Re: quartz: Check allocation failure and clear memory in DSound Renderer

[Detlef Riekenberg]

On Fr, 2007-03-09 at 03:02 -0800, Chris Robinson wrote:
> - ZeroMemory(pDSoundRender, sizeof(DSoundRenderImpl));

Since you clear the whole struct, ...
>  pDSoundRender->lpVtbl = &DSoundRender_Vtbl;
>  pDSoundRender->IBasicAudio_vtbl = &IBasicAudio_Vtbl;
>
> @@ -325,9 +328,15 @@ HRESULT DSoundRender_create(IUnknown * pUnkOuter,
> LPVOID * ppv)
>      pDSoundRender->pClock = NULL;
>      pDSoundRender->init = FALSE;
>      pDSoundRender->started = FALSE;

... there is no need to clear it again.

quartz: Check allocation failure and clear memory in DSound Renderer

[Felix Nawothnig]

Detlef Riekenberg wrote:
> > @@ -325,9 +328,15 @@ HRESULT DSoundRender_create(IUnknown * pUnkOuter,
> > LPVOID * ppv)
> >     pDSoundRender->pClock = NULL;
> >     pDSoundRender->init = FALSE;
> >     pDSoundRender->started = FALSE;
>
> ... there is no need to clear it again.

However, note that NULL is not always all binary zero in memory. :)

quartz: Check allocation failure and clear memory inDSound Renderer

[Dmitry Timoshkov]

"Felix Nawothnig"  wrote:
> However, note that NULL is not always all binary zero in memory. :)

I don't believe it's true since NULL is defined as (void *)0.

quartz: Check allocation failure and clear memory inDSound Renderer

[Felix Nawothnig]

Dmitry Timoshkov wrote:
> > However, note that NULL is not always all binary zero in memory. :)
>
> I don't believe it's true since NULL is defined as (void *)0.

Actually it may aswell be just 0 in C. Just in C++ it's defined to be 
(void *)0. But even with just 0 an assignment/compare/whatever will get 
you an implicit typecast which makes the compiler generate any necessary 
conversion.

See http://c-faq.com/null/

Felix

quartz: Check allocation failure and clear memoryinDSound Renderer

[Dmitry Timoshkov]

"Felix Nawothnig"  wrote:
> Dmitry Timoshkov wrote:
> > > However, note that NULL is not always all binary zero in memory. :)
> >
> > I don't believe it's true since NULL is defined as (void *)0.
>
> Actually it may aswell be just 0 in C. Just in C++ it's defined to be 
> (void *)0. But even with just 0 an assignment/compare/whatever will get 
> you an implicit typecast which makes the compiler generate any necessary 
> conversion.
>
> See http://c-faq.com/null/

Have you read it at all? NULL is guaranteed to be 0 in all contexts.

If some C++ compiler decides to generate not 0 data while converting/casting
a NULL pointer, it should be declared broken.

quartz: Check allocation failure and clear memoryinDSound Renderer

[Alexandre Julliard]

"Dmitry Timoshkov"  writes:
> Have you read it at all? NULL is guaranteed to be 0 in all contexts.
>
> If some C++ compiler decides to generate not 0 data while converting/casting
> a NULL pointer, it should be declared broken.

The point is that (void*)0 isn't guaranteed to be represented by an
all-zero bit pattern; but that's the case on any platform worth
worrying about.

quartz: Check allocation failure and clearmemoryinDSound Renderer

[Dmitry Timoshkov]

"Alexandre Julliard"  wrote:
> The point is that (void*)0 isn't guaranteed to be represented by an
> all-zero bit pattern; but that's the case on any platform worth
> worrying about.

If (void*)0 doesn't guarantee to actually set all bits to 0, then
HEAP_ZERO_MEMORY doesn't guarantee it either.

quartz: Check allocation failure and clearmemoryinDSound Renderer

[Alexandre Julliard]

"Dmitry Timoshkov"  writes:
> If (void*)0 doesn't guarantee to actually set all bits to 0, then
> HEAP_ZERO_MEMORY doesn't guarantee it either.

Yes, that's the point. In theory you have to initialize things with an
explicit assignment, instead of a memset or HEAP_ZERO_MEMORY. In
practice it doesn't matter.

quartz: Check allocation failure and clear memory in DSound Renderer

[Francois Gouget]

On Fri, 9 Mar 2007, Felix Nawothnig wrote:
> Detlef Riekenberg wrote:
> > > @@ -325,9 +328,15 @@ HRESULT DSoundRender_create(IUnknown * pUnkOuter,
> > > LPVOID * ppv)
> > >     pDSoundRender->pClock = NULL;
> > >     pDSoundRender->init = FALSE;
> > >     pDSoundRender->started = FALSE;
> >
> > ... there is no need to clear it again.
>
> However, note that NULL is not always all binary zero in memory. :)

Isn't it zero on all sane systems, i.e. all systems we care about and 
even more?