Vector new bug ??

Vector new bug ??

[Günter Neiß]

Hi,

 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.

 In that case I got an exeption inside 'builin vector new' (shown by
gdb).

 Ok, the workaroung is to check for this case:
 
 ...
  T * p;
  if( size == 0 )
    p = NULL;
   else
    p = new T[ size ];
 ...

 But I assume that this behaviour (or a similar one) should already
implemented inside (vector) new !

 I assume this, because this code was ported from Borland C++ (and works
under MS-C++ as well).

 I am not shure what the C++ standard says to this, but if it don't
specify it, 
 I assume returning NULL (or any unique pointer) should be the default
behaviour in this case
 ( as malloc( 0 ) does ).

 ...

Guenter

Re: Vector new bug ??

[Florian Weimer]

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Günter Neiß <gneiss@schoenhofer.de> writes:

> Hi,
>
>  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.
>
>  In that case I got an exeption inside 'builin vector new' (shown by
> gdb).

This is indeed a bug:

| When the value of the expression in a direct-new-declarator is zero,
| the allocation function is called to allocate an array with no
| elements.  The pointer returned by the new-expression is non-null.
| [Note: If the library allocation function is called, the pointer
| returned is distinct from the pointer to any other object.  ]

ISO/IEC 14882:1998, 5.3.4(7).

Re: Vector new bug ??

[Carlo Wood]

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On Fri, Oct 12, 2001 at 12:10:40PM +0200, Florian Weimer wrote:
> Günter Neiß <gneiss@schoenhofer.de> writes:
> >    t * p = new T[ size ];
> >  Everything works fine, as long as 'size' isn't 0.
> This is indeed a bug:
> 
> | When the value of the expression in a direct-new-declarator is zero,
> | the allocation function is called to allocate an array with no
> | elements.  The pointer returned by the new-expression is non-null.
> | [Note: If the library allocation function is called, the pointer
> | returned is distinct from the pointer to any other object.  ]
> 
> ISO/IEC 14882:1998, 5.3.4(7).

Weird that this is allowed, after all - zero elements for a normal
array isn't allowed either.

-- 
Carlo Wood <carlo@alinoe.com>