Re: [ros-dev] [ros-diffs] [greatlrd] 22195: make malloc, calloc and some other function return NULL if size is 0

[Magnus Olsen]

Maybe we should add free to realloc and expand
to avoid memmory leak ??

I know realloc fail in windows it can create memory leak

text from internet how malloc should work

" If the size of the space requested is 0, the behavior is
implementation-defined:
  the value returned shall be either a null pointer or a unique pointer."


But most devloper assume malloc will return NULL if size is 0
 But some windows platfroms it return vaild pointer.

The question is how should we handle it in reactos,
return NULL or vaild pointer  for this case ?



----- Original Message ----- 
From: "Thomas Weidenmueller" <w3seek(a)reactos.com>
To: "ReactOS Development List" <ros-dev(a)reactos.org>
Sent: Saturday, June 03, 2006 4:39 PM
Subject: Re: [ros-dev] [ros-diffs] [greatlrd] 22195: make malloc, calloc and
some other function return NULL if size is 0


>   Royce Mitchell III wrote:
> > >   @@ -60,6
> > > +66,9 @@
> > >   */
> > >  void* realloc(void* _ptr, size_t _size)
> > >  {
> > >  +   if ( _size == 0)
> > >  +       return NULL;
> > >  +
> > >     if (!_ptr) return malloc(_size);
> > >     if (_size) return HeapReAlloc(hHeap, 0, _ptr, ROUND_SIZE(_size));
> > >     free(_ptr);
> > >  @@ -71,6 +80,9 @@
> > >   */
> > >
> > >  
> >  umm... shouldn't we call free() if we're going to return NULL because
> >  size is 0? 
>  realloc never frees the memory if it fails.
>
> >   Also, the free() at the bottom is never called
> > now. 
>  it's wrong and shouldn't even be there ;)
>
>  >> void* _expand(void* _ptr, size_t _size)
>  >> {
>  >> +   if ( _size == 0)
>  >> +       return NULL;
>  >> +
>  >>    return HeapReAlloc(hHeap, HEAP_REALLOC_IN_PLACE_ONLY, _ptr,
ROUND_SIZE(_size));
> > >   }
> > >
> > >  
> >  Again, shouldn't we free the existing buffer if we're returning NULL
> >  because size is 0? 
>  no, same as with realloc.
>
>  - Thomas
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