2 files changed, 17 insertions, 12 deletions
diff --git a/mrbgems/mruby-string-ext/src/string.c b/mrbgems/mruby-string-ext/src/string.c
index 4bb9b9621..6718e734a 100644
--- a/mrbgems/mruby-string-ext/src/string.c
+++ b/mrbgems/mruby-string-ext/src/string.c
@@ -107,6 +107,7 @@ mrb_str_concat2(mrb_state *mrb, mrb_value self)
  *    # returns true if one of the prefixes matches.
  *    "hello".start_with?("heaven", "hell")     #=> true
  *    "hello".start_with?("heaven", "paradise") #=> false
+ *    "h".start_with?("heaven", "hell")         #=> false
  */
 static mrb_value
 mrb_str_start_with(mrb_state *mrb, mrb_value self)
@@ -116,16 +117,17 @@ mrb_str_start_with(mrb_state *mrb, mrb_value self)
   mrb_get_args(mrb, "*", &argv, &argc);
 
   for (i = 0; i < argc; i++) {
-    size_t len_l, len_r, len_cmp;
+    size_t len_l, len_r;
     int ai = mrb_gc_arena_save(mrb);
     sub = mrb_string_type(mrb, argv[i]);
     mrb_gc_arena_restore(mrb, ai);
     len_l = RSTRING_LEN(self);
     len_r = RSTRING_LEN(sub);
-    len_cmp = (len_l > len_r) ? len_r : len_l;
-    if (memcmp(RSTRING_PTR(self), RSTRING_PTR(sub), len_cmp) == 0) {
-      return mrb_true_value();
-    }  
+    if (len_l >= len_r) {
+      if (memcmp(RSTRING_PTR(self), RSTRING_PTR(sub), len_r) == 0) {
+        return mrb_true_value();
+      }
+    }
   }
   return mrb_false_value();
 }
@@ -144,18 +146,19 @@ mrb_str_end_with(mrb_state *mrb, mrb_value self)
   mrb_get_args(mrb, "*", &argv, &argc);
 
   for (i = 0; i < argc; i++) {
-    size_t len_l, len_r, len_cmp;
+    size_t len_l, len_r;
     int ai = mrb_gc_arena_save(mrb);
     sub = mrb_string_type(mrb, argv[i]);
     mrb_gc_arena_restore(mrb, ai);
     len_l = RSTRING_LEN(self);
     len_r = RSTRING_LEN(sub);
-    len_cmp = (len_l > len_r) ? len_r : len_l;
-    if (memcmp(RSTRING_PTR(self) + (len_l - len_cmp),
-               RSTRING_PTR(sub) + (len_r - len_cmp),
-               len_cmp) == 0) {
-      return mrb_true_value();
-    }  
+    if (len_l >= len_r) {
+      if (memcmp(RSTRING_PTR(self) + (len_l - len_r),
+                 RSTRING_PTR(sub),
+                 len_r) == 0) {
+        return mrb_true_value();
+      }  
+    }
   }
   return mrb_false_value();
 }
diff --git a/mrbgems/mruby-string-ext/test/string.rb b/mrbgems/mruby-string-ext/test/string.rb
index 496730a0e..3ab959437 100644
--- a/mrbgems/mruby-string-ext/test/string.rb
+++ b/mrbgems/mruby-string-ext/test/string.rb
@@ -104,11 +104,13 @@ end
 assert('String#start_with?') do
   assert_true "hello".start_with?("heaven", "hell")
   assert_true !"hello".start_with?("heaven", "paradise")
+  assert_true !"h".start_with?("heaven", "hell")
   assert_raise TypeError do "hello".start_with?(true) end
 end
 
 assert('String#end_with?') do
   assert_true "string".end_with?("ing", "mng")
   assert_true !"string".end_with?("str", "tri")
+  assert_true !"ng".end_with?("ing", "mng")
   assert_raise TypeError do "hello".end_with?(true) end
 end