Re: Vector new bug ??

[Günter Neiß]

André Pönitz schrieb:

Thank's for Your answer.

 
> Günter Neiß <address@hidden> wrote:
> >  I found the following bug:
> >
> >  Using some templates that uses:
> >
> >  template<class T>
> >  ....
> >    t * p = new T[ size ];
> >
> >
> >  Everything works fine, as long as 'size' isn't 0.
> 
> Which version of g++ is that?
> 
> It seems to work in 2.95.2

That's the Version I am using...
.. and it doesn't work :-(((

 
> >   if( size == 0 )
> >     p = NULL;
> >    else
> >     p = new T[ size ];
> >  ...
> >
> >  But I assume that this behaviour should already implemented inside
> > (vector) new !
> 
> Note that there is a difference between an array of zero items and a null
> pointer.

.... it depends :-)) 

assuming: T = char

char * p = new char [ size ];

.. is really/nearly the same as 

char * p = (char*)malloc( size );

and this should be NULL in case of size==0...

But, ofcourse if new will return a seperate unique value, that's even
more sophisticated than returning NULL.

> >  I am not shure what the C++ standard says to this, but if it don't
> >  specify it, I assume returning NULL should be the default behaviour in
> >  this case ( as malloc( 0 ) does ).
> 
> Your assumption is wrong. From CD2 (similar wording in Final under 5.3.4.7)
> 
> 5.3.4
> 8 When the value of the expression in a direct-new-declarator  is  zero,
>   the  allocation  function  is called to allocate an array with no ele-
>   ments.  The pointer returned by the  new-expression  is  non-null  and
>   distinct from the pointer to any other object.

As stated above that's good, but isn't the case in my environment.
I got an exception instead.

BTW.: What's the meaning of 'direct-new-declarator' ??
      Is vector-new meant here ?


> Andre'
> 
> PS:
> 
> > application/x-pkcs7-signature; name="smime.p7s"
> > Content-Transfer-Encoding: base64 Content-Disposition: attachment;
> > filename="smime.p7s" Content-Description: Kryptographische Unterschrift
> > mit S/MIME
> 
> [Is this really necessary?]
Sorry, I forgot to disable signing for this forum

> André Pönitz .............................................. address@hidden
But this is (nearly) the same :-)))


Günter