log.c: avoid mpfr_get_exp and mpfr_can_round on 0

git-svn-id: svn://scm.gforge.inria.fr/svn/mpc/trunk@1219 211d60ee-9f03-0410-a15a-8952a2c7a4e4

1 files changed, 4 insertions, 0 deletions

diff --git a/src/log.c b/src/log.c
index f60fee1..822dea5 100644
--- a/src/log.c
+++ b/src/log.c
@@ -135,6 +135,10 @@ mpc_log (mpc_ptr rop, mpc_srcptr op, mpc_rnd_t rnd){
       mpfr_log (w, w, GMP_RNDN);
          /* generic error of log: (2^(- exp(w)) + 0.5) ulp */
 
+      if (mpfr_zero_p (w))
+         /* impossible to round, switch to second algorithm */
+         break;
+
       err = MPC_MAX (-mpfr_get_exp (w), 0) + 1;
          /* number of lost digits */
       ok = mpfr_can_round (w, prec - err, GMP_RNDN, GMP_RNDZ,