Messages in this thread | | | Date | Wed, 5 Mar 2008 13:30:54 +0100 | From | "Bart Van Assche" <> | Subject | Re: [PATCH 6/9] drivers/net/wireless/iwlwifi/iwl-4965.c: Correct use of ! and & |
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On Wed, Mar 5, 2008 at 1:20 PM, Ingo Molnar <mingo@elte.hu> wrote: > > * Julia Lawall <julia@diku.dk> wrote: > > > There are some legitimate uses of !x & y which are actually of the > > form !x & !y, where x and y are function calls. That is a not > > particularly elegant way of getting both x and y to be evaluated and > > then combining the results using "and". If such code is considered > > acceptable, then perhaps the sparse patch should be more complicated. > > i tend to be of the opinion that the details in C source code should be > visually obvious and should be heavily simplified down from what is > 'possible' language-wise - with most deviations and complications that > depart from convention considered an error. I'd consider "!fn1() & > !fn2()" a borderline coding style violation in any case - and it costs > nothing to change it to "!fn1() && !fn2()".
If someone writes (!x & !y) instead of (!x && !y) because both x and y have to be evaluated, this means that both x and y have side effects. Please keep in mind that the C language does not specify whether x or y has to be evaluated first, so if x and y have to be evaluated in that order, an expression like (!x & !y) can be the cause of very subtle bugs. I prefer readability above brevity.
Bart Van Assche.
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