Fixed a memory problem in Array#to_h

Reported from Alex Snaps via Mathieu Leduc-Hamel,
both from shopify.com.  Thank you!

include/mruby/array.h

@@ -134,6 +134,15 @@ mrb_ary_len(mrb_state *mrb, mrb_value ary)
   return RARRAY_LEN(ary);
 }
 
+static inline mrb_value
+ary_elt(mrb_value ary, mrb_int offset)
+{
+  if (offset < 0 || RARRAY_LEN(ary) <= offset) {
+    return mrb_nil_value();
+  }
+  return RARRAY_PTR(ary)[offset];
+}
+
 MRB_END_DECL
 
 #endif  /* MRUBY_ARRAY_H */

mrbgems/mruby-array-ext/src/array.c

@@ -131,7 +131,7 @@ mrb_ary_to_h(mrb_state *mrb, mrb_value ary)
 
     if (mrb_nil_p(v)) {
       mrb_raisef(mrb, E_TYPE_ERROR, "wrong element type %S at %S (expected array)",
-        mrb_str_new_cstr(mrb,  mrb_obj_classname(mrb, RARRAY_PTR(ary)[i])),
+        mrb_str_new_cstr(mrb,  mrb_obj_classname(mrb, ary_elt(ary, i))),
         mrb_fixnum_value(i)
       );
     }

mrbgems/mruby-array-ext/test/array.rb

@@ -301,6 +301,17 @@ assert('Array#to_h') do
   assert_raise(ArgumentError) { [[1]].to_h }
 end
 
+assert('Array#to_h (Modified)') do
+  class A
+    def to_ary
+      $a.clear
+      nil
+    end
+  end
+  $a = [A.new]
+  assert_raise(TypeError) { $a.to_h }
+end
+
 assert("Array#index (block)") do
   assert_nil (1..10).to_a.index { |i| i % 5 == 0 and i % 7 == 0 }
   assert_equal 34, (1..100).to_a.index { |i| i % 5 == 0 and i % 7 == 0 }

src/array.c

@@ -16,15 +16,6 @@
 #define ARY_C_MAX_SIZE (SIZE_MAX / sizeof(mrb_value))
 #define ARY_MAX_SIZE ((ARY_C_MAX_SIZE < (size_t)MRB_INT_MAX) ? (mrb_int)ARY_C_MAX_SIZE : MRB_INT_MAX-1)
 
-static inline mrb_value
-ary_elt(mrb_value ary, mrb_int offset)
-{
-  if (offset < 0 || RARRAY_LEN(ary) <= offset) {
-    return mrb_nil_value();
-  }
-  return RARRAY_PTR(ary)[offset];
-}
-
 static struct RArray*
 ary_new_capa(mrb_state *mrb, mrb_int capa)
 {