diff --git a/ruby/ext/google/protobuf_c/defs.c b/ruby/ext/google/protobuf_c/defs.c
index 8f9f33e..a5ca1ba 100644
--- a/ruby/ext/google/protobuf_c/defs.c
+++ b/ruby/ext/google/protobuf_c/defs.c
@@ -88,7 +88,7 @@
     }                                                               \
 
 #define DEFINE_SELF(type, var, rb_var)                              \
-    type* var = ruby_to_ ## type(rb_var);
+    type* var = ruby_to_ ## type(rb_var)
 
 // Global singleton DescriptorPool. The user is free to create others, but this
 // is used by generated code.
@@ -656,13 +656,13 @@
 VALUE FieldDescriptor_label_set(VALUE _self, VALUE label) {
   DEFINE_SELF(FieldDescriptor, self, _self);
   upb_fielddef* mut_def = check_field_notfrozen(self->fielddef);
+  upb_label_t upb_label = -1;
+  bool converted = false;
+
   if (TYPE(label) != T_SYMBOL) {
     rb_raise(rb_eArgError, "Expected symbol for field label.");
   }
 
-  upb_label_t upb_label = -1;
-  bool converted = false;
-
 #define CONVERT(upb, ruby)                                           \
   if (SYM2ID(label) == rb_intern( # ruby )) {                        \
     upb_label = UPB_LABEL_ ## upb;                                   \
@@ -740,10 +740,10 @@
 VALUE FieldDescriptor_submsg_name_set(VALUE _self, VALUE value) {
   DEFINE_SELF(FieldDescriptor, self, _self);
   upb_fielddef* mut_def = check_field_notfrozen(self->fielddef);
+  const char* str = get_str(value);
   if (!upb_fielddef_hassubdef(self->fielddef)) {
     rb_raise(rb_eTypeError, "FieldDescriptor does not have subdef.");
   }
-  const char* str = get_str(value);
   CHECK_UPB(upb_fielddef_setsubdefname(mut_def, str, &status),
             "Error setting submessage name");
   return Qnil;
@@ -760,10 +760,12 @@
  */
 VALUE FieldDescriptor_subtype(VALUE _self) {
   DEFINE_SELF(FieldDescriptor, self, _self);
+  const upb_def* def;
+
   if (!upb_fielddef_hassubdef(self->fielddef)) {
     return Qnil;
   }
-  const upb_def* def = upb_fielddef_subdef(self->fielddef);
+  def = upb_fielddef_subdef(self->fielddef);
   if (def == NULL) {
     return Qnil;
   }
@@ -1187,14 +1189,15 @@
  */
 VALUE MessageBuilderContext_optional(int argc, VALUE* argv, VALUE _self) {
   DEFINE_SELF(MessageBuilderContext, self, _self);
+  VALUE name, type, number, type_class;
 
   if (argc < 3) {
     rb_raise(rb_eArgError, "Expected at least 3 arguments.");
   }
-  VALUE name = argv[0];
-  VALUE type = argv[1];
-  VALUE number = argv[2];
-  VALUE type_class = (argc > 3) ? argv[3] : Qnil;
+  name = argv[0];
+  type = argv[1];
+  number = argv[2];
+  type_class = (argc > 3) ? argv[3] : Qnil;
 
   return msgdef_add_field(self->descriptor, "optional",
                           name, type, number, type_class);
@@ -1215,14 +1218,15 @@
  */
 VALUE MessageBuilderContext_required(int argc, VALUE* argv, VALUE _self) {
   DEFINE_SELF(MessageBuilderContext, self, _self);
+  VALUE name, type, number, type_class;
 
   if (argc < 3) {
     rb_raise(rb_eArgError, "Expected at least 3 arguments.");
   }
-  VALUE name = argv[0];
-  VALUE type = argv[1];
-  VALUE number = argv[2];
-  VALUE type_class = (argc > 3) ? argv[3] : Qnil;
+  name = argv[0];
+  type = argv[1];
+  number = argv[2];
+  type_class = (argc > 3) ? argv[3] : Qnil;
 
   return msgdef_add_field(self->descriptor, "required",
                           name, type, number, type_class);
@@ -1239,14 +1243,15 @@
  */
 VALUE MessageBuilderContext_repeated(int argc, VALUE* argv, VALUE _self) {
   DEFINE_SELF(MessageBuilderContext, self, _self);
+  VALUE name, type, number, type_class;
 
   if (argc < 3) {
     rb_raise(rb_eArgError, "Expected at least 3 arguments.");
   }
-  VALUE name = argv[0];
-  VALUE type = argv[1];
-  VALUE number = argv[2];
-  VALUE type_class = (argc > 3) ? argv[3] : Qnil;
+  name = argv[0];
+  type = argv[1];
+  number = argv[2];
+  type_class = (argc > 3) ? argv[3] : Qnil;
 
   return msgdef_add_field(self->descriptor, "repeated",
                           name, type, number, type_class);
@@ -1266,15 +1271,17 @@
  */
 VALUE MessageBuilderContext_map(int argc, VALUE* argv, VALUE _self) {
   DEFINE_SELF(MessageBuilderContext, self, _self);
+  VALUE name, key_type, value_type, number, type_class;
+  VALUE mapentry_desc, mapentry_desc_name;
 
   if (argc < 4) {
     rb_raise(rb_eArgError, "Expected at least 4 arguments.");
   }
-  VALUE name = argv[0];
-  VALUE key_type = argv[1];
-  VALUE value_type = argv[2];
-  VALUE number = argv[3];
-  VALUE type_class = (argc > 4) ? argv[4] : Qnil;
+  name = argv[0];
+  key_type = argv[1];
+  value_type = argv[2];
+  number = argv[3];
+  type_class = (argc > 4) ? argv[4] : Qnil;
 
   // Validate the key type. We can't accept enums, messages, or floats/doubles
   // as map keys. (We exclude these explicitly, and the field-descriptor setter
@@ -1290,55 +1297,67 @@
 
   // Create a new message descriptor for the map entry message, and create a
   // repeated submessage field here with that type.
-  VALUE mapentry_desc = rb_class_new_instance(0, NULL, cDescriptor);
-  VALUE mapentry_desc_name = rb_funcall(self->descriptor, rb_intern("name"), 0);
+  mapentry_desc = rb_class_new_instance(0, NULL, cDescriptor);
+  mapentry_desc_name = rb_funcall(self->descriptor, rb_intern("name"), 0);
   mapentry_desc_name = rb_str_cat2(mapentry_desc_name, "_MapEntry_");
   mapentry_desc_name = rb_str_cat2(mapentry_desc_name,
                                    rb_id2name(SYM2ID(name)));
   Descriptor_name_set(mapentry_desc, mapentry_desc_name);
 
-  // The 'mapentry' attribute has no Ruby setter because we do not want the user
-  // attempting to DIY the setup below; we want to ensure that the fields are
-  // correct. So we reach into the msgdef here to set the bit manually.
-  Descriptor* mapentry_desc_self = ruby_to_Descriptor(mapentry_desc);
-  upb_msgdef_setmapentry((upb_msgdef*)mapentry_desc_self->msgdef, true);
-
-  // optional <type> key = 1;
-  VALUE key_field = rb_class_new_instance(0, NULL, cFieldDescriptor);
-  FieldDescriptor_name_set(key_field, rb_str_new2("key"));
-  FieldDescriptor_label_set(key_field, ID2SYM(rb_intern("optional")));
-  FieldDescriptor_number_set(key_field, INT2NUM(1));
-  FieldDescriptor_type_set(key_field, key_type);
-  Descriptor_add_field(mapentry_desc, key_field);
-
-  // optional <type> value = 2;
-  VALUE value_field = rb_class_new_instance(0, NULL, cFieldDescriptor);
-  FieldDescriptor_name_set(value_field, rb_str_new2("value"));
-  FieldDescriptor_label_set(value_field, ID2SYM(rb_intern("optional")));
-  FieldDescriptor_number_set(value_field, INT2NUM(2));
-  FieldDescriptor_type_set(value_field, value_type);
-  if (type_class != Qnil) {
-    VALUE submsg_name = rb_str_new2("."); // prepend '.' to make name absolute.
-    submsg_name = rb_str_append(submsg_name, type_class);
-    FieldDescriptor_submsg_name_set(value_field, submsg_name);
+  {
+    // The 'mapentry' attribute has no Ruby setter because we do not want the
+    // user attempting to DIY the setup below; we want to ensure that the fields
+    // are correct. So we reach into the msgdef here to set the bit manually.
+    Descriptor* mapentry_desc_self = ruby_to_Descriptor(mapentry_desc);
+    upb_msgdef_setmapentry((upb_msgdef*)mapentry_desc_self->msgdef, true);
   }
-  Descriptor_add_field(mapentry_desc, value_field);
 
