On 21/03/12 1:37 PM, Jeremy C. Reed wrote:
My co-worker was troubleshooting why some of our unittests (that work on
multiple operating systems and architectures) failed on OpenBSD and saw
that if you call srandom(0) to initialize the RNG, random() will always
return 0. (I was able to reproduce this.)
If this is expected behaviour, please point to explanation.
He posted his tests and discussed the code related to this at:
https://banu.com/blog/42/openbsd-bug-in-the-random-function/
He suggests two ways to fix this:
1) if (x == 0)
x = 1;
upon entry in srandom(). That's the glibc way and he thinks is the
better solution as it falls back to the default behavior (when srandom
is not called) when the impossible seed=0 is passed.
2) the second way to fix it is the FreeBSD way:
for (i = 1; i< rand_deg; i++) {
+ if (state[i-1] == 0)
+ state[i-1] = 123459876;
val = div(state[i-1], 127773);
I assume you don't read the source-changes list.
CVSROOT: /cvs
Module name: src
Changes by: mill...@cvs.openbsd.org 2012/03/21 06:36:49
Modified files:
lib/libc/stdlib: random.c
Log message:
Fix a bug where random() always returns 0 when srandom() is seeded
with 0. Use 1 and not 0 as the first element of the state array,
similar to what glibc does. OK nicm@
--
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.
