added example which triggers a bug in mpc_div

2 files changed, 12 insertions, 0 deletions

diff --git a/src/div.c b/src/div.c
index 17f8876..a5395ab 100644
--- a/src/div.c
+++ b/src/div.c
@@ -312,7 +312,13 @@ mpc_div (mpc_ptr a, mpc_srcptr b, mpc_srcptr c, mpc_rnd_t rnd)
             hopefully, the side-effects of mpc_mul do indeed raise the
             mpfr exceptions */
       if (overflow_prod) {
+        /* FIXME: in case overflow_norm is also true, the code below is wrong,
+           since the after division by the norm, we might end up with finite
+           real and/or imaginary parts. A workaround would be to scale the
+           inputs (in case the exponents are within the same range). */
          int isinf = 0;
+         /* determine if the real part of res is the maximum or the minimum
+            representable number */
          tmpsgn = mpfr_sgn (mpc_realref(res));
          if (tmpsgn > 0)
            {
@@ -331,6 +337,7 @@ mpc_div (mpc_ptr a, mpc_srcptr b, mpc_srcptr c, mpc_rnd_t rnd)
              mpfr_set_inf (mpc_realref(res), tmpsgn);
              overflow_re = 1;
            }
+         /* same for the imaginary part */
          tmpsgn = mpfr_sgn (mpc_imagref(res));
          isinf = 0;
          if (tmpsgn > 0)
diff --git a/tests/div.dat b/tests/div.dat
index b030382..b3d7fee 100644
--- a/tests/div.dat
+++ b/tests/div.dat
@@ -2484,3 +2484,8 @@
 - - 2 0 2 0x1p-1073741823 2 0x3p-1073741824 2 0x1p-1073741823 2 1 2 -1 Z Z
 # (1.5+i)*2^emin/(1+i) gives (1.25 - 0.25*i)*2^emin
 - + 2 0x1p-1073741823 2 -0 2 0x3p-1073741824 2 0x1p-1073741823 2 1 2 1 Z Z
+
+# example with exact division (0 -1) which works:
+0 0 2 0 2 -1 2 -0x1p50450368 2 0x1p50450368 2 -0x1p50450368 2 -0x1p50450368 N N
+# same with larger exponents, which gives (0 -Inf) in revision 389c43d:
+0 0 2 0 2 -1 2 -0x1p550450368 2 0x1p550450368 2 -0x1p550450368 2 -0x1p550450368 N N