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From: Ioannis Vranos <ivr@remove.this.grad.com>
Newsgroups: comp.lang.ada,comp.lang.c++,comp.realtime,comp.software-eng
Subject: Re: [OT] Re: Teaching new tricks to an old dog (C++ -->Ada)
Date: Mon, 28 Mar 2005 18:44:45 +0300
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Xref: g2news1.google.com comp.lang.ada:10072 comp.lang.c++:47610
 comp.realtime:1777 comp.software-eng:5412
Date: 2005-03-28T18:44:45+03:00
List-Id: <comp.lang.ada>

Ioannis Vranos wrote:

> In C++ you can always do:
> 
> #include <new>
> 
> 
> class SomeClass
> {
> };
> 
> 
> void somefunc()
> {
>     unsigned char obj[sizeof(SomeClass)];
> 
>     SomeClass *p= new(obj)SomeClass;
> 
>     delete p;
> }
> 
> 
> as also:
> 
> 
> #include <new>
> 
> 
> class SomeClass
> {
> };
> 
> 
> SomeClass *somefunc()
> {
>     static unsigned char obj[sizeof(SomeClass)];
> 
>     return new(obj)SomeClass;
> }
> 
> 
> int main()
> {
>     SomeClass *p= somefunc();
> 
>     delete p;
> }
> 
> 
> Here the object is created in the stack.


Of course, one can also do:

#include <iostream>
#include <new>


class SomeClassA
{
     int array[1024];
};

class SomeClassB
{
     public:
         SomeClassB() { std::cout<<"Constructor called!\n"; }
         ~SomeClassB() { std::cout<<"Destructor called!\n"; }
};


void somefunc()
{
     SomeClassA objA;

     SomeClassB *p= new(&objA) SomeClassB;

     delete p;
}



int main()
{
     somefunc();
}


corrupting objA in this way and invoking undefined behaviour.

But C++ is an enabling language, and not a prohibiting language. You can really do 
whatever you want, and provides some protection from accidental mistakes only, and not 
from intentional coding.




-- 
Ioannis Vranos

http://www23.brinkster.com/noicys

[I am using 90 characters word-wrapping - (800/640) *72= 90 or better described as: 
(800/640) *80 - 10 for quotation= 90. If someone finds it inconvenient, please let me know].