On Tue, 25 Jan 2011, Peter Hüwe wrote: > Am Dienstag 25 Januar 2011, 23:20:44 schrieb Julia Lawall: > > On Tue, 25 Jan 2011, Peter Huewe wrote: > > > This patch fixes the warning "Using plain integer as NULL pointer", > > > generated by sparse, by replacing the offending 0s with NULL. > > > > I recall (a number of years ago) being told that for things like kmalloc, > > the proper test was !x, not x == NULL. > > > > julia > > > > > Hi Julia, > > thanks for your input. > So do I understand you correctly if I say > if(!x) is better than if(x==NULL) in any case? No. > Or only for the kmalloc family? > > Do you remember the reason why !x should be preferred? Because it is a function call, and NULL represents failure of that function, not an actual NULL value. Here is an email that explains that: http://lkml.org/lkml/2007/7/27/103 Here is the beginning of the thread: http://lkml.org/lkml/2007/7/27/75 julia > In Documentation/CodingStyle , Chapter 7: Centralized exiting of functions > there is a function fun with looks like this: > int fun(int a) > { > int result = 0; > char *buffer = kmalloc(SIZE); > > if (buffer == NULL) > return -ENOMEM; > > if (condition1) { > while (loop1) { > ... > } > result = 1; > goto out; > } > ... > out: > kfree(buffer); > return result; > } > > > --> So if (buffer == NULL) is in the official CodingStyle - maybe we should > add a paragraph there as well ;) > > > Don't get me wrong, I just want to learn ;) > > > Thanks, > Peter > > -- > To unsubscribe from this list: send the line "unsubscribe kernel-janitors" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html >
