diff --git a/Makefile b/Makefile
index 33cd4f9fd6..73e5b6573b 100644
--- a/Makefile
+++ b/Makefile
@@ -2,18 +2,19 @@
 # Function to expand a wildcard pattern recursively.
 rwildcard=$(strip $(foreach d,$(wildcard $1*),$(call rwildcard,$d/,$2)$(filter $(subst *,%,$2),$d)))
 
-.PHONY: all clean test benchmarks benchmark
+.PHONY: all clean test benchmarks benchmark descriptorgen
 CC=gcc
 CXX=g++
 CFLAGS=-std=c99
 INCLUDE=-Idescriptor -Isrc -Itests -I.
-CPPFLAGS=-O3 -Wall -Wextra -g $(INCLUDE) $(strip $(shell test -f perf-cppflags && cat perf-cppflags))
+CPPFLAGS=-Wall -Wextra -g $(INCLUDE) $(strip $(shell test -f perf-cppflags && cat perf-cppflags))
 
 LIBUPB=src/libupb.a
 ALL=deps $(OBJ) $(LIBUPB) tests/test_table tests/tests tools/upbc
 all: $(ALL)
 clean:
 	rm -f $(call rwildcard,,*.o) $(ALL) benchmark/google_messages.proto.pb benchmark/google_messages.pb.* benchmarks/b.* benchmarks/*.pb*
+	rm -f descriptor/descriptor.proto.pb
 
 # The core library (src/libupb.a)
 OBJ=src/upb_parse.o src/upb_table.o src/upb_msg.o src/upb_enum.o src/upb_context.o \
@@ -23,6 +24,14 @@ HEADERS=$(call rwildcard,,*.h)
 $(LIBUPB): $(OBJ)
 	ar rcs $(LIBUPB) $(OBJ)
 
+# Regenerating the auto-generated files in descriptor/.
+descriptor/descriptor.proto.pb: descriptor/descriptor.proto
+	# TODO: replace with upbc
+	protoc descriptor/descriptor.proto -odescriptor/descriptor.proto.pb
+
+descriptorgen: descriptor/descriptor.proto.pb tools/upbc
+	./tools/upbc -i upb_file_descriptor_set -o descriptor/descriptor descriptor/descriptor.proto.pb
+
 # Tests
 test: tests/tests
 	./tests/tests
diff --git a/descriptor/descriptor.h b/descriptor/descriptor.h
index 39d31175b1..70960239fe 100644
--- a/descriptor/descriptor.h
+++ b/descriptor/descriptor.h
@@ -131,6 +131,8 @@ typedef struct google_protobuf_MethodOptions
 /* The message definitions themselves. */
 
 struct google_protobuf_UninterpretedOption_NamePart {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -144,6 +146,8 @@ struct google_protobuf_UninterpretedOption_NamePart {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_UninterpretedOption_NamePart)
 
 struct google_protobuf_DescriptorProto {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -167,6 +171,8 @@ struct google_protobuf_DescriptorProto {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_DescriptorProto)
 
 struct google_protobuf_EnumDescriptorProto {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -182,6 +188,8 @@ struct google_protobuf_EnumDescriptorProto {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_EnumDescriptorProto)
 
 struct google_protobuf_UninterpretedOption {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -203,6 +211,8 @@ struct google_protobuf_UninterpretedOption {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_UninterpretedOption)
 
 struct google_protobuf_FileDescriptorProto {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -228,6 +238,8 @@ struct google_protobuf_FileDescriptorProto {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_FileDescriptorProto)
 
 struct google_protobuf_MethodDescriptorProto {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -245,6 +257,8 @@ struct google_protobuf_MethodDescriptorProto {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_MethodDescriptorProto)
 
 struct google_protobuf_EnumValueOptions {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -256,6 +270,8 @@ struct google_protobuf_EnumValueOptions {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_EnumValueOptions)
 
 struct google_protobuf_EnumValueDescriptorProto {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -271,6 +287,8 @@ struct google_protobuf_EnumValueDescriptorProto {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_EnumValueDescriptorProto)
 
 struct google_protobuf_ServiceDescriptorProto {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -286,6 +304,8 @@ struct google_protobuf_ServiceDescriptorProto {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_ServiceDescriptorProto)
 
 struct google_protobuf_FileDescriptorSet {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -297,6 +317,8 @@ struct google_protobuf_FileDescriptorSet {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_FileDescriptorSet)
 
 struct google_protobuf_DescriptorProto_ExtensionRange {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -310,6 +332,8 @@ struct google_protobuf_DescriptorProto_ExtensionRange {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_DescriptorProto_ExtensionRange)
 
 struct google_protobuf_FieldOptions {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -329,6 +353,8 @@ struct google_protobuf_FieldOptions {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_FieldOptions)
 
 struct google_protobuf_FileOptions {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -348,6 +374,8 @@ struct google_protobuf_FileOptions {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_FileOptions)
 
 struct google_protobuf_MessageOptions {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -361,6 +389,8 @@ struct google_protobuf_MessageOptions {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_MessageOptions)
 
 struct google_protobuf_EnumOptions {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -372,6 +402,8 @@ struct google_protobuf_EnumOptions {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_EnumOptions)
 
 struct google_protobuf_FieldDescriptorProto {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -397,6 +429,8 @@ struct google_protobuf_FieldDescriptorProto {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_FieldDescriptorProto)
 
