add function for checked mrb_int subtraction

1 files changed, 1 insertions, 3 deletions

diff --git a/src/numeric.c b/src/numeric.c
index 8ea71ada6..7b025c34d 100644
--- a/src/numeric.c
+++ b/src/numeric.c
@@ -1145,9 +1145,7 @@ mrb_fixnum_minus(mrb_state *mrb, mrb_value x, mrb_value y)
     mrb_int b, c;
 
     b = mrb_fixnum(y);
-    c = a - b;
-    if (((a < 0) ^ (b < 0)) != 0 && (a < 0) != (c < 0)) {
-      /* integer overflow */
+    if (mrb_int_sub_overflow(a, b, &c)) {
       return mrb_float_value(mrb, (mrb_float)a - (mrb_float)b);
     }
     return mrb_fixnum_value(c);