Basic C.
> Take this example program:
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <math.h>
>
> int
> main(void)
> {
> uint32_t n = arc4random();
>
> printf("arc4random %d\n", n);
> printf("abs %d\n", abs(n));
>
> return 0;
> }
>
> It gives the following warning when compiling:
>
> test.c:11:21: warning: taking the absolute value of unsigned type
> 'uint32_t' (aka 'unsigned int') has no effect [-Wabsolute-value]
> printf("abs %d\n", abs(n));
> ^
> test.c:11:21: note: remove the call to 'abs' since unsigned values
> cannot be negative
> printf("abs %d\n", abs(n));
> ^~~
>
> Which is well and good. However, I get the following output.
>
> laptop$ ./a.out
> arc4random 247165650
> abs 247165650
> laptop$ ./a.out
> arc4random 2012715611
> abs 2012715611
> laptop$ ./a.out
> arc4random 222644175
> abs 222644175
> laptop$ ./a.out
> arc4random -843593186
> abs 843593186
>
> So on the fourth try I got what appears to be a negative number back.
> I'm not sure if this is some printf() funny business or what. Please
> explain. In real life I don't intend on using this with printf() so If
> thats the case no worries. However, if not I need to know that my random
> number is positive. I also tried if (n < 0) etc.. and got similar warnings.
>
> Thanks in advance,
>
> Edgar
>