 struct google_protobuf_ServiceOptions {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
@@ -408,6 +442,8 @@ struct google_protobuf_ServiceOptions {
 UPB_DEFINE_MSG_ARRAY(google_protobuf_ServiceOptions)
 
 struct google_protobuf_MethodOptions {
+  struct upb_msgdef *def;
+  void *gptr;
   union {
     uint8_t bytes[1];
     struct {
diff --git a/perf-tests.sh b/perf-tests.sh
index 28873f2267..1d8f4a8d2e 100755
--- a/perf-tests.sh
+++ b/perf-tests.sh
@@ -11,23 +11,23 @@ fi
 rm -f perf-tests.out
 
 make clean
-echo "-DNDEBUG -msse3" > perf-cppflags
+echo "-O3 -DNDEBUG -msse3" > perf-cppflags
 make $MAKETARGET
 make benchmark | sed -e 's/^/plain./g' | tee -a perf-tests.out
 
 make clean
-echo "-DNDEBUG -fomit-frame-pointer -msse3" > perf-cppflags
+echo "-O3 -DNDEBUG -fomit-frame-pointer -msse3" > perf-cppflags
 make $MAKETARGET
 make benchmark | sed -e 's/^/omitfp./g' | tee -a perf-tests.out
 
 if [ x`uname -m` == xx86_64 ]; then
   make clean
-  echo "-DNDEBUG -msse3 -m32" > perf-cppflags
+  echo "-O3 -DNDEBUG -msse3 -m32" > perf-cppflags
   make upb_benchmarks
   make benchmark | sed -e 's/^/plain32./g' | tee -a perf-tests.out
 
   make clean
-  echo "-DNDEBUG -fomit-frame-pointer -msse3 -m32" > perf-cppflags
+  echo "-O3 -DNDEBUG -fomit-frame-pointer -msse3 -m32" > perf-cppflags
   make upb_benchmarks
   make benchmark | sed -e 's/^/omitfp32./g' | tee -a perf-tests.out
 fi
diff --git a/src/upb.h b/src/upb.h
index 83917af2ac..27bf5fc7be 100644
--- a/src/upb.h
+++ b/src/upb.h
@@ -35,8 +35,6 @@ extern "C" {
 
 #define UPB_INDEX(base, i, m) (void*)((char*)(base) + ((i)*(m)))
 
-INLINE uint32_t max(uint32_t a, uint32_t b) { return a > b ? a : b; }
-
 /* Fundamental types and type constants. **************************************/
 
 /* A list of types as they are encoded on-the-wire. */
@@ -104,7 +102,7 @@ union upb_value {
   bool     _bool;
   struct upb_string *str;
   struct upb_array *arr;
-  void     *msg;
+  struct upb_msg *msg;
 };
 
 /* A pointer to a .proto value.  The owner must have an out-of-band way of
@@ -119,7 +117,7 @@ union upb_value_ptr {
   bool     *_bool;
   struct upb_string **str;
   struct upb_array **arr;
-  void     **msg;
+  struct upb_msg **msg;
   void     *_void;
 };
 
diff --git a/src/upb_array.h b/src/upb_array.h
index d48aa17627..65d44bb4d8 100644
--- a/src/upb_array.h
+++ b/src/upb_array.h
@@ -38,22 +38,32 @@ typedef uint32_t upb_arraylen_t;
  * the data in the array depends on the type. */
 struct upb_array {
   union upb_value_ptr elements;
-  void *mem;
   upb_arraylen_t len;     /* Number of elements in "elements". */
-  upb_arraylen_t size;    /* Memory allocated in "mem" (measured in elements) */
+  upb_arraylen_t size;    /* Memory we own (0 if by reference). */
+  void *gptr;
 };
 
 INLINE void upb_array_init(struct upb_array *arr)
 {
   arr->elements._void = NULL;
-  arr->mem = NULL;
   arr->len = 0;
   arr->size = 0;
 }
 
-INLINE void upb_array_free(struct upb_array *arr)
+INLINE void upb_array_uninit(struct upb_array *arr)
 {
-  free(arr->mem);
+  if(arr->size) free(arr->elements._void);
+}
+
+INLINE struct upb_array *upb_array_new() {
+  struct upb_array *arr = malloc(sizeof(*arr));
+  upb_array_init(arr);
+  return arr;
+}
+
+INLINE void upb_array_free(struct upb_array *arr) {
+  upb_array_uninit(arr);
+  free(arr);
 }
 
