Avoid potential integer overflows and improve consistency. This should

fix bug #13918 "Segfault with precision = MPFR_PREC_MAX on 32-bit".
Note: this problem appeared in MPFR 3.0.0 when the precision type (now
mpfr_prec_t) was changed to a signed integer.

git-svn-id: svn://scm.gforge.inria.fr/svn/mpfr/trunk@8025 280ebfd0-de03-0410-8827-d642c229c3f4

1 files changed, 9 insertions, 2 deletions

diff --git a/src/urandomb.c b/src/urandomb.c
index f8597075d..3e941e7bc 100644
--- a/src/urandomb.c
+++ b/src/urandomb.c
@@ -31,13 +31,20 @@ http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
    a sufficient number of limbs */
 void
 mpfr_rand_raw (mpfr_limb_ptr mp, gmp_randstate_t rstate,
-               unsigned long int nbits)
+               mpfr_prec_t nbits)
 {
   mpz_t z;
 
+  MPFR_ASSERTN (nbits >= 1);
   /* To be sure to avoid the potential allocation of mpz_urandomb */
-  ALLOC(z) = SIZ(z) = ((nbits - 1) / GMP_NUMB_BITS) + 1;
+  ALLOC(z) = SIZ(z) = MPFR_PREC2LIMBS (nbits);
   PTR(z)   = mp;
+#if __MPFR_GMP(5,0,0)
+  /* Check for integer overflow (unless mp_bitcnt_t is signed,
+     but according to the GMP manual, this shouldn't happen).
+     Note: mp_bitcnt_t has been introduced in GMP 5.0.0. */
+  MPFR_ASSERTN ((mp_bitcnt_t) -1 < 0 || nbits <= (mp_bitcnt_t) -1);
+#endif
   mpz_urandomb (z, rstate, nbits);
 }