-  // Add the map-entry message type to the current builder, and use the type to
-  // create the map field itself.
-  Builder* builder_self = ruby_to_Builder(self->builder);
-  rb_ary_push(builder_self->pending_list, mapentry_desc);
+  {
+    // optional <type> key = 1;
+    VALUE key_field = rb_class_new_instance(0, NULL, cFieldDescriptor);
+    FieldDescriptor_name_set(key_field, rb_str_new2("key"));
+    FieldDescriptor_label_set(key_field, ID2SYM(rb_intern("optional")));
+    FieldDescriptor_number_set(key_field, INT2NUM(1));
+    FieldDescriptor_type_set(key_field, key_type);
+    Descriptor_add_field(mapentry_desc, key_field);
+  }
 
-  VALUE map_field = rb_class_new_instance(0, NULL, cFieldDescriptor);
-  VALUE name_str = rb_str_new2(rb_id2name(SYM2ID(name)));
-  FieldDescriptor_name_set(map_field, name_str);
-  FieldDescriptor_number_set(map_field, number);
-  FieldDescriptor_label_set(map_field, ID2SYM(rb_intern("repeated")));
-  FieldDescriptor_type_set(map_field, ID2SYM(rb_intern("message")));
-  VALUE submsg_name = rb_str_new2("."); // prepend '.' to make name absolute.
-  submsg_name = rb_str_append(submsg_name, mapentry_desc_name);
-  FieldDescriptor_submsg_name_set(map_field, submsg_name);
-  Descriptor_add_field(self->descriptor, map_field);
+  {
+    // optional <type> value = 2;
+    VALUE value_field = rb_class_new_instance(0, NULL, cFieldDescriptor);
+    FieldDescriptor_name_set(value_field, rb_str_new2("value"));
+    FieldDescriptor_label_set(value_field, ID2SYM(rb_intern("optional")));
+    FieldDescriptor_number_set(value_field, INT2NUM(2));
+    FieldDescriptor_type_set(value_field, value_type);
+    if (type_class != Qnil) {
+      VALUE submsg_name = rb_str_new2("."); // prepend '.' to make absolute.
+      submsg_name = rb_str_append(submsg_name, type_class);
+      FieldDescriptor_submsg_name_set(value_field, submsg_name);
+    }
+    Descriptor_add_field(mapentry_desc, value_field);
+  }
+
+  {
+    // Add the map-entry message type to the current builder, and use the type
+    // to create the map field itself.
+    Builder* builder_self = ruby_to_Builder(self->builder);
+    rb_ary_push(builder_self->pending_list, mapentry_desc);
+  }
+
+  {
+    VALUE map_field = rb_class_new_instance(0, NULL, cFieldDescriptor);
+    VALUE name_str = rb_str_new2(rb_id2name(SYM2ID(name)));
+    VALUE submsg_name;
+
+    FieldDescriptor_name_set(map_field, name_str);
+    FieldDescriptor_number_set(map_field, number);
+    FieldDescriptor_label_set(map_field, ID2SYM(rb_intern("repeated")));
+    FieldDescriptor_type_set(map_field, ID2SYM(rb_intern("message")));
+    submsg_name = rb_str_new2("."); // prepend '.' to make name absolute.
+    submsg_name = rb_str_append(submsg_name, mapentry_desc_name);
+    FieldDescriptor_submsg_name_set(map_field, submsg_name);
+    Descriptor_add_field(self->descriptor, map_field);
+  }
 
   return Qnil;
 }
@@ -1434,14 +1453,15 @@
  */
 VALUE OneofBuilderContext_optional(int argc, VALUE* argv, VALUE _self) {
   DEFINE_SELF(OneofBuilderContext, self, _self);
+  VALUE name, type, number, type_class;
 
   if (argc < 3) {
     rb_raise(rb_eArgError, "Expected at least 3 arguments.");
   }
-  VALUE name = argv[0];
-  VALUE type = argv[1];
-  VALUE number = argv[2];
-  VALUE type_class = (argc > 3) ? argv[3] : Qnil;
+  name = argv[0];
+  type = argv[1];
+  number = argv[2];
+  type_class = (argc > 3) ? argv[3] : Qnil;
 
   return msgdef_add_field(self->descriptor, "optional",
                           name, type, number, type_class);
diff --git a/ruby/ext/google/protobuf_c/encode_decode.c b/ruby/ext/google/protobuf_c/encode_decode.c
index fe249d4..68f3b75 100644
--- a/ruby/ext/google/protobuf_c/encode_decode.c
+++ b/ruby/ext/google/protobuf_c/encode_decode.c
@@ -175,11 +175,11 @@
   VALUE subdesc =
       get_def_obj((void*)submsgdata->md);
   VALUE subklass = Descriptor_msgclass(subdesc);
+  MessageHeader* submsg;
 
   VALUE submsg_rb = rb_class_new_instance(0, NULL, subklass);
   RepeatedField_push(ary, submsg_rb);
 
-  MessageHeader* submsg;
   TypedData_Get_Struct(submsg_rb, MessageHeader, &Message_type, submsg);
   return submsg;
 }
@@ -191,14 +191,15 @@
   VALUE subdesc =
       get_def_obj((void*)submsgdata->md);
   VALUE subklass = Descriptor_msgclass(subdesc);
+  VALUE submsg_rb;
+  MessageHeader* submsg;
 
   if (DEREF(msg, submsgdata->ofs, VALUE) == Qnil) {
     DEREF(msg, submsgdata->ofs, VALUE) =
         rb_class_new_instance(0, NULL, subklass);
   }
 
-  VALUE submsg_rb = DEREF(msg, submsgdata->ofs, VALUE);
-  MessageHeader* submsg;
+  submsg_rb = DEREF(msg, submsgdata->ofs, VALUE);
   TypedData_Get_Struct(submsg_rb, MessageHeader, &Message_type, submsg);
   return submsg;
 }
@@ -254,12 +255,14 @@
       &frame->key_storage);
 
   VALUE value_field_typeclass = Qnil;
+  VALUE value;
+
   if (mapdata->value_field_type == UPB_TYPE_MESSAGE ||
       mapdata->value_field_type == UPB_TYPE_ENUM) {
     value_field_typeclass = get_def_obj(mapdata->value_field_subdef);
   }
 
-  VALUE value = native_slot_get(
+  value = native_slot_get(
       mapdata->value_field_type, value_field_typeclass,
       &frame->value_storage);
 
@@ -280,15 +283,14 @@
     size_t ofs,
     const upb_msgdef* mapentry_def,
     Descriptor* desc) {
-
+  const upb_fielddef* key_field;
+  const upb_fielddef* value_field;
   map_handlerdata_t* hd = ALLOC(map_handlerdata_t);
   hd->ofs = ofs;
-  const upb_fielddef* key_field = upb_msgdef_itof(mapentry_def,
-                                                  MAP_KEY_FIELD);
+  key_field = upb_msgdef_itof(mapentry_def, MAP_KEY_FIELD);
   assert(key_field != NULL);
   hd->key_field_type = upb_fielddef_type(key_field);
-  const upb_fielddef* value_field = upb_msgdef_itof(mapentry_def,
-                                                    MAP_VALUE_FIELD);
+  value_field = upb_msgdef_itof(mapentry_def, MAP_VALUE_FIELD);
   assert(value_field != NULL);
   hd->value_field_type = upb_fielddef_type(value_field);
   hd->value_field_subdef = upb_fielddef_subdef(value_field);
@@ -354,6 +356,8 @@
   VALUE subdesc =
       get_def_obj((void*)oneofdata->md);
   VALUE subklass = Descriptor_msgclass(subdesc);
+  VALUE submsg_rb;
+  MessageHeader* submsg;
 
   if (oldcase != oneofdata->oneof_case_num ||
       DEREF(msg, oneofdata->ofs, VALUE) == Qnil) {
@@ -369,8 +373,7 @@
   DEREF(msg, oneofdata->case_ofs, uint32_t) =
       oneofdata->oneof_case_num;
 
