4 files changed, 29 insertions, 3 deletions
diff --git a/mrbgems/mruby-compiler/core/codegen.c b/mrbgems/mruby-compiler/core/codegen.c
index 0c84dd558..39d62348a 100644
--- a/mrbgems/mruby-compiler/core/codegen.c
+++ b/mrbgems/mruby-compiler/core/codegen.c
@@ -1798,8 +1798,10 @@ codegen(codegen_scope *s, node *tree, int val)
         int pos;
 
         pop();
-        if (val && vsp >= 0) {
-          genop(s, MKOP_AB(OP_MOVE, vsp, cursp()));
+        if (val) {
+          if (vsp >= 0) {
+            genop(s, MKOP_AB(OP_MOVE, vsp, cursp()));
+          }
           pos = genop(s, MKOP_AsBx(name[0]=='|'?OP_JMPIF:OP_JMPNOT, cursp(), 0));
         }
         else {
diff --git a/mrbgems/mruby-string-ext/src/string.c b/mrbgems/mruby-string-ext/src/string.c
index 122ee5454..dfac907ec 100644
--- a/mrbgems/mruby-string-ext/src/string.c
+++ b/mrbgems/mruby-string-ext/src/string.c
@@ -23,10 +23,11 @@ static mrb_value
 mrb_str_setbyte(mrb_state *mrb, mrb_value str)
 {
   mrb_int pos, byte;
-  long len = RSTRING_LEN(str);
+  long len;
 
   mrb_get_args(mrb, "ii", &pos, &byte);
 
+  len = RSTRING_LEN(str);
   if (pos < -len || len <= pos)
     mrb_raisef(mrb, E_INDEX_ERROR, "index %S is out of array", mrb_fixnum_value(pos));
   if (pos < 0)
diff --git a/mrbgems/mruby-string-ext/test/string.rb b/mrbgems/mruby-string-ext/test/string.rb
index a5d55a7ee..228a236af 100644
--- a/mrbgems/mruby-string-ext/test/string.rb
+++ b/mrbgems/mruby-string-ext/test/string.rb
@@ -30,6 +30,18 @@ assert('String#setbyte') do
   assert_equal("Hello", str1)
 end
 
+assert("String#setbyte raises IndexError if arg conversion resizes String") do
+  $s = "01234\n"
+  class Tmp
+      def to_i
+          $s.chomp! ''
+          95
+      end
+  end
+  tmp = Tmp.new
+  assert_raise(IndexError) { $s.setbyte(5, tmp) }
+end
+
 assert('String#byteslice') do
   str1 = "hello"
   assert_equal("e", str1.byteslice(1))
diff --git a/test/t/codegen.rb b/test/t/codegen.rb
new file mode 100644
index 000000000..f910d37fb
--- /dev/null
+++ b/test/t/codegen.rb
@@ -0,0 +1,11 @@
+##
+# Codegen tests
+
+assert('peephole optimization does not eliminate move whose result is reused') do
+  assert_raise LocalJumpError do
+    def method
+      yield
+    end
+    method(&a &&= 0)
+  end
+end