 /* Returns a pointer to an array element.  Does not perform a bounds check! */
@@ -92,18 +102,18 @@ INLINE bool upb_array_resize(struct upb_array *arr, upb_arraylen_t newlen,
 {
   size_t type_size = upb_type_info[type].size;
   bool dropped = false;
-  bool ref = arr->elements._void != arr->mem;  /* Ref'ing external memory. */
+  bool ref = arr->size == 0;   /* Ref'ing external memory. */
+  void *data = arr->elements._void;
   if(arr->size < newlen) {
     /* Need to resize. */
-    arr->size = max(4, upb_round_up_to_pow2(newlen));
-    arr->mem = realloc(arr->mem, arr->size * type_size);
+    arr->size = UPB_MAX(4, upb_round_up_to_pow2(newlen));
+    arr->elements._void = realloc(ref ? NULL : data, arr->size * type_size);
   }
   if(ref) {
     /* Need to take referenced data and copy it to memory we own. */
-    memcpy(arr->mem, arr->elements._void, UPB_MIN(arr->len, newlen) * type_size);
+    memcpy(arr->elements._void, data, UPB_MIN(arr->len, newlen) * type_size);
     dropped = true;
   }
-  arr->elements._void = arr->mem;
   arr->len = newlen;
   return dropped;
 }
@@ -111,8 +121,9 @@ INLINE bool upb_array_resize(struct upb_array *arr, upb_arraylen_t newlen,
 /* These are all overlays on upb_array, pointers between them can be cast. */
 #define UPB_DEFINE_ARRAY_TYPE(name, type) \
   struct name ## _array { \
+    struct upb_fielddef *f; \
+    void *gptr; \
     type *elements; \
-    type *mem; \
     upb_arraylen_t len; \
     upb_arraylen_t size; \
   };
@@ -132,7 +143,6 @@ UPB_DEFINE_ARRAY_TYPE(upb_msg,    void*)
 #define UPB_DEFINE_MSG_ARRAY(msg_type) \
   UPB_MSG_ARRAY(msg_type) { \
     msg_type **elements; \
-    msg_type **mem; \
     upb_arraylen_t len; \
     upb_arraylen_t size; \
   };
diff --git a/src/upb_context.c b/src/upb_context.c
index 5e1833ea3f..252cf17b27 100644
--- a/src/upb_context.c
+++ b/src/upb_context.c
@@ -60,7 +60,7 @@ void upb_context_free(struct upb_context *c)
 {
   free_symtab(&c->symtab);
   for(size_t i = 0; i < c->fds_len; i++)
-    upb_msg_free(c->fds[i], c->fds_msg);
+    upb_msg_free((struct upb_msg*)c->fds[i]);
   free_symtab(&c->psymtab);
   free(c->fds);
 }
@@ -280,7 +280,7 @@ bool upb_context_addfds(struct upb_context *c,
 
 bool upb_context_parsefds(struct upb_context *c, struct upb_string *fds_str) {
   google_protobuf_FileDescriptorSet *fds =
-      upb_msg_parsenew(c->fds_msg, fds_str);
+      (google_protobuf_FileDescriptorSet*)upb_msg_parsenew(c->fds_msg, fds_str);
   if(!fds) return false;
   if(!upb_context_addfds(c, fds)) return false;
 
diff --git a/src/upb_msg.c b/src/upb_msg.c
index 16c24c099c..dd627ebe94 100644
--- a/src/upb_msg.c
+++ b/src/upb_msg.c
@@ -82,7 +82,7 @@ bool upb_msgdef_init(struct upb_msgdef *m, google_protobuf_DescriptorProto *d,
     f->type = fd->type;
     f->label = fd->label;
     m->size = f->byte_offset + type_info->size;
-    max_align = max(max_align, type_info->align);
+    max_align = UPB_MAX(max_align, type_info->align);
     if(fd->label == GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_LABEL_REQUIRED)
       m->num_required_fields++;
 
@@ -123,59 +123,49 @@ void upb_msgdef_ref(struct upb_msgdef *m, struct upb_msg_fielddef *f,
 
 /* Simple, one-shot parsing ***************************************************/
 
-void *upb_msg_new(struct upb_msgdef *md)
+static void *upb_msg_new(struct upb_msgdef *md)
 {
-  void *msg = malloc(md->size);
-  memset(msg, 0, md->size);
+  size_t size = md->size + (sizeof(void*) * 2);
+  struct upb_msg *msg = malloc(size);
+  memset(msg, 0, size);
+  msg->def = md;
   return msg;
 }
 
 /* Allocation callbacks. */
-static struct upb_array *getarray_cb(void *msg, struct upb_msgdef *md,
-                                     struct upb_array *existingval,
-                                     struct upb_msg_fielddef *f,
-                                     upb_arraylen_t len)
+struct upb_array *getarray_cb(
+    void *from_gptr, struct upb_array *existingval, struct upb_msg_fielddef *f)
 {
-  (void)msg;
-  (void)md;
+  (void)from_gptr;
   (void)existingval;  /* Don't care -- always zero. */
-  (void)len;
-  struct upb_array *arr = existingval;
-  if(!arr) {
-    arr = malloc(sizeof(*arr));
-    upb_array_init(arr);
-  }
-  upb_array_resize(arr, len, f->type);
-  return arr;
+  (void)f;
+  return upb_array_new();
 }
 
-static struct upb_string *getstring_cb(void *msg, struct upb_msgdef *md,
-                                       struct upb_string *existingval,
-                                       struct upb_msg_fielddef *f, size_t len)
+static struct upb_string *getstring_cb(
+    void *from_gptr, struct upb_string *existingval, struct upb_msg_fielddef *f,
+    bool byref)
 {
-  (void)msg;
-  (void)md;
+  (void)from_gptr;
   (void)existingval;  /* Don't care -- always zero. */
   (void)f;
-  struct upb_string *str = malloc(sizeof(*str));
-  str->ptr = malloc(len);
-  return str;
+  (void)byref;
+  return upb_strnew();
 }
 
-static void *getmsg_cb(void *msg, struct upb_msgdef *md,
-                       void *existingval, struct upb_msg_fielddef *f)
+static struct upb_msg *getmsg_cb(
+    void *from_gptr, struct upb_msg *existingval, struct upb_msg_fielddef *f)
 {
-  (void)msg;
-  (void)md;
+  (void)from_gptr;
   (void)existingval;  /* Don't care -- always zero. */
   return upb_msg_new(f->ref.msg);
 }
 
