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Date: Fri, 14 Nov 2003 10:47:47 -0500
From: "Robert I. Eachus" <rieachus@comcast.net>
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Subject: Re: C's trikery semantic opens up backdoor in new Linux kernel
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Date: 2003-11-14T10:47:47-05:00
List-Id: <comp.lang.ada>

Vinzent 'Gadget' Hoefler wrote:

>>>For instance considering the simple rule that in a comparison with a
>>>
>>>constant value you should always state the constant first:
>>>|if ((__WCLONE|__WALL) == options) && (0 = current->uid))
>>>
>>>wouldn't compile, either.
>>
>>No, but do you really think such a style could be enforced in the linux
>>kernel community?

> No. And you? Do you really think that the linux kernel community would
> like the idea of using a *function* to get/set a plain simple integer
> variable? I already hear them scream: "It would be too inefficient.
> Especially in a *kernel*!" ;-)

Bad example here.  GCC will print a warning message about assignment in 
condition clauses unless the assignment is enclosed in parentheses. So:

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

-- 
                                           Robert I. Eachus

100% Ada, no bugs--the only way to create software.