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SubjectRe: [PATCH 2.6.19] drivers/media/video/cpia2/cpia2_usb.c: Free previously allocated memory (in array elements) if kmalloc() returns NULL.
On Fri, 8 Dec 2006, Mariusz Kozlowski wrote:

> > > Just for future. Shorter and more readable version of your for(...) thing:
> > >
> > > while (i--) {
> > > ...
> > > }
> > >
> >
> > No, that is not equivalent.
> >
> > You want
> > while (i-- >= 0) {
> > ...
> > }
> >
>
> Not really. That will stop at -1 not 0.
>

It depends on your intent. Generally speaking,

while (i--) {
...
}

is never what you want. Adding the check for being greater than 0 stops
potential bugs from signed int i being negative. The only drawback on x86
is that it sets a byte based on the greater condition with setg and tests
it later with testb for every iteration. This use of testb will _always_
use the same addressable byte registers for both its operands.

Based on this particular patch, I agree that

while (i-- > 0) {
...
}

will do the job. This is equivalent to the original for loop and ensures
that a negative value of i is never iterated on (even though it admittedly
would never be negative in this instance to begin with).

David
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