-void *upb_msg_parsenew(struct upb_msgdef *md, struct upb_string *s)
+struct upb_msg *upb_msg_parsenew(struct upb_msgdef *md, struct upb_string *s)
 {
   struct upb_msg_parser mp;
-  void *msg = upb_msg_new(md);
-  upb_msg_parser_reset(&mp, msg, md, false);
+  struct upb_msg *msg = upb_msg_new(md);
+  upb_msg_parser_reset(&mp, msg, false);
   mp.getarray_cb = getarray_cb;
   mp.getstring_cb = getstring_cb;
   mp.getmsg_cb = getmsg_cb;
@@ -184,7 +174,7 @@ void *upb_msg_parsenew(struct upb_msgdef *md, struct upb_string *s)
   if(status == UPB_STATUS_OK && read == s->byte_len) {
     return msg;
   } else {
-    upb_msg_free(msg, md);
+    upb_msg_free(msg);
     return NULL;
   }
 }
@@ -197,28 +187,28 @@ static void free_value(union upb_value_ptr p, struct upb_msg_fielddef *f)
     free((*p.str)->ptr);
     free(*p.str);
   } else if(upb_issubmsg(f)) {
-    upb_msg_free(*p.msg, f->ref.msg);
+    upb_msg_free(*p.msg);
   }
 }
 
-void upb_msg_free(void *data, struct upb_msgdef *m)
+void upb_msg_free(struct upb_msg *msg)
 {
-  if(!data) return;  /* A very free-like thing to do. */
+  if(!msg) return;  /* A very free-like thing to do. */
+  struct upb_msgdef *m = msg->def;
   for(unsigned int i = 0; i < m->num_fields; i++) {
     struct upb_msg_fielddef *f = &m->fields[i];
-    if(!upb_msg_isset(data, f)) continue;
-    union upb_value_ptr p = upb_msg_getptr(data, f);
+    if(!upb_msg_isset(msg, f)) continue;
+    union upb_value_ptr p = upb_msg_getptr(msg, f);
     if(upb_isarray(f)) {
       assert(*p.arr);
       for(upb_arraylen_t j = 0; j < (*p.arr)->len; j++)
         free_value(upb_array_getelementptr(*p.arr, j, f->type), f);
-      free((*p.arr)->elements._void);
-      free(*p.arr);
+      upb_array_free(*p.arr);
     } else {
       free_value(p, f);
     }
   }
-  free(data);
+  free(msg);
 }
 
 /* Parsing.  ******************************************************************/
@@ -226,14 +216,18 @@ void upb_msg_free(void *data, struct upb_msgdef *m)
 /* Helper function that returns a pointer to where the next value for field "f"
  * should be stored, taking into account whether f is an array that may need to
  * be allocated or resized. */
-static union upb_value_ptr get_value_ptr(void *data, struct upb_msgdef *m,
+static union upb_value_ptr get_value_ptr(struct upb_msg *msg,
                                          struct upb_msg_fielddef *f,
-                                         upb_msg_getarray_cb_t getarray_cb)
+                                         void **gptr,
+                                         upb_msg_getandref_array_cb_t getarray_cb)
 {
-  union upb_value_ptr p = upb_msg_getptr(data, f);
+  union upb_value_ptr p = upb_msg_getptr(msg, f);
   if(upb_isarray(f)) {
-    size_t len = upb_msg_isset(data, f) ? (*p.arr)->len : 0;
-    *p.arr = getarray_cb(data, m, *p.arr, f, len + 1);
+    bool isset = upb_msg_isset(msg, f);
+    size_t len = isset ? (*p.arr)->len : 0;
+    if(!isset) *p.arr = getarray_cb(*gptr, *p.arr, f);
+    upb_array_resize(*p.arr, len+1, f->type);
+    *gptr = (*p.arr)->gptr;
     p = upb_array_getelementptr(*p.arr, len, f->type);
   }
   return p;
@@ -245,7 +239,8 @@ static upb_field_type_t tag_cb(void *udata, struct upb_tag *tag,
                                void **user_field_desc)
 {
   struct upb_msg_parser *mp = udata;
-  struct upb_msg_fielddef *f = upb_msg_fieldbynum(mp->top->m, tag->field_number);
+  struct upb_msg_fielddef *f =
+      upb_msg_fieldbynum(mp->top->msg->def, tag->field_number);
   if(!f || !upb_check_type(tag->wire_type, f->type))
     return 0;  /* Skip unknown or fields of the wrong type. */
   *user_field_desc = f;
@@ -257,8 +252,9 @@ static upb_status_t value_cb(void *udata, uint8_t *buf, uint8_t *end,
 {
   struct upb_msg_parser *mp = udata;
   struct upb_msg_fielddef *f = user_field_desc;
-  void *msg = mp->top->msg;
-  union upb_value_ptr p = get_value_ptr(msg, mp->top->m, f, mp->getarray_cb);
+  struct upb_msg *msg = mp->top->msg;
+  void *gptr = upb_msg_gptr(msg);
+  union upb_value_ptr p = get_value_ptr(msg, f, &gptr, mp->getarray_cb);
   upb_msg_set(msg, f);
   UPB_CHECK(upb_parse_value(buf, end, f->type, p, outbuf));
   return UPB_STATUS_OK;
@@ -270,16 +266,19 @@ static void str_cb(void *udata, uint8_t *str,
 {
   struct upb_msg_parser *mp = udata;
   struct upb_msg_fielddef *f = udesc;
-  void *msg = mp->top->msg;
-  union upb_value_ptr p = get_value_ptr(msg, mp->top->m, f, mp->getarray_cb);
+  struct upb_msg *msg = mp->top->msg;
+  void *gptr = upb_msg_gptr(msg);
+  union upb_value_ptr p = get_value_ptr(msg, f, &gptr, mp->getarray_cb);
   upb_msg_set(msg, f);
   if(avail_len != total_len) abort();  /* TODO: support streaming. */
-  if(avail_len == total_len && mp->byref) {
-    *p.str = mp->getstring_cb(msg, mp->top->m, *p.str, f, 0);
+  bool byref = avail_len == total_len && mp->byref;
+  *p.str = mp->getstring_cb(gptr, *p.str, f, byref);
+  if(byref) {
+    upb_strdrop(*p.str);
     (*p.str)->ptr = (char*)str;
     (*p.str)->byte_len = avail_len;
   } else {
-    *p.str = mp->getstring_cb(msg, mp->top->m, *p.str, f, total_len);
+    upb_stralloc(*p.str, total_len);
     memcpy((*p.str)->ptr, str, avail_len);
     (*p.str)->byte_len = avail_len;
   }
@@ -289,13 +288,12 @@ static void submsg_start_cb(void *udata, void *user_field_desc)
 {
   struct upb_msg_parser *mp = udata;
   struct upb_msg_fielddef *f = user_field_desc;
-  struct upb_msgdef *oldmsgdef = mp->top->m;
-  void *oldmsg = mp->top->msg;
-  union upb_value_ptr p = get_value_ptr(oldmsg, oldmsgdef, f, mp->getarray_cb);
+  struct upb_msg *oldmsg = mp->top->msg;
+  void *gptr = upb_msg_gptr(oldmsg);
+  union upb_value_ptr p = get_value_ptr(oldmsg, f, &gptr, mp->getarray_cb);
   upb_msg_set(oldmsg, f);
-  *p.msg = mp->getmsg_cb(oldmsg, oldmsgdef, *p.msg, f);
+  *p.msg = mp->getmsg_cb(gptr, *p.msg, f);
   mp->top++;
-  mp->top->m = f->ref.msg;
   mp->top->msg = *p.msg;
 }
 