-  VALUE submsg_rb = DEREF(msg, oneofdata->ofs, VALUE);
-  MessageHeader* submsg;
+  submsg_rb = DEREF(msg, oneofdata->ofs, VALUE);
   TypedData_Get_Struct(submsg_rb, MessageHeader, &Message_type, submsg);
   return submsg;
 }
@@ -465,8 +468,9 @@
                                       Descriptor* desc) {
   const upb_msgdef* map_msgdef = upb_fielddef_msgsubdef(fielddef);
   map_handlerdata_t* hd = new_map_handlerdata(offset, map_msgdef, desc);
-  upb_handlers_addcleanup(h, hd, free);
   upb_handlerattr attr = UPB_HANDLERATTR_INITIALIZER;
+
+  upb_handlers_addcleanup(h, hd, free);
   upb_handlerattr_sethandlerdata(&attr, hd);
   upb_handlers_setstartsubmsg(h, fielddef, startmapentry_handler, &attr);
   upb_handlerattr_uninit(&attr);
@@ -479,8 +483,9 @@
   const upb_fielddef* key_field = map_entry_key(msgdef);
   const upb_fielddef* value_field = map_entry_value(msgdef);
   map_handlerdata_t* hd = new_map_handlerdata(0, msgdef, desc);
-  upb_handlers_addcleanup(h, hd, free);
   upb_handlerattr attr = UPB_HANDLERATTR_INITIALIZER;
+
+  upb_handlers_addcleanup(h, hd, free);
   upb_handlerattr_sethandlerdata(&attr, hd);
   upb_handlers_setendmsg(h, endmap_handler, &attr);
 
@@ -542,6 +547,7 @@
 static void add_handlers_for_message(const void *closure, upb_handlers *h) {
   const upb_msgdef* msgdef = upb_handlers_msgdef(h);
   Descriptor* desc = ruby_to_Descriptor(get_def_obj((void*)msgdef));
+  upb_msg_field_iter i;
 
   // If this is a mapentry message type, set up a special set of handlers and
   // bail out of the normal (user-defined) message type handling.
@@ -558,7 +564,6 @@
     desc->layout = create_layout(desc->msgdef);
   }
 
-  upb_msg_field_iter i;
   for (upb_msg_field_begin(&i, desc->msgdef);
        !upb_msg_field_done(&i);
        upb_msg_field_next(&i)) {
@@ -610,8 +615,7 @@
   upb_pbdecodermethodopts opts;
   upb_pbdecodermethodopts_init(&opts, handlers);
 
-  const upb_pbdecodermethod *ret = upb_pbdecodermethod_new(&opts, owner);
-  return ret;
+  return upb_pbdecodermethod_new(&opts, owner);
 }
 
 static const upb_pbdecodermethod *msgdef_decodermethod(Descriptor* desc) {
@@ -677,28 +681,31 @@
   VALUE descriptor = rb_ivar_get(klass, descriptor_instancevar_interned);
   Descriptor* desc = ruby_to_Descriptor(descriptor);
   VALUE msgklass = Descriptor_msgclass(descriptor);
+  VALUE msg_rb;
+  MessageHeader* msg;
 
   if (TYPE(data) != T_STRING) {
     rb_raise(rb_eArgError, "Expected string for binary protobuf data.");
   }
 
-  VALUE msg_rb = rb_class_new_instance(0, NULL, msgklass);
-  MessageHeader* msg;
+  msg_rb = rb_class_new_instance(0, NULL, msgklass);
   TypedData_Get_Struct(msg_rb, MessageHeader, &Message_type, msg);
 
-  const upb_pbdecodermethod* method = msgdef_decodermethod(desc);
-  const upb_handlers* h = upb_pbdecodermethod_desthandlers(method);
-  stackenv se;
-  stackenv_init(&se, "Error occurred during parsing: %s");
+  {
+    const upb_pbdecodermethod* method = msgdef_decodermethod(desc);
+    const upb_handlers* h = upb_pbdecodermethod_desthandlers(method);
+    stackenv se;
+    upb_sink sink;
+    upb_pbdecoder* decoder;
+    stackenv_init(&se, "Error occurred during parsing: %s");
 
-  upb_sink sink;
-  upb_sink_reset(&sink, h, msg);
-  upb_pbdecoder* decoder =
-      upb_pbdecoder_create(&se.env, method, &sink);
-  upb_bufsrc_putbuf(RSTRING_PTR(data), RSTRING_LEN(data),
-                    upb_pbdecoder_input(decoder));
+    upb_sink_reset(&sink, h, msg);
+    decoder = upb_pbdecoder_create(&se.env, method, &sink);
+    upb_bufsrc_putbuf(RSTRING_PTR(data), RSTRING_LEN(data),
+                      upb_pbdecoder_input(decoder));
 
-  stackenv_uninit(&se);
+    stackenv_uninit(&se);
+  }
 
   return msg_rb;
 }
@@ -715,6 +722,8 @@
   VALUE descriptor = rb_ivar_get(klass, descriptor_instancevar_interned);
   Descriptor* desc = ruby_to_Descriptor(descriptor);
   VALUE msgklass = Descriptor_msgclass(descriptor);
+  VALUE msg_rb;
+  MessageHeader* msg;
 
   if (TYPE(data) != T_STRING) {
     rb_raise(rb_eArgError, "Expected string for JSON data.");
@@ -723,20 +732,22 @@
   // convert, because string handlers pass data directly to message string
   // fields.
 
-  VALUE msg_rb = rb_class_new_instance(0, NULL, msgklass);
-  MessageHeader* msg;
+  msg_rb = rb_class_new_instance(0, NULL, msgklass);
   TypedData_Get_Struct(msg_rb, MessageHeader, &Message_type, msg);
 
-  stackenv se;
-  stackenv_init(&se, "Error occurred during parsing: %s");
+  {
+    stackenv se;
+    upb_sink sink;
+    upb_json_parser* parser;
+    stackenv_init(&se, "Error occurred during parsing: %s");
 
-  upb_sink sink;
-  upb_sink_reset(&sink, get_fill_handlers(desc), msg);
-  upb_json_parser* parser = upb_json_parser_create(&se.env, &sink);
-  upb_bufsrc_putbuf(RSTRING_PTR(data), RSTRING_LEN(data),
-                    upb_json_parser_input(parser));
+    upb_sink_reset(&sink, get_fill_handlers(desc), msg);
+    parser = upb_json_parser_create(&se.env, &sink);
+    upb_bufsrc_putbuf(RSTRING_PTR(data), RSTRING_LEN(data),
+                      upb_json_parser_input(parser));
 
-  stackenv_uninit(&se);
+    stackenv_uninit(&se);
+  }
 
   return msg_rb;
 }
@@ -767,12 +778,12 @@
 
 static size_t stringsink_string(void *_sink, const void *hd, const char *ptr,
                                 size_t len, const upb_bufhandle *handle) {
-  UPB_UNUSED(hd);
-  UPB_UNUSED(handle);
-
   stringsink *sink = _sink;
   size_t new_size = sink->size;
 
+  UPB_UNUSED(hd);
+  UPB_UNUSED(handle);
+
   while (sink->len + len > new_size) {
     new_size *= 2;
   }
@@ -826,10 +837,11 @@
 }
 
 static void putstr(VALUE str, const upb_fielddef *f, upb_sink *sink) {
+  upb_sink subsink;
+
   if (str == Qnil) return;
 
   assert(BUILTIN_TYPE(str) == RUBY_T_STRING);
-  upb_sink subsink;
 
   // Ensure that the string has the correct encoding. We also check at field-set
   // time, but the user may have mutated the string object since then.
@@ -844,11 +856,14 @@
 
 static void putsubmsg(VALUE submsg, const upb_fielddef *f, upb_sink *sink,
                       int depth) {
+  upb_sink subsink;
+  VALUE descriptor;
+  Descriptor* subdesc;
+
   if (submsg == Qnil) return;
 
