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