Re: [HACKERS] random() function produces wrong range

Malcolm Beattie <mbeattie(at)sable(dot)ox(dot)ac(dot)uk> writes:
> Tom Lane writes:
>> Thomas Lockhart <lockhart(at)alumni(dot)caltech(dot)edu> writes:
>>>> The Linux man pages indicate that the behavior and underlying
>>>> implementation of random() and rand() are the same (so I just picked
>>>> one).
>>
>> Ah, well, there's your problem. Whoever did this part of the library
>> on Linux took shortcuts.

> Why? Linux is compliant with the Single Unix Standard v2 from my brief
> reading of it.

Sorry, bad choice of words on my part. Linux is within its rights to
use the same underlying implementation for rand() and random(), but it
is a poor guide to the behavior of other systems, which are equally
within their rights not to.

>> none of the man pages I've looked at so far mention it). But all the
>> machines say that the output of random() is 31 bits, so INT_MAX should
>> work.

> SuSv2 says explicitly 2^31-1 so you should use that, otherwise you'll
> be non-portable to platforms with 64-bit ints, for example.

Maybe. You don't think that a 64-bit-int platform would choose to
supply a random() function with a range of 2^63-1? The HPUX and SunOS
man pages clearly specify that random()'s result is "long", so I think
a case could also be made for LONG_MAX.

I suspect we have a good chance at getting burned no matter what we use
:-(. But RAND_MAX is definitely the wrong thing.

regards, tom lane