-  upb_sink subsink;
-  VALUE descriptor = rb_ivar_get(submsg, descriptor_instancevar_interned);
-  Descriptor* subdesc = ruby_to_Descriptor(descriptor);
+  descriptor = rb_ivar_get(submsg, descriptor_instancevar_interned);
+  subdesc = ruby_to_Descriptor(descriptor);
 
   upb_sink_startsubmsg(sink, getsel(f, UPB_HANDLER_STARTSUBMSG), &subsink);
   putmsg(submsg, subdesc, &subsink, depth + 1);
@@ -857,19 +872,20 @@
 
 static void putary(VALUE ary, const upb_fielddef *f, upb_sink *sink,
                    int depth) {
-  if (ary == Qnil) return;
-
   upb_sink subsink;
+  upb_fieldtype_t type = upb_fielddef_type(f);
+  upb_selector_t sel = 0;
+  int size;
+
+  if (ary == Qnil) return;
 
   upb_sink_startseq(sink, getsel(f, UPB_HANDLER_STARTSEQ), &subsink);
 
-  upb_fieldtype_t type = upb_fielddef_type(f);
-  upb_selector_t sel = 0;
   if (upb_fielddef_isprimitive(f)) {
     sel = getsel(f, upb_handlers_getprimitivehandlertype(f));
   }
 
-  int size = NUM2INT(RepeatedField_length(ary));
+  size = NUM2INT(RepeatedField_length(ary));
   for (int i = 0; i < size; i++) {
     void* memory = RepeatedField_index_native(ary, i);
     switch (type) {
@@ -952,21 +968,25 @@
 
 static void putmap(VALUE map, const upb_fielddef *f, upb_sink *sink,
                    int depth) {
-  if (map == Qnil) return;
-  Map* self = ruby_to_Map(map);
-
+  Map* self;
   upb_sink subsink;
+  const upb_fielddef* key_field;
+  const upb_fielddef* value_field;
+  Map_iter it;
+
+  if (map == Qnil) return;
+  self = ruby_to_Map(map);
 
   upb_sink_startseq(sink, getsel(f, UPB_HANDLER_STARTSEQ), &subsink);
 
   assert(upb_fielddef_type(f) == UPB_TYPE_MESSAGE);
-  const upb_fielddef* key_field = map_field_key(f);
-  const upb_fielddef* value_field = map_field_value(f);
+  key_field = map_field_key(f);
+  value_field = map_field_value(f);
 
-  Map_iter it;
   for (Map_begin(map, &it); !Map_done(&it); Map_next(&it)) {
     VALUE key = Map_iter_key(&it);
     VALUE value = Map_iter_value(&it);
+    upb_status status;
 
     upb_sink entry_sink;
     upb_sink_startsubmsg(&subsink, getsel(f, UPB_HANDLER_STARTSUBMSG),
@@ -977,7 +997,6 @@
     put_ruby_value(value, value_field, self->value_type_class, depth + 1,
                    &entry_sink);
 
-    upb_status status;
     upb_sink_endmsg(&entry_sink, &status);
     upb_sink_endsubmsg(&subsink, getsel(f, UPB_HANDLER_ENDSUBMSG));
   }
@@ -987,6 +1006,10 @@
 
 static void putmsg(VALUE msg_rb, const Descriptor* desc,
                    upb_sink *sink, int depth) {
+  MessageHeader* msg;
+  upb_msg_field_iter i;
+  upb_status status;
+
   upb_sink_startmsg(sink);
 
   // Protect against cycles (possible because users may freely reassign message
@@ -996,10 +1019,8 @@
              "Maximum recursion depth exceeded during encoding.");
   }
 
-  MessageHeader* msg;
   TypedData_Get_Struct(msg_rb, MessageHeader, &Message_type, msg);
 
-  upb_msg_field_iter i;
   for (upb_msg_field_begin(&i, desc->msgdef);
        !upb_msg_field_done(&i);
        upb_msg_field_next(&i)) {
@@ -1071,7 +1092,6 @@
     }
   }
 
-  upb_status status;
   upb_sink_endmsg(sink, &status);
 }
 
@@ -1106,22 +1126,26 @@
   stringsink sink;
   stringsink_init(&sink);
 
-  const upb_handlers* serialize_handlers =
-      msgdef_pb_serialize_handlers(desc);
+  {
+    const upb_handlers* serialize_handlers =
+        msgdef_pb_serialize_handlers(desc);
 
-  stackenv se;
-  stackenv_init(&se, "Error occurred during encoding: %s");
-  upb_pb_encoder* encoder =
-      upb_pb_encoder_create(&se.env, serialize_handlers, &sink.sink);
+    stackenv se;
+    upb_pb_encoder* encoder;
+    VALUE ret;
 
-  putmsg(msg_rb, desc, upb_pb_encoder_input(encoder), 0);
+    stackenv_init(&se, "Error occurred during encoding: %s");
+    encoder = upb_pb_encoder_create(&se.env, serialize_handlers, &sink.sink);
 
-  VALUE ret = rb_str_new(sink.ptr, sink.len);
+    putmsg(msg_rb, desc, upb_pb_encoder_input(encoder), 0);
 
-  stackenv_uninit(&se);
-  stringsink_uninit(&sink);
+    ret = rb_str_new(sink.ptr, sink.len);
 
-  return ret;
+    stackenv_uninit(&se);
+    stringsink_uninit(&sink);
+
+    return ret;
+  }
 }
 
 /*
@@ -1137,21 +1161,24 @@
   stringsink sink;
   stringsink_init(&sink);
 
-  const upb_handlers* serialize_handlers =
-      msgdef_json_serialize_handlers(desc);
+  {
+    const upb_handlers* serialize_handlers =
+        msgdef_json_serialize_handlers(desc);
+    upb_json_printer* printer;
+    stackenv se;
+    VALUE ret;
 
-  stackenv se;
-  stackenv_init(&se, "Error occurred during encoding: %s");
-  upb_json_printer* printer =
-      upb_json_printer_create(&se.env, serialize_handlers, &sink.sink);
+    stackenv_init(&se, "Error occurred during encoding: %s");
+    printer = upb_json_printer_create(&se.env, serialize_handlers, &sink.sink);
 
-  putmsg(msg_rb, desc, upb_json_printer_input(printer), 0);
+    putmsg(msg_rb, desc, upb_json_printer_input(printer), 0);
 
-  VALUE ret = rb_str_new(sink.ptr, sink.len);
+    ret = rb_str_new(sink.ptr, sink.len);
 
-  stackenv_uninit(&se);
-  stringsink_uninit(&sink);
+    stackenv_uninit(&se);
+    stringsink_uninit(&sink);
 
-  return ret;
+    return ret;
+  }
 }
 
diff --git a/ruby/ext/google/protobuf_c/map.c b/ruby/ext/google/protobuf_c/map.c
index 3436e09..5043f39 100644
--- a/ruby/ext/google/protobuf_c/map.c
+++ b/ruby/ext/google/protobuf_c/map.c
@@ -167,9 +167,9 @@
 
 VALUE Map_alloc(VALUE klass) {
   Map* self = ALLOC(Map);
+  VALUE ret = TypedData_Wrap_Struct(klass, &Map_type, self);
   memset(self, 0, sizeof(Map));
   self->value_type_class = Qnil;
-  VALUE ret = TypedData_Wrap_Struct(klass, &Map_type, self);
   return ret;
 }
 
@@ -215,6 +215,7 @@
  */
 VALUE Map_init(int argc, VALUE* argv, VALUE _self) {
   Map* self = ruby_to_Map(_self);
+  int init_value_arg;
 
   // We take either two args (:key_type, :value_type), three args (:key_type,
   // :value_type, "ValueMessageType"), or four args (the above plus an initial
@@ -241,7 +242,7 @@
       rb_raise(rb_eArgError, "Invalid key type for map.");
   }
 
-  int init_value_arg = 2;
+  init_value_arg = 2;
   if (needs_typeclass(self->value_type) && argc > 2) {
     self->value_type_class = argv[2];
     validate_type_class(self->value_type, self->value_type_class);
@@ -356,9 +357,9 @@
   char keybuf[TABLE_KEY_BUF_LENGTH];
   const char* keyval = NULL;
   size_t length = 0;
+  upb_value v;
   table_key(self, key, keybuf, &keyval, &length);
 
