Re: C's trikery semantic opens up backdoor in new Linux kernel

[Vinzent 'Gadget' Hoefler <ada.rocks@jlfencey.com>]

Robert I. Eachus wrote:

>if (options == (__WCLONE|__WALL) && current->uid = 0)
>
>would generate a compiler warning message about the assignment to 
>current -> uid.  The Linux kernel coding standards make "redundant" 
>parentheses in conditions illegal for exactly that reason,

So you're saying that a style to use parentheses where it is not
*absolutely* clear which is meant is a bad style? Yes, I am talking
about operator precedence, this is especially bad in C where
programmer and compiler might have different opinions about a
particular construct and still it compiles.

>and one of 
>the things that made it clear that this was an intentional attempt to 
>get root was the "extra" parentheses.

The circumstances tell us that this was intentional, yes.

I'd use constants on the left side, but suppose I would not do that,
then I would more tend to write:

|if ((options == (__WCLONE|__WALL)) && (current->uid == 0))

without any bad ideas in mind.

Hmm. Now the typo, a job on a banking account system and, because I
wrote the parentheses, which in turn prove I was intentionally doing
that, I'm going to jail.


Vinzent.