@@ -307,13 +305,11 @@ static void submsg_end_cb(void *udata)
 
 /* Externally-visible functions for the msg parser. */
 
-void upb_msg_parser_reset(struct upb_msg_parser *s, void *msg,
-                          struct upb_msgdef *m, bool byref)
+void upb_msg_parser_reset(struct upb_msg_parser *s, struct upb_msg *msg, bool byref)
 {
   upb_stream_parser_reset(&s->s, s);
   s->byref = byref;
   s->top = s->stack;
-  s->top->m = m;
   s->top->msg = msg;
   s->s.tag_cb = tag_cb;
   s->s.value_cb = value_cb;
@@ -551,8 +547,7 @@ bool upb_array_eql(struct upb_array *arr1, struct upb_array *arr2,
   if(upb_issubmsg(f)) {
     if(!recursive) return true;
     for(uint32_t i = 0; i < arr1->len; i++)
-      if(!upb_msg_eql(arr1->elements.msg[i], arr2->elements.msg[i],
-         f->ref.msg, recursive))
+      if(!upb_msg_eql(arr1->elements.msg[i], arr2->elements.msg[i], recursive))
         return false;
   } else if(upb_isstring(f)) {
     for(uint32_t i = 0; i < arr1->len; i++)
@@ -566,11 +561,13 @@ bool upb_array_eql(struct upb_array *arr1, struct upb_array *arr2,
   return true;
 }
 
-bool upb_msg_eql(void *data1, void *data2, struct upb_msgdef *m, bool recursive)
+bool upb_msg_eql(struct upb_msg *msg1, struct upb_msg *msg2, bool recursive)
 {
   /* Must have the same fields set.  TODO: is this wrong?  Should we also
    * consider absent defaults equal to explicitly set defaults? */
-  if(memcmp(data1, data2, m->set_flags_bytes) != 0)
+  if(msg1->def != msg2->def) return false;
+  struct upb_msgdef *m = msg1->def;
+  if(memcmp(msg1->data, msg2->data, msg1->def->set_flags_bytes) != 0)
     return false;
 
   /* Possible optimization: create a mask of the bytes in the messages that
@@ -579,13 +576,16 @@ bool upb_msg_eql(void *data1, void *data2, struct upb_msgdef *m, bool recursive)
 
   for(uint32_t i = 0; i < m->num_fields; i++) {
     struct upb_msg_fielddef *f = &m->fields[i];
-    if(!upb_msg_isset(data1, f)) continue;
-    union upb_value_ptr p1 = upb_msg_getptr(data1, f);
-    union upb_value_ptr p2 = upb_msg_getptr(data2, f);
+    bool msg1set = upb_msg_isset(msg1, f);
+    bool msg2set = upb_msg_isset(msg2, f);
+    if(msg1set != msg2set) return false;
+    if(!msg1set) continue;
+    union upb_value_ptr p1 = upb_msg_getptr(msg1, f);
+    union upb_value_ptr p2 = upb_msg_getptr(msg2, f);
     if(upb_isarray(f)) {
       if(!upb_array_eql(*p1.arr, *p2.arr, f, recursive)) return false;
     } else if(upb_issubmsg(f)) {
-      if(recursive && !upb_msg_eql(p1.msg, p2.msg, f->ref.msg, recursive))
+      if(recursive && !upb_msg_eql(*p1.msg, *p2.msg, recursive))
         return false;
     } else if(!upb_value_eql(p1, p2, f->type)) {
       return false;
@@ -600,9 +600,10 @@ static void printval(struct upb_text_printer *printer, union upb_value_ptr p,
                      google_protobuf_FieldDescriptorProto *fd,
                      FILE *stream);
 