-  upb_value v;
   if (upb_strtable_lookup2(&self->table, keyval, length, &v)) {
     void* mem = value_memory(&v);
     return native_slot_get(self->value_type, self->value_type_class, mem);
@@ -381,10 +382,11 @@
   char keybuf[TABLE_KEY_BUF_LENGTH];
   const char* keyval = NULL;
   size_t length = 0;
+  upb_value v;
+  void* mem;
   table_key(self, key, keybuf, &keyval, &length);
 
-  upb_value v;
-  void* mem = value_memory(&v);
+  mem = value_memory(&v);
   native_slot_set(self->value_type, self->value_type_class, mem, value);
 
   // Replace any existing value by issuing a 'remove' operation first.
@@ -432,9 +434,9 @@
   char keybuf[TABLE_KEY_BUF_LENGTH];
   const char* keyval = NULL;
   size_t length = 0;
+  upb_value v;
   table_key(self, key, keybuf, &keyval, &length);
 
-  upb_value v;
   if (upb_strtable_remove2(&self->table, keyval, length, &v)) {
     void* mem = value_memory(&v);
     return native_slot_get(self->value_type, self->value_type_class, mem);
@@ -564,6 +566,8 @@
  */
 VALUE Map_eq(VALUE _self, VALUE _other) {
   Map* self = ruby_to_Map(_self);
+  Map* other;
+  upb_strtable_iter it;
 
   // Allow comparisons to Ruby hashmaps by converting to a temporary Map
   // instance. Slow, but workable.
@@ -573,7 +577,7 @@
     _other = other_map;
   }
 
-  Map* other = ruby_to_Map(_other);
+  other = ruby_to_Map(_other);
 
   if (self == other) {
     return Qtrue;
@@ -589,7 +593,6 @@
 
   // For each member of self, check that an equal member exists at the same key
   // in other.
-  upb_strtable_iter it;
   for (upb_strtable_begin(&it, &self->table);
        !upb_strtable_done(&it);
        upb_strtable_next(&it)) {
@@ -719,6 +722,7 @@
 
     Map* self = ruby_to_Map(_self);
     Map* other = ruby_to_Map(hashmap);
+    upb_strtable_iter it;
 
     if (self->key_type != other->key_type ||
         self->value_type != other->value_type ||
@@ -726,19 +730,19 @@
       rb_raise(rb_eArgError, "Attempt to merge Map with mismatching types");
     }
 
-    upb_strtable_iter it;
     for (upb_strtable_begin(&it, &other->table);
          !upb_strtable_done(&it);
          upb_strtable_next(&it)) {
 
       // Replace any existing value by issuing a 'remove' operation first.
+      upb_value v;
       upb_value oldv;
       upb_strtable_remove2(&self->table,
                            upb_strtable_iter_key(&it),
                            upb_strtable_iter_keylength(&it),
                            &oldv);
 
-      upb_value v = upb_strtable_iter_value(&it);
+      v = upb_strtable_iter_value(&it);
       upb_strtable_insert2(&self->table,
                            upb_strtable_iter_key(&it),
                            upb_strtable_iter_keylength(&it),
diff --git a/ruby/ext/google/protobuf_c/message.c b/ruby/ext/google/protobuf_c/message.c
index 4be1c8c..ebe2f1a 100644
--- a/ruby/ext/google/protobuf_c/message.c
+++ b/ruby/ext/google/protobuf_c/message.c
@@ -57,11 +57,13 @@
   Descriptor* desc = ruby_to_Descriptor(descriptor);
   MessageHeader* msg = (MessageHeader*)ALLOC_N(
       uint8_t, sizeof(MessageHeader) + desc->layout->size);
+  VALUE ret;
+
   memset(Message_data(msg), 0, desc->layout->size);
 
   // We wrap first so that everything in the message object is GC-rooted in case
   // a collection happens during object creation in layout_init().
-  VALUE ret = TypedData_Wrap_Struct(klass, &Message_type, msg);
+  ret = TypedData_Wrap_Struct(klass, &Message_type, msg);
   msg->descriptor = desc;
   rb_ivar_set(ret, descriptor_instancevar_interned, descriptor);
 
@@ -71,29 +73,34 @@
 }
 
 static VALUE which_oneof_field(MessageHeader* self, const upb_oneofdef* o) {
+  upb_oneof_iter it;
+  size_t case_ofs;
+  uint32_t oneof_case;
+  const upb_fielddef* first_field;
+  const upb_fielddef* f;
+
   // If no fields in the oneof, always nil.
   if (upb_oneofdef_numfields(o) == 0) {
     return Qnil;
   }
   // Grab the first field in the oneof so we can get its layout info to find the
   // oneof_case field.
-  upb_oneof_iter it;
   upb_oneof_begin(&it, o);
   assert(!upb_oneof_done(&it));
-  const upb_fielddef* first_field = upb_oneof_iter_field(&it);
+  first_field = upb_oneof_iter_field(&it);
   assert(upb_fielddef_containingoneof(first_field) != NULL);
 
-  size_t case_ofs =
+  case_ofs =
       self->descriptor->layout->
       fields[upb_fielddef_index(first_field)].case_offset;
-  uint32_t oneof_case = *((uint32_t*)((char*)Message_data(self) + case_ofs));
+  oneof_case = *((uint32_t*)((char*)Message_data(self) + case_ofs));
 
   if (oneof_case == ONEOF_CASE_NONE) {
     return Qnil;
   }
 
   // oneof_case is a field index, so find that field.
-  const upb_fielddef* f = upb_oneofdef_itof(o, oneof_case);
+  f = upb_oneofdef_itof(o, oneof_case);
   assert(f != NULL);
 
   return ID2SYM(rb_intern(upb_fielddef_name(f)));
@@ -118,18 +125,25 @@
  */
 VALUE Message_method_missing(int argc, VALUE* argv, VALUE _self) {
   MessageHeader* self;
+  VALUE method_name, method_str;
+  char* name;
+  size_t name_len;
+  bool setter;
+  const upb_oneofdef* o;
+  const upb_fielddef* f;
+
   TypedData_Get_Struct(_self, MessageHeader, &Message_type, self);
   if (argc < 1) {
     rb_raise(rb_eArgError, "Expected method name as first argument.");
   }
-  VALUE method_name = argv[0];
+  method_name = argv[0];
   if (!SYMBOL_P(method_name)) {
     rb_raise(rb_eArgError, "Expected symbol as method name.");
   }
-  VALUE method_str = rb_id2str(SYM2ID(method_name));
-  char* name = RSTRING_PTR(method_str);
-  size_t name_len = RSTRING_LEN(method_str);
-  bool setter = false;
+  method_str = rb_id2str(SYM2ID(method_name));
+  name = RSTRING_PTR(method_str);
+  name_len = RSTRING_LEN(method_str);
+  setter = false;
 
   // Setters have names that end in '='.
   if (name[name_len - 1] == '=') {
@@ -138,7 +152,7 @@
   }
 
   // Check for a oneof name first.
-  const upb_oneofdef* o = upb_msgdef_ntoo(self->descriptor->msgdef,
+  o = upb_msgdef_ntoo(self->descriptor->msgdef,
                                           name, name_len);
   if (o != NULL) {
     if (setter) {
@@ -148,7 +162,7 @@
   }
 
   // Otherwise, check for a field with that name.
-  const upb_fielddef* f = upb_msgdef_ntof(self->descriptor->msgdef,
+  f = upb_msgdef_ntof(self->descriptor->msgdef,
                                           name, name_len);
 
   if (f == NULL) {
@@ -168,6 +182,9 @@
 
 int Message_initialize_kwarg(VALUE key, VALUE val, VALUE _self) {
   MessageHeader* self;
+  VALUE method_str;
+  char* name;
+  const upb_fielddef* f;
   TypedData_Get_Struct(_self, MessageHeader, &Message_type, self);
 
   if (!SYMBOL_P(key)) {
@@ -175,27 +192,31 @@
              "Expected symbols as hash keys in initialization map.");
   }
 
