On changing rand(3) to random(3) in awk(1)

[Peter Pentchev]

On Thu, Aug 28, 2014 at 09:28:48PM +0800, Chenguang Li wrote:
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> > Peter Pentchev <roam at ringlet.net> wrote:
> >> On Thu, Aug 28, 2014 at 12:51:52PM +0300, Vitaly Magerya wrote:
> >>> On 2014-08-28 09:21, Chenguang Li wrote:
> >>> [snip]
> >>> Index: run.c
> >>> ===================================================================
> >>> --- run.c       (revision 270740)
> >>> +++ run.c       (working copy)
> >>> @@ -1522,7 +1522,7 @@
> >>>               break;
> >>>       case FRAND:
> >>>               /* in principle, rand() returns something in 0..RAND_MAX */
> >>> -               u = (Awkfloat) (rand() % RAND_MAX) / RAND_MAX;
> >>> +               u = (Awkfloat) (random() % RAND_MAX) / RAND_MAX;
> >> 
> >> You should not use RAND_MAX with random(3), since it returns values
> >> between 0 and 0x7fffffff (inclusive); RAND_MAX only applies to rand(3).
> >> 
> >> A better patch would be something like this:
> >> 
> >> -               /* in principle, rand() returns something in 0..RAND_MAX */
> >> -               u = (Awkfloat) (rand() % RAND_MAX) / RAND_MAX;
> >> +               /* random() returns values in [0, 2147483647] */
> >> +               u = (Awkfloat) random() / 2147483648;
> >
> > Hm.  Since random() is documented to return "long", wouldn't it be a bit
> > better with #include <limits.h> and LONG_MAX here?
> 
> I am using RANDOM_MAX here to maintain the original code structure.
> I've updated my patch, please check the gist. Thanks!

Right, but you've hard-coded RANDOM_MAX to 2^32-1.  I don't think this
is correct; I do believe that you should use LONG_MAX for this value.
Of course, #define RANDOM_MAX LONG_MAX could be fine for this purpose
here, but the point is to use LONG_MAX instead of 2^32-1.

G'luck,
Peter

-- 
Peter Pentchev  roam at ringlet.net roam at FreeBSD.org p.penchev at storpool.com
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