mpz_gcd segfault

[Tom Womack]

Summary: segfault in gmpn_gcd when computing the GCD of an enormous (1512583 
limbs) and a moderate (845 limbs) number

This was discovered for the enormous number = product of primes between 2^25 
and 2^26, and moderate number = 2^27038 with the base-10 digits reversed; 
since the enormous number is 6MB long, I hope I can get away with not 
attaching it.

Trying to replicate with

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include "gmp.h"

int main(int argc, char** argv)
{
 mpz_t A,B,C;
 gmp_randstate_t state;

 gmp_randinit_default(state);
 gmp_randseed_ui(state, 3);

 mpz_urandomb(A, state, 48402688);
 mpz_urandomb(B, state, 845*32);
 mpz_gcd(C,A,B);
}

gives a segfault in the mpz_urandomb call. Backtrace is

#0  0x4003d051 in __gmpn_copyi () from /usr/lib/libgmp.so.3
#1  0x40023012 in __gmp_randinit_lc_2exp () from /usr/lib/libgmp.so.3
#2  0x4002310d in __gmp_rand () from /usr/lib/libgmp.so.3
#3  0x400331f8 in __gmpz_urandomb () from /usr/lib/libgmp.so.3
#4  0x0804861b in main (argc=1, argv=0xbffffca4) at use-gcds-BUG.c:14

I'm using debian 3.0 (kernel 2.4.28), gcc-2.95.4 and gmp-4.0.1.

It may be this is all fixed in the current version of gmp; I've reported it 
to debian too.

Tom