: 02 Jan 2005
Posts: 9
size of an empty class
--- Sudhir Kesharwani <sudhir.kesharwani@...>
wrote:
>
> hi all,
> can anybody tell the reason
> class myclass
> {};
> void main()
> {
> cout<<sizeof(myclass);
> }
>
> this program prints the size of class as 1 byte.
> can anybody tell me in details why it keeps 1 bytes
> in memory., althouth the class is empty.
>
> also do tell me what happens when we add member
> functions to this class.
>
> Regards,
> ===========================
> Sudhir Kesharwani
> Mob : +91 9822511209
> sudhir.kesharwani@...
> ===========================
Hi sudhir,
The size of a class can never be 0 bytes. If it does
not contain any members, the compiler allocates 1 byte
for the class automatically as the class if defined is
a visible entity.
This does not mean that compiler always adds 1 byte to
the overall size of the class. It removes this byte as
soon as you add the first member to the class.
Regards
manik
>
> --
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> Find what you are looking for with the Lycos Yellow
> Pages
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Joined: 29 Dec 2004
Posts: 31
size of an empty class
From: Sudhir Kesharwani [mailto:sudhir.kesharwani@...]
>hi all,
>can anybody tell the reason
>class myclass
>{};
>void main()
>{
>cout<<sizeof(myclass);
>}
>
>this program prints the size of class as 1 byte. can anybody
>tell me in details why it keeps 1 bytes in memory., althouth
>the class is empty.
It`s required by the standard. Two distinct objects *must* be distinct
(i.e. have different addresses), and the way to ensure this is to
require that classes must be at least one byte in size. (Think, e.g., of
an array of such objects)
>also do tell me what happens when we add member functions to
>this class.
The `phantom` byte disappears since there is now something in there that
takes up memory.
--
PJH
"Consistently separating words by spaces became a general custom about
the tenth century A.D., and lasted until about 1957, when FORTRAN
abandoned the practice." -- Sun FORTRAN Reference Manual
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