On 08/29/2013 10:33 AM, Eric Blake wrote:
> Since gnulib has a working random_r() function can we just make
> gnulib replace the boneheaded freebsd impl ?
Huh - the glibc man pages state that random_r returns RAND_MAX bits.
random_r is a glibc extension: POSIX only requires rand(), rand_r(), and
random(); but even with random(), POSIX has no requirements that it be
related to RAND_MAX - so the fact that glibc equates random()/random_r()
with RAND_MAX is also a glibc extension.
I guess that means we should't be worrying about RAND_MAX in the first
place, as it is tied to the (potentially algorithmically weaker) rand(),
and need not have any bearing on the fact that we already use gnulib's
random_r().
I'll play around with a patch.
As it is, POSIX recommends the use of drand48() and friends for
multithreaded apps, not random() (where lrand48() would match precisely
with a RAND_MAX of 0x7fffffff); but that's because POSIX lacks
random_r(). But since gnulib lacks [dl]rand48(), I still think libvirt
is still better off sticking with random_r(), and just avoiding the red
herring of a potentially unrelated RAND_MAX.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library
http://libvirt.org