-  VALUE method_str = rb_id2str(SYM2ID(key));
-  char* name = RSTRING_PTR(method_str);
-  const upb_fielddef* f = upb_msgdef_ntofz(self->descriptor->msgdef, name);
+  method_str = rb_id2str(SYM2ID(key));
+  name = RSTRING_PTR(method_str);
+  f = upb_msgdef_ntofz(self->descriptor->msgdef, name);
   if (f == NULL) {
     rb_raise(rb_eArgError,
              "Unknown field name in initialization map entry.");
   }
 
   if (is_map_field(f)) {
+    VALUE map;
+
     if (TYPE(val) != T_HASH) {
       rb_raise(rb_eArgError,
                "Expected Hash object as initializer value for map field.");
     }
-    VALUE map = layout_get(self->descriptor->layout, Message_data(self), f);
+    map = layout_get(self->descriptor->layout, Message_data(self), f);
     Map_merge_into_self(map, val);
   } else if (upb_fielddef_label(f) == UPB_LABEL_REPEATED) {
+    VALUE ary;
+
     if (TYPE(val) != T_ARRAY) {
       rb_raise(rb_eArgError,
                "Expected array as initializer value for repeated field.");
     }
-    VALUE ary = layout_get(self->descriptor->layout, Message_data(self), f);
+    ary = layout_get(self->descriptor->layout, Message_data(self), f);
     for (int i = 0; i < RARRAY_LEN(val); i++) {
       RepeatedField_push(ary, rb_ary_entry(val, i));
     }
@@ -218,13 +239,15 @@
  * Message class are provided on each concrete message class.
  */
 VALUE Message_initialize(int argc, VALUE* argv, VALUE _self) {
+  VALUE hash_args;
+
   if (argc == 0) {
     return Qnil;
   }
   if (argc != 1) {
     rb_raise(rb_eArgError, "Expected 0 or 1 arguments.");
   }
-  VALUE hash_args = argv[0];
+  hash_args = argv[0];
   if (TYPE(hash_args) != T_HASH) {
     rb_raise(rb_eArgError, "Expected hash arguments.");
   }
@@ -241,10 +264,11 @@
  */
 VALUE Message_dup(VALUE _self) {
   MessageHeader* self;
+  VALUE new_msg;
+  MessageHeader* new_msg_self;
   TypedData_Get_Struct(_self, MessageHeader, &Message_type, self);
 
-  VALUE new_msg = rb_class_new_instance(0, NULL, CLASS_OF(_self));
-  MessageHeader* new_msg_self;
+  new_msg = rb_class_new_instance(0, NULL, CLASS_OF(_self));
   TypedData_Get_Struct(new_msg, MessageHeader, &Message_type, new_msg_self);
 
   layout_dup(self->descriptor->layout,
@@ -257,10 +281,11 @@
 // Internal only; used by Google::Protobuf.deep_copy.
 VALUE Message_deep_copy(VALUE _self) {
   MessageHeader* self;
+  MessageHeader* new_msg_self;
+  VALUE new_msg;
   TypedData_Get_Struct(_self, MessageHeader, &Message_type, self);
 
-  VALUE new_msg = rb_class_new_instance(0, NULL, CLASS_OF(_self));
-  MessageHeader* new_msg_self;
+  new_msg = rb_class_new_instance(0, NULL, CLASS_OF(_self));
   TypedData_Get_Struct(new_msg, MessageHeader, &Message_type, new_msg_self);
 
   layout_deep_copy(self->descriptor->layout,
@@ -281,9 +306,8 @@
  */
 VALUE Message_eq(VALUE _self, VALUE _other) {
   MessageHeader* self;
-  TypedData_Get_Struct(_self, MessageHeader, &Message_type, self);
-
   MessageHeader* other;
+  TypedData_Get_Struct(_self, MessageHeader, &Message_type, self);
   TypedData_Get_Struct(_other, MessageHeader, &Message_type, other);
 
   if (self->descriptor != other->descriptor) {
@@ -318,9 +342,10 @@
  */
 VALUE Message_inspect(VALUE _self) {
   MessageHeader* self;
+  VALUE str;
   TypedData_Get_Struct(_self, MessageHeader, &Message_type, self);
 
-  VALUE str = rb_str_new2("<");
+  str = rb_str_new2("<");
   str = rb_str_append(str, rb_str_new2(rb_class2name(CLASS_OF(_self))));
   str = rb_str_cat2(str, ": ");
   str = rb_str_append(str, layout_inspect(
@@ -332,11 +357,12 @@
 
 VALUE Message_to_h(VALUE _self) {
   MessageHeader* self;
+  VALUE hash;
+  upb_msg_field_iter it;
   TypedData_Get_Struct(_self, MessageHeader, &Message_type, self);
 
-  VALUE hash = rb_hash_new();
+  hash = rb_hash_new();
 
-  upb_msg_field_iter it;
   for (upb_msg_field_begin(&it, self->descriptor->msgdef);
        !upb_msg_field_done(&it);
        upb_msg_field_next(&it)) {
@@ -363,10 +389,10 @@
  */
 VALUE Message_index(VALUE _self, VALUE field_name) {
   MessageHeader* self;
+  const upb_fielddef* field;
   TypedData_Get_Struct(_self, MessageHeader, &Message_type, self);
   Check_Type(field_name, T_STRING);
-  const upb_fielddef* field =
-      upb_msgdef_ntofz(self->descriptor->msgdef, RSTRING_PTR(field_name));
+  field = upb_msgdef_ntofz(self->descriptor->msgdef, RSTRING_PTR(field_name));
   if (field == NULL) {
     return Qnil;
   }
@@ -382,10 +408,10 @@
  */
 VALUE Message_index_set(VALUE _self, VALUE field_name, VALUE value) {
   MessageHeader* self;
+  const upb_fielddef* field;
   TypedData_Get_Struct(_self, MessageHeader, &Message_type, self);
   Check_Type(field_name, T_STRING);
-  const upb_fielddef* field =
-      upb_msgdef_ntofz(self->descriptor->msgdef, RSTRING_PTR(field_name));
+  field = upb_msgdef_ntofz(self->descriptor->msgdef, RSTRING_PTR(field_name));
   if (field == NULL) {
     rb_raise(rb_eArgError, "Unknown field: %s", RSTRING_PTR(field_name));
   }
@@ -405,6 +431,9 @@
 }
 
 VALUE build_class_from_descriptor(Descriptor* desc) {
+  const char *name;
+  VALUE klass;
+
   if (desc->layout == NULL) {
     desc->layout = create_layout(desc->msgdef);
   }
@@ -412,12 +441,12 @@
     desc->fill_method = new_fillmsg_decodermethod(desc, &desc->fill_method);
   }
 
-  const char* name = upb_msgdef_fullname(desc->msgdef);
+  name = upb_msgdef_fullname(desc->msgdef);
   if (name == NULL) {
     rb_raise(rb_eRuntimeError, "Descriptor does not have assigned name.");
   }
 
-  VALUE klass = rb_define_class_id(
+  klass = rb_define_class_id(
       // Docs say this parameter is ignored. User will assign return value to
       // their own toplevel constant class name.
       rb_intern("Message"),
diff --git a/ruby/ext/google/protobuf_c/protobuf.c b/ruby/ext/google/protobuf_c/protobuf.c
index d0625a1..32e3aea 100644
--- a/ruby/ext/google/protobuf_c/protobuf.c
+++ b/ruby/ext/google/protobuf_c/protobuf.c
@@ -80,10 +80,11 @@
 // This must be named "Init_protobuf_c" because the Ruby module is named
 // "protobuf_c" -- the VM looks for this symbol in our .so.
 void Init_protobuf_c() {
-  descriptor_instancevar_interned = rb_intern(kDescriptorInstanceVar);
   VALUE google = rb_define_module("Google");
   VALUE protobuf = rb_define_module_under(google, "Protobuf");
   VALUE internal = rb_define_module_under(protobuf, "Internal");
+
+  descriptor_instancevar_interned = rb_intern(kDescriptorInstanceVar);
   DescriptorPool_register(protobuf);
   Descriptor_register(protobuf);
   FieldDescriptor_register(protobuf);
diff --git a/ruby/ext/google/protobuf_c/repeated_field.c b/ruby/ext/google/protobuf_c/repeated_field.c
index ffa60c1..72687f2 100644
--- a/ruby/ext/google/protobuf_c/repeated_field.c
+++ b/ruby/ext/google/protobuf_c/repeated_field.c
@@ -47,6 +47,10 @@
   return self;
 }
 
