[cmake-developers] OpenBSD and srand()/rand() changes

[Brad King]

On 12/14/2014 08:36 AM, Rolf Eike Beer wrote:
> The idea behind this API in OpenBSD is: if you are looking for the pseudo 
> numbers you need to call srand_deterministic(), i.e. you must explicitely 
> state that you want the not really random random numbers. Everyone else will 
> get real random.

CMake uses /dev/urandom on POSIX and wincrypt APIs on Windows to choose
the seed specifically to get "really" random behavior.  The *only* reason
we continue to use s/rand() at all is to support the RANDOM_SEED API in
string(RANDOM), AFAIK.

One approach to dealing with this is to refactor the implementation of
string(RANDOM) to use non-deterministic APIs until RANDOM_SEED is used
and then use deterministic APIs after that.  That will get better random
values by default but still honor the existing API when it is used.

-Brad