Make division by zero cause `ZeroDivisionError`.

As described in ISO 15.2.30.

6 files changed, 24 insertions, 25 deletions

diff --git a/doc/limitations.md b/doc/limitations.md
index 7e58ca420..8ac959b98 100644
--- a/doc/limitations.md
+++ b/doc/limitations.md
@@ -63,8 +63,15 @@ end
 
 #### mruby [2.1.2 (2020-08-06)]
 
-No exception is raised.
+No exception is raised. Instead you have to do:
 
+```ruby
+begin
+  1 / 0
+rescue => e
+  raise e
+end
+```
 ## Fiber execution can't cross C function boundary
 
 mruby's `Fiber` is implemented in a similar way to Lua's co-routine. This
diff --git a/include/mruby.h b/include/mruby.h
index f07adbb13..959d1ac6d 100644
--- a/include/mruby.h
+++ b/include/mruby.h
@@ -1292,6 +1292,7 @@ MRB_API mrb_value mrb_vformat(mrb_state *mrb, const char *format, va_list ap);
 */
 #define E_RUNTIME_ERROR             (mrb_exc_get_id(mrb, MRB_SYM(RuntimeError)))
 #define E_TYPE_ERROR                (mrb_exc_get_id(mrb, MRB_SYM(TypeError)))
+#define E_ZERODIV_ERROR             (mrb_exc_get_id(mrb, MRB_SYM(ZeroDivisionError)))
 #define E_ARGUMENT_ERROR            (mrb_exc_get_id(mrb, MRB_SYM(ArgumentError)))
 #define E_INDEX_ERROR               (mrb_exc_get_id(mrb, MRB_SYM(IndexError)))
 #define E_RANGE_ERROR               (mrb_exc_get_id(mrb, MRB_SYM(RangeError)))
diff --git a/mrblib/10error.rb b/mrblib/10error.rb
index 0d9f38d58..054603514 100644
--- a/mrblib/10error.rb
+++ b/mrblib/10error.rb
@@ -21,6 +21,10 @@ end
 class TypeError < StandardError
 end
 
+# ISO 15.2.30
+class ZeroDivisionError < StandardError
+end
+
 # ISO 15.2.31
 class NameError < StandardError
   attr_accessor :name
diff --git a/src/numeric.c b/src/numeric.c
index 99d32f919..0cc7958e6 100644
--- a/src/numeric.c
+++ b/src/numeric.c
@@ -156,7 +156,7 @@ integral_div(mrb_state *mrb, mrb_value xv)
 
   mrb_get_args(mrb, "i", &y);
   if (y == 0) {
-    mrb_raise(mrb, E_RUNTIME_ERROR, "devided by zero");
+    mrb_raise(mrb, E_ZERODIV_ERROR, "devided by zero");
   }
   return mrb_fixnum_value(mrb_fixnum(xv) / y);
 #else
@@ -932,14 +932,7 @@ int_mod(mrb_state *mrb, mrb_value x)
     mrb_int mod;
 
     if (b == 0) {
-#ifdef MRB_NO_FLOAT
-      /* ZeroDivisionError */
-      return mrb_fixnum_value(0);
-#else
-      if (a > 0) return mrb_float_value(mrb, INFINITY);
-      if (a < 0) return mrb_float_value(mrb, INFINITY);
-      return mrb_float_value(mrb, NAN);
-#endif
+      mrb_raise(mrb, E_ZERODIV_ERROR, "divided by 0");
     }
     fixdivmod(mrb, a, b, NULL, &mod);
     return mrb_fixnum_value(mod);
@@ -971,14 +964,7 @@ int_divmod(mrb_state *mrb, mrb_value x)
     mrb_int div, mod;
 
     if (mrb_fixnum(y) == 0) {
-#ifdef MRB_NO_FLOAT
-      return mrb_assoc_new(mrb, mrb_fixnum_value(0), mrb_fixnum_value(0));
-#else
-      return mrb_assoc_new(mrb, ((mrb_fixnum(x) == 0) ?
-                                 mrb_float_value(mrb, NAN):
-                                 mrb_float_value(mrb, INFINITY)),
-                           mrb_float_value(mrb, NAN));
-#endif
+      mrb_raise(mrb, E_ZERODIV_ERROR, "divided by 0");
     }
     fixdivmod(mrb, mrb_fixnum(x), mrb_fixnum(y), &div, &mod);
     return mrb_assoc_new(mrb, mrb_fixnum_value(div), mrb_fixnum_value(mod));
diff --git a/src/vm.c b/src/vm.c
index 979c67424..15a38c0e4 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -2315,12 +2315,13 @@ RETRY_TRY_BLOCK:
         {
           mrb_int x = mrb_fixnum(regs[a]);
           mrb_int y = mrb_fixnum(regs[a+1]);
-          if (y == 0 || (x == MRB_INT_MIN && y == -1)) {
-#ifdef MRB_NO_FLOAT
-            SET_INT_VALUE(regs[a], y ? x / y : 0);
-#else
-            SET_FLOAT_VALUE(mrb, regs[a], (mrb_float)x / (mrb_float)y);
-#endif
+
+          
+          if (y == 0) {
+            mrb_raise(mrb, E_ZERODIV_ERROR, "divided by 0");
+          }
+          else if(x == MRB_INT_MIN && y == -1) {
+            mrb_raise(mrb, E_RANGE_ERROR, "integer overflow in division");
           }
           else {
             mrb_int div, mod;
diff --git a/test/t/superclass.rb b/test/t/superclass.rb
index 10b6438d3..70d5c24d9 100644
--- a/test/t/superclass.rb
+++ b/test/t/superclass.rb
@@ -29,7 +29,7 @@
   [:RegexpError, :StandardError, '12.2.27.2'],
   [:RuntimeError, :StandardError, '12.2.28.2'],
   [:TypeError, :StandardError, '12.2.29.2'],
-#  [:ZeroDivisionError, :StandardError, '12.2.30.2'],  # No ZeroDivisionError in mruby
+  [:ZeroDivisionError, :StandardError, '12.2.30.2'],
   [:NameError, :StandardError, '15.2.31.2'],
   [:NoMethodError, :NameError, '15.2.32.2'],
   [:IndexError, :StandardError, '15.2.33.2'],