+void* RepeatedField_memoryat(RepeatedField* self, int index, int element_size) {
+  return ((uint8_t *)self->elements) + index * element_size;
+}
+
 static int index_position(VALUE _index, RepeatedField* repeated_field) {
   int index = NUM2INT(_index);
   if (index < 0 && repeated_field->size > 0) {
@@ -113,16 +117,15 @@
   if (argc == 1){
     if (FIXNUM_P(arg)) {
       /* standard case */
+      void* memory;
       int index = index_position(argv[0], self);
       if (index < 0 || index >= self->size) {
         return Qnil;
       }
-      void* memory = (void *) (((uint8_t *)self->elements) +
-                               index * element_size);
+      memory = RepeatedField_memoryat(self, index, element_size);
       return native_slot_get(field_type, field_type_class, memory);
     }else{
       /* check if idx is Range */
-      size_t off;
       switch (rb_range_beg_len(arg, &beg, &len, self->size, 0)) {
         case Qfalse:
           break;
@@ -157,23 +160,24 @@
   upb_fieldtype_t field_type = self->field_type;
   VALUE field_type_class = self->field_type_class;
   int element_size = native_slot_size(field_type);
+  void* memory;
 
   int index = index_position(_index, self);
   if (index < 0 || index >= (INT_MAX - 1)) {
     return Qnil;
   }
   if (index >= self->size) {
-    RepeatedField_reserve(self, index + 1);
     upb_fieldtype_t field_type = self->field_type;
     int element_size = native_slot_size(field_type);
+    RepeatedField_reserve(self, index + 1);
     for (int i = self->size; i <= index; i++) {
-      void* elem = (void *)(((uint8_t *)self->elements) + i * element_size);
+      void* elem = RepeatedField_memoryat(self, i, element_size);
       native_slot_init(field_type, elem);
     }
     self->size = index + 1;
   }
 
-  void* memory = (void *) (((uint8_t *)self->elements) + index * element_size);
+  memory = RepeatedField_memoryat(self, index, element_size);
   native_slot_set(field_type, field_type_class, memory, val);
   return Qnil;
 }
@@ -181,6 +185,8 @@
 static int kInitialSize = 8;
 
 void RepeatedField_reserve(RepeatedField* self, int new_size) {
+  void* old_elems = self->elements;
+  int elem_size = native_slot_size(self->field_type);
   if (new_size <= self->capacity) {
     return;
   }
@@ -190,8 +196,6 @@
   while (self->capacity < new_size) {
     self->capacity *= 2;
   }
-  void* old_elems = self->elements;
-  int elem_size = native_slot_size(self->field_type);
   self->elements = ALLOC_N(uint8_t, elem_size * self->capacity);
   if (old_elems != NULL) {
     memcpy(self->elements, old_elems, self->size * elem_size);
@@ -209,11 +213,12 @@
   RepeatedField* self = ruby_to_RepeatedField(_self);
   upb_fieldtype_t field_type = self->field_type;
   int element_size = native_slot_size(field_type);
+  void* memory;
+
   RepeatedField_reserve(self, self->size + 1);
-  int index = self->size;
-  void* memory = (void *) (((uint8_t *)self->elements) + index * element_size);
+  memory = (void *) (((uint8_t *)self->elements) + self->size * element_size);
   native_slot_set(field_type, self->field_type_class, memory, val);
-  // native_slot_set may raise an error; bump index only after set.
+  // native_slot_set may raise an error; bump size only after set.
   self->size++;
   return _self;
 }
@@ -224,9 +229,10 @@
   RepeatedField* self = ruby_to_RepeatedField(_self);
   upb_fieldtype_t field_type = self->field_type;
   int element_size = native_slot_size(field_type);
+  void* memory;
+
   RepeatedField_reserve(self, self->size + 1);
-  int index = self->size;
-  void* memory = (void *) (((uint8_t *)self->elements) + index * element_size);
+  memory = (void *) (((uint8_t *)self->elements) + self->size * element_size);
   memcpy(memory, data, element_size);
   self->size++;
 }
@@ -235,7 +241,7 @@
   RepeatedField* self = ruby_to_RepeatedField(_self);
   upb_fieldtype_t field_type = self->field_type;
   int element_size = native_slot_size(field_type);
-  return ((uint8_t *)self->elements) + index * element_size;
+  return RepeatedField_memoryat(self, index, element_size);
 }
 
 /*
@@ -246,12 +252,16 @@
   upb_fieldtype_t field_type = self->field_type;
   VALUE field_type_class = self->field_type_class;
   int element_size = native_slot_size(field_type);
+  int index;
+  void* memory;
+  VALUE ret;
+
   if (self->size == 0) {
     return Qnil;
   }
-  int index = self->size - 1;
-  void* memory = (void *) (((uint8_t *)self->elements) + index * element_size);
-  VALUE ret = native_slot_get(field_type, field_type_class, memory);
+  index = self->size - 1;
+  memory = RepeatedField_memoryat(self, index, element_size);
+  ret = native_slot_get(field_type, field_type_class, memory);
   self->size--;
   return ret;
 }
@@ -320,10 +330,10 @@
   RepeatedField* self = ruby_to_RepeatedField(_self);
   VALUE new_rptfield = RepeatedField_new_this_type(_self);
   RepeatedField* new_rptfield_self = ruby_to_RepeatedField(new_rptfield);
-  RepeatedField_reserve(new_rptfield_self, self->size);
   upb_fieldtype_t field_type = self->field_type;
   size_t elem_size = native_slot_size(field_type);
   size_t off = 0;
+  RepeatedField_reserve(new_rptfield_self, self->size);
   for (int i = 0; i < self->size; i++, off += elem_size) {
     void* to_mem = (uint8_t *)new_rptfield_self->elements + off;
     void* from_mem = (uint8_t *)self->elements + off;
@@ -339,10 +349,10 @@
   RepeatedField* self = ruby_to_RepeatedField(_self);
   VALUE new_rptfield = RepeatedField_new_this_type(_self);
   RepeatedField* new_rptfield_self = ruby_to_RepeatedField(new_rptfield);
-  RepeatedField_reserve(new_rptfield_self, self->size);
   upb_fieldtype_t field_type = self->field_type;
   size_t elem_size = native_slot_size(field_type);
   size_t off = 0;
+  RepeatedField_reserve(new_rptfield_self, self->size);
   for (int i = 0; i < self->size; i++, off += elem_size) {
     void* to_mem = (uint8_t *)new_rptfield_self->elements + off;
     void* from_mem = (uint8_t *)self->elements + off;
@@ -389,34 +399,39 @@
  * indicated that every element has equal value.
  */
 VALUE RepeatedField_eq(VALUE _self, VALUE _other) {
+  RepeatedField* self;
+  RepeatedField* other;
+
   if (_self == _other) {
     return Qtrue;
   }
-  RepeatedField* self = ruby_to_RepeatedField(_self);
 
   if (TYPE(_other) == T_ARRAY) {
     VALUE self_ary = RepeatedField_to_ary(_self);
     return rb_equal(self_ary, _other);
   }
 
-  RepeatedField* other = ruby_to_RepeatedField(_other);
+  self = ruby_to_RepeatedField(_self);
+  other = ruby_to_RepeatedField(_other);
   if (self->field_type != other->field_type ||
       self->field_type_class != other->field_type_class ||
       self->size != other->size) {
     return Qfalse;
   }
 
-  upb_fieldtype_t field_type = self->field_type;
-  size_t elem_size = native_slot_size(field_type);
-  size_t off = 0;
-  for (int i = 0; i < self->size; i++, off += elem_size) {
-    void* self_mem = ((uint8_t *)self->elements) + off;
-    void* other_mem = ((uint8_t *)other->elements) + off;
-    if (!native_slot_eq(field_type, self_mem, other_mem)) {
-      return Qfalse;
+  {
+    upb_fieldtype_t field_type = self->field_type;
+    size_t elem_size = native_slot_size(field_type);
+    size_t off = 0;
+    for (int i = 0; i < self->size; i++, off += elem_size) {
+      void* self_mem = ((uint8_t *)self->elements) + off;
+      void* other_mem = ((uint8_t *)other->elements) + off;
+      if (!native_slot_eq(field_type, self_mem, other_mem)) {
+        return Qfalse;
+      }
     }
+    return Qtrue;
   }
-  return Qtrue;
 }
 