-static void printmsg(struct upb_text_printer *printer, void *msg,
-                     struct upb_msgdef *m, FILE *stream)
+static void printmsg(struct upb_text_printer *printer, struct upb_msg *msg,
+                     FILE *stream)
 {
+  struct upb_msgdef *m = msg->def;
   for(uint32_t i = 0; i < m->num_fields; i++) {
     struct upb_msg_fielddef *f = &m->fields[i];
     google_protobuf_FieldDescriptorProto *fd = upb_msg_field_descriptor(f, m);
@@ -626,18 +627,17 @@ static void printval(struct upb_text_printer *printer, union upb_value_ptr p,
                      FILE *stream)
 {
   if(upb_issubmsg(f)) {
-    upb_text_push(printer, *fd->name, stream);
-    printmsg(printer, *p.msg, f->ref.msg, stream);
+    upb_text_push(printer, fd->name, stream);
+    printmsg(printer, *p.msg, stream);
     upb_text_pop(printer, stream);
   } else {
-    upb_text_printfield(printer, *fd->name, f->type, upb_deref(p, f->type), stream);
+    upb_text_printfield(printer, fd->name, f->type, upb_deref(p, f->type), stream);
   }
 }
 
-void upb_msg_print(void *data, struct upb_msgdef *m, bool single_line,
-                   FILE *stream)
+void upb_msg_print(struct upb_msg *msg, bool single_line, FILE *stream)
 {
   struct upb_text_printer printer;
   upb_text_printer_init(&printer, single_line);
-  printmsg(&printer, data, m, stream);
+  printmsg(&printer, msg, stream);
 }
diff --git a/src/upb_msg.h b/src/upb_msg.h
index 6a0568aaee..e2b69038f0 100644
--- a/src/upb_msg.h
+++ b/src/upb_msg.h
@@ -108,6 +108,18 @@ INLINE struct google_protobuf_FieldDescriptorProto *upb_msg_field_descriptor(
   return m->field_descriptors[f->field_index];
 }
 
+/* Message structure. *********************************************************/
+
+struct upb_msg {
+  struct upb_msgdef *def;
+  void *gptr;  /* Generic pointer for use by subclasses. */
+  uint8_t data[1];
+};
+
+INLINE void *upb_msg_gptr(struct upb_msg *msg) {
+  return msg->gptr;
+}
+
 /* Field access. **************************************************************/
 
 /* Note that these only provide access to fields that are directly in the msg
@@ -115,14 +127,16 @@ INLINE struct google_protobuf_FieldDescriptorProto *upb_msg_field_descriptor(
  * necessary to dereference the returned values. */
 
 /* Returns a pointer to a specific field in a message. */
-INLINE union upb_value_ptr upb_msg_getptr(void *msg, struct upb_msg_fielddef *f) {
+INLINE union upb_value_ptr upb_msg_getptr(struct upb_msg *msg,
+                                          struct upb_msg_fielddef *f) {
   union upb_value_ptr p;
-  p._void = ((char*)msg + f->byte_offset);
+  p._void = &msg->data[f->byte_offset];
   return p;
 }
 
 /* Returns a a specific field in a message. */
-INLINE union upb_value upb_msg_get(void *msg, struct upb_msg_fielddef *f) {
+INLINE union upb_value upb_msg_get(struct upb_msg *msg,
+                                   struct upb_msg_fielddef *f) {
   return upb_deref(upb_msg_getptr(msg, f), f->type);
 }
 
@@ -145,40 +159,40 @@ INLINE uint8_t upb_isset_mask(uint32_t field_index) {
 }
 
 /* Returns true if the given field is set, false otherwise. */
-INLINE void upb_msg_set(void *msg, struct upb_msg_fielddef *f)
+INLINE void upb_msg_set(struct upb_msg *msg, struct upb_msg_fielddef *f)
 {
-  ((char*)msg)[upb_isset_offset(f->field_index)] |= upb_isset_mask(f->field_index);
+  msg->data[upb_isset_offset(f->field_index)] |= upb_isset_mask(f->field_index);
 }
 
 /* Clears the set bit for this field in the given message. */
-INLINE void upb_msg_unset(void *msg, struct upb_msg_fielddef *f)
+INLINE void upb_msg_unset(struct upb_msg *msg, struct upb_msg_fielddef *f)
 {
-  ((char*)msg)[upb_isset_offset(f->field_index)] &= ~upb_isset_mask(f->field_index);
+  msg->data[upb_isset_offset(f->field_index)] &= ~upb_isset_mask(f->field_index);
 }
 
