Re: [avr-gcc-list] Re: WinAVR 20050214 (gcc 3.4.3) and optimizer bug.

[E. Weddington]

Vesa Jääskeläinen wrote:

> Joerg Wunsch wrote:
>
> > As Vesa Jääskeläinen wrote:
> >
> > > I have been debugging why Ethernut brakes in certain situations with
> > > gcc. And found an optimizer bug.
>
> In this clause:
>         if (ppv && (*ppv != 0)) {
>
> We are missing code for (ppv != 0), but code for *ppv != 0 is found. And
>  if I pass NULL to this function it makes compare to incorrect memory
> location.

Regardless of whether there is a compiler bug, the above is incorrect C. 
You are NEVER supposed to rely on the fact that a NULL pointer is equal 
to zero, because, technically, it can be defined as something else. You 
should always directly compare a pointer to NULL as such:

if(ppv != NULL && (*ppv != 0))

Eric