What happens exactly during run time?

[Pranav]

class just{
public :
int x;
just(){ x=1234; }
just(int i){ x = i;}
~just(){ cout << " Here We Are\n" ;}
};

int main()
{
just j1;
just *jptr =new just(5432);

delete( jptr);
delete( &j1);

cout << "Test Out \n" ;

return 0;
}

After executing destructor for J1 program calls for an abort in Visual
Studio 6

[tni]

tni wrote:

'new' will first call the destructor, then call 'free'.

I meant 'delete' of course.

[Rolf Magnus]

tni wrote:

Pranav wrote:

>>
Ya I know that thing, But When I call 'delete(&j1)' the destructor for
'j1' is called after this there is window appears saying 'Abort/Ignore/
Retry'. Why exactly this behaviour occurs? Can any one explain what
happens during runtime?

'new' will first call the destructor, then call 'free'.

Not exactly. It will do something similar to 'free'. On some compilers, it
actually does call 'free', but that's not required by the standard.

[tni]

Rolf Magnus wrote:

tni wrote:

>'delete' will first call the destructor, then call 'free'.

Not exactly. It will do something similar to 'free'. On some compilers, it
actually does call 'free', but that's not required by the standard.

He said he was using Visual C++. It does use malloc/free in new/delete.

[Pranav]

On Aug 12, 2:08 pm, tni <nob...@example .comwrote:

Rolf Magnus wrote:

tni wrote:

'delete' will first call the destructor, then call 'free'.

Not exactly. It will do something similar to 'free'. On some compilers, it
actually does call 'free', but that's not required by the standard.

He said he was using Visual C++. It does use malloc/free in new/delete.

Recently I read from a book that free() does not call destructor for
objects properly and also for array of user defined objects. Is it
true?
Also I came through, allocator allocate an extra word of memory
specifying the size of the array from which deallocating function gets
the size of array and this word of memory usually right before the
start address returned by the allocator.

[Ian Collins]

Pranav wrote:

On Aug 12, 2:08 pm, tni <nob...@example .comwrote:

>Rolf Magnus wrote:

>>tni wrote:
'delete' will first call the destructor, then call 'free'.
Not exactly. It will do something similar to 'free'. On some compilers, it
actually does call 'free', but that's not required by the standard.

He said he was using Visual C++. It does use malloc/free in new/delete.

Recently I read from a book that free() does not call destructor for
objects properly and also for array of user defined objects. Is it
true?

Yes, free() is just a C library function frees memory previously
allocated with one of the malloc() family of functions. It knows
nothing of C++ classes.

Operators new and delete may call malloc() and free() to allocate and
free memory, but that is only part of their jobs. The other part is
constructing and destructing the objects.

Assuming they do, operator new will call malloc to allocate memory and
then call the object's constructor. Operator delete will call the
object's destructor and then call free to release the memory.

--
Ian Collins.

[Pranav]

On Aug 12, 3:05 pm, Ian Collins <[e-mail] mwrote:

Pranav wrote:

On Aug 12, 2:08 pm, tni <nob...@example .comwrote:

Rolf Magnus wrote:
tni wrote:
'delete' will first call the destructor, then call 'free'.
Not exactly. It will do something similar to 'free'. On some compilers, it
actually does call 'free', but that's not required by the standard.
He said he was using Visual C++. It does use malloc/free in new/delete.

Recently I read from a book that free() does not call destructor for
objects properly and also for array of user defined objects. Is it
true?

Yes, free() is just a C library function frees memory previously
allocated with one of the malloc() family of functions. It knows
nothing of C++ classes.

Operators new and delete may call malloc() and free() to allocate and
free memory, but that is only part of their jobs. The other part is
constructing and destructing the objects.

Assuming they do, operator new will call malloc to allocate memory and
then call the object's constructor. Operator delete will call the
object's destructor and then call free to release the memory.

--
Ian Collins.

Exactly.., Thank You All, for clarifying my doubts..,
Pranav

--There's a difference between knowing the path and walking it.