 /* Tests whether the given field is set. */
-INLINE bool upb_msg_isset(void *msg, struct upb_msg_fielddef *f)
+INLINE bool upb_msg_isset(struct upb_msg *msg, struct upb_msg_fielddef *f)
 {
-  return ((char*)msg)[upb_isset_offset(f->field_index)] & upb_isset_mask(f->field_index);
+  return msg->data[upb_isset_offset(f->field_index)] & upb_isset_mask(f->field_index);
 }
 
 /* Returns true if *all* required fields are set, false otherwise. */
-INLINE bool upb_msg_all_required_fields_set(void *msg, struct upb_msgdef *m)
+INLINE bool upb_msg_all_required_fields_set(struct upb_msg *msg, struct upb_msgdef *m)
 {
   int num_fields = m->num_required_fields;
   int i = 0;
   while(num_fields > 8) {
-    if(((uint8_t*)msg)[i++] != 0xFF) return false;
+    if(msg->data[i++] != 0xFF) return false;
     num_fields -= 8;
   }
-  if(((uint8_t*)msg)[i] != (1 << num_fields) - 1) return false;
+  if(msg->data[i] != (1 << num_fields) - 1) return false;
   return true;
 }
 
 /* Clears the set bit for all fields. */
-INLINE void upb_msg_clear(void *msg, struct upb_msgdef *m)
+INLINE void upb_msg_clear(struct upb_msg *msg)
 {
-  memset(msg, 0, m->set_flags_bytes);
+  memset(msg->data, 0, msg->def->set_flags_bytes);
 }
 
 /* Number->field and name->field lookup.  *************************************/
@@ -230,12 +244,12 @@ INLINE struct upb_msg_fielddef *upb_msg_fieldbyname(struct upb_msgdef *m,
  * new message data to hold it.  If byref is set, strings in the returned
  * upb_msg will reference s instead of copying from it, but this requires that
  * s will live for as long as the returned message does. */
-void *upb_msg_parsenew(struct upb_msgdef *m, struct upb_string *s);
+struct upb_msg *upb_msg_parsenew(struct upb_msgdef *m, struct upb_string *s);
 
 /* This function should be used to free messages that were parsed with
  * upb_msg_parsenew.  It will free the message appropriately (including all
  * submessages). */
-void upb_msg_free(void *msg, struct upb_msgdef *m);
+void upb_msg_free(struct upb_msg *msg);
 
 
 /* Parsing with (re)allocation callbacks. *************************************/
@@ -243,56 +257,52 @@ void upb_msg_free(void *msg, struct upb_msgdef *m);
 /* This interface parses protocol buffers into upb_msgs, but allows the client
  * to supply allocation callbacks whenever the parser needs to obtain a string,
  * array, or submsg (a "dynamic field").  If the parser sees that a dynamic
- * field is already present (its "set bit" is set) it will use that, otherwise
- * it will call the allocation callback to obtain one.
+ * field is already present (its "set bit" is set) it will use that, resizing
+ * it if necessary in the case of an array.  Otherwise it will call the
+ * allocation callback to obtain one.
  *
  * This may seem trivial (since nearly all clients will use malloc and free for
  * memory management), but the allocation callback can be used for more than
  * just allocation.  If we are parsing data into an existing upb_msg, the
  * allocation callback can examine any existing memory that is allocated for
  * the dynamic field and determine whether it can reuse it.  It can also
- * perform memory management like unrefing the existing field or refing the new.
+ * perform memory management like refing the new field.
  *
  * This parser is layered on top of the event-based parser in upb_parse.h.  The
  * parser is upb_mm_msg.h is layered on top of this parser.
  *
  * This parser is fully streaming-capable. */
 
-typedef struct upb_array *(*upb_msg_getarray_cb_t)(
-    void *msg, struct upb_msgdef *m,
-    struct upb_array *existingval, struct upb_msg_fielddef *f,
-    upb_arraylen_t size);
+/* Should return an initialized array. */
+typedef struct upb_array *(*upb_msg_getandref_array_cb_t)(
+    void *from_gptr, struct upb_array *existingval, struct upb_msg_fielddef *f);
 
-/* Callback to allocate a string of size >=len.  If len==0 then the client can
- * assume that the parser intends to reference the memory instead of copying
- * it. */
-typedef struct upb_string *(*upb_msg_getstring_cb_t)(
-    void *msg, struct upb_msgdef *m,
-    struct upb_string *existingval, struct upb_msg_fielddef *f, size_t len);
+/* Callback to allocate a string.  If byref is true, the client should assume
+ * that the string will be referencing the input data. */
+typedef struct upb_string *(*upb_msg_getandref_string_cb_t)(
+    void *from_gptr, struct upb_string *existingval, struct upb_msg_fielddef *f,
+    bool byref);
 
-typedef void *(*upb_msg_getmsg_cb_t)(
-    void *msg, struct upb_msgdef *m,
-    void *existingval, struct upb_msg_fielddef *f);
+/* Should return a cleared message. */
+typedef struct upb_msg *(*upb_msg_getandref_msg_cb_t)(
+    void *from_gptr, struct upb_msg *existingval, struct upb_msg_fielddef *f);
 
 struct upb_msg_parser_frame {
-  struct upb_msgdef *m;
-  void *msg;
+  struct upb_msg *msg;
 };
 
 struct upb_msg_parser {
   struct upb_stream_parser s;
   bool merge;
   bool byref;
-  struct upb_msg *m;
   struct upb_msg_parser_frame stack[UPB_MAX_NESTING], *top;
-  upb_msg_getarray_cb_t getarray_cb;
-  upb_msg_getstring_cb_t getstring_cb;
-  upb_msg_getmsg_cb_t getmsg_cb;
+  upb_msg_getandref_array_cb_t getarray_cb;
+  upb_msg_getandref_string_cb_t getstring_cb;
+  upb_msg_getandref_msg_cb_t getmsg_cb;
 };
 
 void upb_msg_parser_reset(struct upb_msg_parser *p,
-                          void *msg, struct upb_msgdef *m,
-                          bool byref);
+                          struct upb_msg *msg, bool byref);
 
