Problem with gmp_randinit_set

[Torbjörn Granlund]

   gmp_randinit_set(b, a);
   gmp_randseed_ui(b, 123456); /* crashes */
  
  AFAICT this is a gmp bug, but I don't rule out the possibility that
  it's a user bug.
  
This looks like a GMP bug.

I never looked properly through the GMP PRNG code, and looking at it now
I don't immediately understand its structure.  (This code was written by
an external contributor.)

What happens with your code is that GMP tries to call a seed application
function through a pointer, but that pointer was explicitly zeroed by
gmp_randinit_set (or in __gmp_randiset_mt to be exact).

One can change Mersenne_Twister_Generator_Noseed to
Mersenne_Twister_Generator to fix this (and move __gmp_randiset_mt to
randmts.c as mandated by Mersenne_Twister_Generator's scope), and then
your code supposedly runs without a crash.  But I don't see why one ever
wants Mersenne_Twister_Generator_Noseed, which suggests my understanding
of this code is very poor indeed.

-- 
Torbjörn
Please encrypt, key id 0xC8601622