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memory allocated to objects

Posted on 2004-10-13
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hi ,
i heard that if we declare an object like
abc obj;
{assuming abc is a class}
it is allocated stack memory

and when
abc *obj=new abc
then it is allocated heap memory.
if it is true,why it is so.
thanks...
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Question by:decentswati
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aviadbd earned 300 total points
ID: 12305469

When you allocate memory using the "new" operator, your operating system searches for a free memory in the virtual memory the application get when it is started.  The benefit of the heap is that it is not released until you specificly delete it with the "delete" operator.

The stack, however, is more connected to the scope the object being allocated. So, it is automaticly deleted when you leave that scope.

Further, heap is usually allocated at run-time while stack is allocated (more or less) in compile-time.

Try reading more here:
http://www-ee.eng.hawaii.edu/Courses/EE150/Book/chap14/subsection2.1.1.8.html

AviadBD.
 
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by:avizit
avizit earned 75 total points
ID: 12305806
>>i heard that if we declare an object like
>>abc obj;
>>{assuming abc is a class}
>>it is allocated stack memory

Not entirely true, only true if the line "abj obj;" is inside a function ,

in case the object obj is global , its is allocated neither in heap or stack.

check "overview of c++ memory management" http://www.cse.wustl.edu/~cdgill/courses/cs342/c++_memory_management.pdf
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Expert Comment

by:aviadbd
ID: 12306004

True, avizit.

Also, if there is a member declaration inside a class, it will not be allocated at all until the class itself is allocated.

AviadBD.
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Expert Comment

by:stefan73
ID: 12306089
Hi aviadbd,
> Also, if there is a member declaration inside a class, it will not be
> allocated at all until the class itself is allocated.

...unless it's static. Then it's "somehow" allocated at program start, with no guaranteed order.

Cheers!

Stefan
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