[alsa-devel] bug report: aloop: potential signedness bug in loopback_prepare()

[Dan Carpenter]

On Sat, Oct 09, 2010 at 02:14:30PM +0200, Jaroslav Kysela wrote:
> On Sat, 9 Oct 2010, Dan Carpenter wrote:
>
>> Hi Jaroslav,
>>
>> sound/drivers/aloop.c +287 loopback_prepare(10)
>> 	warn: bogus compare against zero: 'bps'
>>   282          unsigned int bps, salign;
>>   283
>>   284          salign = (snd_pcm_format_width(runtime->format) *
>>   285							runtime->channels) / 8;
>>   286          bps = salign * runtime->rate;
>>   287          if (bps <= 0 || salign <= 0)
>>                    ^^^^^^^^^^^^^^^^^^^^^^^
>>
>>
>> 	Both "bps" and "salign" are unsigned and are never less than
>> 	zero.  Should this just be checking for == 0?  Or was the check
>> 	supposed to catch integer overflows?
>
> The condition works for both signed and unsigned values. That was only  
> reason why I did not write '==' there.
>
> 					Jaroslav
>

What I mean is that the less than zero part is never true.  For example,
the following test program will print "more" instead of "less".

regards,
dan carpenter

#include <stdio.h>

int main(int argc, char **argv)
{
	unsigned int x = -3;

	if (x <= 0)
		printf("less\n");
	else
		printf("more\n");

	return 0;
}