Re: Do not misuse Coverity please (Was: sound/oss/cs46xx.c: fix a check after use)

[Horst von Brand]

"Jean Delvare" <khali@xxxxxxxxxxxx> said:

[Sttributions missing, sorry]

> > >  Think about it. If the pointer could be NULL, then it's unlikely that
> > >  the bug would have gone unnoticed so far (unless the code is very
> > >  recent). Coverity found 3 such bugs in one i2c driver [1], and the
> > >  correct solution was to NOT check for NULL because it just couldn't
> > >  happen.

> > No, there is a third case: the pointer can be NULL, but the compiler
> > happened to move the dereference down to after the check.

> Wow. Great point. I completely missed that possibility. In fact I didn't
> know that the compiler could possibly alter the order of the
> instructions. For one thing, I thought it was simply not allowed to. For
> another, I didn't know that it had been made so aware that it could
> actually figure out how to do this kind of things. What a mess. Let's
> just hope that the gcc folks know their business :)

The compiler is most definitely /not/ allowed to change the results the
code gives.
-- 
Dr. Horst H. von Brand                   User #22616 counter.li.org
Departamento de Informatica                     Fono: +56 32 654431
Universidad Tecnica Federico Santa Maria              +56 32 654239
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