 /*
@@ -488,7 +503,6 @@
  * concats the passed in array to self.  Returns a Ruby array.
  */
 VALUE RepeatedField_concat(VALUE _self, VALUE list) {
-  RepeatedField* self = ruby_to_RepeatedField(_self);
   Check_Type(list, T_ARRAY);
   for (int i = 0; i < RARRAY_LEN(list); i++) {
     RepeatedField_push(_self, rb_ary_entry(list, i));
@@ -564,9 +578,9 @@
 
 void RepeatedField_mark(void* _self) {
   RepeatedField* self = (RepeatedField*)_self;
-  rb_gc_mark(self->field_type_class);
   upb_fieldtype_t field_type = self->field_type;
   int element_size = native_slot_size(field_type);
+  rb_gc_mark(self->field_type_class);
   for (int i = 0; i < self->size; i++) {
     void* memory = (((uint8_t *)self->elements) + i * element_size);
     native_slot_mark(self->field_type, memory);
@@ -592,12 +606,12 @@
  */
 VALUE RepeatedField_alloc(VALUE klass) {
   RepeatedField* self = ALLOC(RepeatedField);
+  VALUE ret = TypedData_Wrap_Struct(klass, &RepeatedField_type, self);
   self->elements = NULL;
   self->size = 0;
   self->capacity = 0;
   self->field_type = -1;
   self->field_type_class = Qnil;
-  VALUE ret = TypedData_Wrap_Struct(klass, &RepeatedField_type, self);
   return ret;
 }
 
diff --git a/ruby/ext/google/protobuf_c/storage.c b/ruby/ext/google/protobuf_c/storage.c
index c4cdc9c..b1f65f4 100644
--- a/ruby/ext/google/protobuf_c/storage.c
+++ b/ruby/ext/google/protobuf_c/storage.c
@@ -166,11 +166,11 @@
       break;
     }
     case UPB_TYPE_ENUM: {
+      int32_t int_val = 0;
       if (!is_ruby_num(value) && TYPE(value) != T_SYMBOL) {
         rb_raise(rb_eTypeError,
                  "Expected number or symbol type for enum field.");
       }
-      int32_t int_val = 0;
       if (TYPE(value) == T_SYMBOL) {
         // Ensure that the given symbol exists in the enum module.
         VALUE lookup = rb_funcall(type_class, rb_intern("resolve"), 1, value);
@@ -346,24 +346,33 @@
 // Map field utilities.
 // -----------------------------------------------------------------------------
 
-bool is_map_field(const upb_fielddef* field) {
+const upb_msgdef* tryget_map_entry_msgdef(const upb_fielddef* field) {
+  const upb_msgdef* subdef;
   if (upb_fielddef_label(field) != UPB_LABEL_REPEATED ||
       upb_fielddef_type(field) != UPB_TYPE_MESSAGE) {
-    return false;
+    return NULL;
   }
-  const upb_msgdef* subdef = upb_fielddef_msgsubdef(field);
-  return upb_msgdef_mapentry(subdef);
+  subdef = upb_fielddef_msgsubdef(field);
+  return upb_msgdef_mapentry(subdef) ? subdef : NULL;
+}
+
+const upb_msgdef *map_entry_msgdef(const upb_fielddef* field) {
+  const upb_msgdef* subdef = tryget_map_entry_msgdef(field);
+  assert(subdef);
+  return subdef;
+}
+
+bool is_map_field(const upb_fielddef *field) {
+  return tryget_map_entry_msgdef(field) != NULL;
 }
 
 const upb_fielddef* map_field_key(const upb_fielddef* field) {
-  assert(is_map_field(field));
-  const upb_msgdef* subdef = upb_fielddef_msgsubdef(field);
+  const upb_msgdef* subdef = map_entry_msgdef(field);
   return map_entry_key(subdef);
 }
 
 const upb_fielddef* map_field_value(const upb_fielddef* field) {
-  assert(is_map_field(field));
-  const upb_msgdef* subdef = upb_fielddef_msgsubdef(field);
+  const upb_msgdef* subdef = map_entry_msgdef(field);
   return map_entry_value(subdef);
 }
 
@@ -391,14 +400,17 @@
 MessageLayout* create_layout(const upb_msgdef* msgdef) {
   MessageLayout* layout = ALLOC(MessageLayout);
   int nfields = upb_msgdef_numfields(msgdef);
+  upb_msg_field_iter it;
+  upb_msg_oneof_iter oit;
+  size_t off = 0;
+
   layout->fields = ALLOC_N(MessageField, nfields);
 
-  upb_msg_field_iter it;
-  size_t off = 0;
   for (upb_msg_field_begin(&it, msgdef);
        !upb_msg_field_done(&it);
        upb_msg_field_next(&it)) {
     const upb_fielddef* field = upb_msg_iter_field(&it);
+    size_t field_size;
 
     if (upb_fielddef_containingoneof(field)) {
       // Oneofs are handled separately below.
@@ -406,7 +418,7 @@
     }
 
     // Allocate |field_size| bytes for this field in the layout.
-    size_t field_size = 0;
+    field_size = 0;
     if (upb_fielddef_label(field) == UPB_LABEL_REPEATED) {
       field_size = sizeof(VALUE);
     } else {
@@ -433,11 +445,11 @@
   // members (8 or 16 bits respectively), so conceivably we could assign
   // consecutive case numbers and then pick a smaller oneof case slot size, but
   // the complexity to implement this indirection is probably not worthwhile.
-  upb_msg_oneof_iter oit;
   for (upb_msg_oneof_begin(&oit, msgdef);
        !upb_msg_oneof_done(&oit);
        upb_msg_oneof_next(&oit)) {
     const upb_oneofdef* oneof = upb_msg_iter_oneof(&oit);
+    upb_oneof_iter fit;
 
     // Always allocate NATIVE_SLOT_MAX_SIZE bytes, but share the slot between
     // all fields.
@@ -445,7 +457,6 @@
     // Align the offset.
     off = align_up_to(off, field_size);
     // Assign all fields in the oneof this same offset.
-    upb_oneof_iter fit;
     for (upb_oneof_begin(&fit, oneof);
          !upb_oneof_done(&fit);
          upb_oneof_next(&fit)) {
@@ -460,12 +471,12 @@
        !upb_msg_oneof_done(&oit);
        upb_msg_oneof_next(&oit)) {
     const upb_oneofdef* oneof = upb_msg_iter_oneof(&oit);
+    upb_oneof_iter fit;
 
     size_t field_size = sizeof(uint32_t);
     // Align the offset.
     off = (off + field_size - 1) & ~(field_size - 1);
     // Assign all fields in the oneof this same offset.
-    upb_oneof_iter fit;
     for (upb_oneof_begin(&fit, oneof);
          !upb_oneof_done(&fit);
          upb_oneof_next(&fit)) {
@@ -541,6 +552,7 @@
 }
 
 static void check_repeated_field_type(VALUE val, const upb_fielddef* field) {
+  RepeatedField* self;
   assert(upb_fielddef_label(field) == UPB_LABEL_REPEATED);
 
   if (!RB_TYPE_P(val, T_DATA) || !RTYPEDDATA_P(val) ||
@@ -548,7 +560,7 @@
     rb_raise(rb_eTypeError, "Expected repeated field array");
   }
 
-  RepeatedField* self = ruby_to_RepeatedField(val);
+  self = ruby_to_RepeatedField(val);
   if (self->field_type != upb_fielddef_type(field)) {
     rb_raise(rb_eTypeError, "Repeated field array has wrong element type");
   }
@@ -564,16 +576,16 @@
 }
 
 static void check_map_field_type(VALUE val, const upb_fielddef* field) {
-  assert(is_map_field(field));
   const upb_fielddef* key_field = map_field_key(field);
   const upb_fielddef* value_field = map_field_value(field);
+  Map* self;
 
   if (!RB_TYPE_P(val, T_DATA) || !RTYPEDDATA_P(val) ||
       RTYPEDDATA_TYPE(val) != &Map_type) {
     rb_raise(rb_eTypeError, "Expected Map instance");
   }
 
-  Map* self = ruby_to_Map(val);
+  self = ruby_to_Map(val);
   if (self->key_type != upb_fielddef_type(key_field)) {
     rb_raise(rb_eTypeError, "Map key type does not match field's key type");
   }