 /* Parses protocol buffer data out of data which has length of len.  The data
  * need not be a complete protocol buffer.  The number of bytes parsed is
@@ -347,9 +357,8 @@ upb_status_t upb_msg_serialize(struct upb_msg_serialize_state *s,
 
 /* Text dump  *****************************************************************/
 
-bool upb_msg_eql(void *data1, void *data2, struct upb_msgdef *m, bool recursive);
-void upb_msg_print(void *data, struct upb_msgdef *m, bool single_line,
-                   FILE *stream);
+bool upb_msg_eql(struct upb_msg *msg1, struct upb_msg *msg2, bool recursive);
+void upb_msg_print(struct upb_msg *data, bool single_line, FILE *stream);
 
 /* Internal functions. ********************************************************/
 
diff --git a/src/upb_string.c b/src/upb_string.c
index bb40a626ff..7754936741 100644
--- a/src/upb_string.c
+++ b/src/upb_string.c
@@ -14,8 +14,8 @@ bool upb_strreadfile(const char *filename, struct upb_string *data) {
   long size = ftell(f);
   if(size < 0) return false;
   if(fseek(f, 0, SEEK_SET) != 0) return false;
-  data->ptr = (char*)malloc(size);
   data->byte_len = size;
+  upb_stralloc(data, data->byte_len);
   if(fread(data->ptr, size, 1, f) != 1) {
     free(data->ptr);
     return false;
diff --git a/src/upb_string.h b/src/upb_string.h
index 528c8c8c13..7b63f1c6c5 100644
--- a/src/upb_string.h
+++ b/src/upb_string.h
@@ -37,6 +37,7 @@ extern "C" {
 #define INLINE static inline
 #endif
 
+#define UPB_MAX(x, y) ((x) > (y) ? (x) : (y))
 #define UPB_MIN(x, y) ((x) < (y) ? (x) : (y))
 
 struct upb_string {
@@ -44,45 +45,80 @@ struct upb_string {
    * ingrained convention that we follow it. */
   char *ptr;
   uint32_t byte_len;
+  uint32_t byte_size;  /* How many bytes of ptr we own. */
 };
 
+INLINE void upb_strinit(struct upb_string *str)
+{
+  str->ptr = NULL;
+  str->byte_len = 0;
+  str->byte_size = 0;
+}
+
+INLINE void upb_struninit(struct upb_string *str)
+{
+  if(str->byte_size) free(str->ptr);
+}
+
+INLINE struct upb_string *upb_strnew()
+{
+  struct upb_string *str = (struct upb_string*)malloc(sizeof(*str));
+  upb_strinit(str);
+  return str;
+}
+
+INLINE void upb_strfree(struct upb_string *str)
+{
+  upb_struninit(str);
+  free(str);
+}
+
+INLINE void upb_stralloc(struct upb_string *str, uint32_t size)
+{
+  if(str->byte_size < size) {
+    /* Need to resize. */
+    str->byte_size = size;
+    void *oldptr = str->byte_size == 0 ? NULL : str->ptr;
+    str->ptr = (char*)realloc(oldptr, str->byte_size);
+  }
+}
+
+INLINE void upb_strdrop(struct upb_string *str)
+{
+  upb_struninit(str);
+}
+
 INLINE bool upb_streql(struct upb_string *s1, struct upb_string *s2) {
   return s1->byte_len == s2->byte_len &&
          memcmp(s1->ptr, s2->ptr, s1->byte_len) == 0;
 }
 
-INLINE int upb_strcmp(struct upb_string s1, struct upb_string s2) {
-  size_t common_length = UPB_MIN(s1.byte_len, s2.byte_len);
-  int common_diff = memcmp(s1.ptr, s2.ptr, common_length);
-  if(common_diff == 0) return s1.byte_len - s2.byte_len;
-  else return common_diff;
+INLINE int upb_strcmp(struct upb_string *s1, struct upb_string *s2) {
+  size_t common_length = UPB_MIN(s1->byte_len, s2->byte_len);
+  int common_diff = memcmp(s1->ptr, s2->ptr, common_length);
+  return common_diff == 0 ? (int)s1->byte_len - (int)s2->byte_len : common_diff;
 }
 
 INLINE void upb_strcpy(struct upb_string *dest, struct upb_string *src) {
-  memcpy(dest->ptr, src->ptr, src->byte_len);
   dest->byte_len = src->byte_len;
+  upb_stralloc(dest, dest->byte_len);
+  memcpy(dest->ptr, src->ptr, src->byte_len);
 }
 
-INLINE struct upb_string upb_strdup(struct upb_string s) {
-  struct upb_string copy;
-  copy.ptr = (char*)malloc(s.byte_len);
-  copy.byte_len = s.byte_len;
-  memcpy(copy.ptr, s.ptr, s.byte_len);
+INLINE struct upb_string *upb_strdup(struct upb_string *s) {
+  struct upb_string *copy = upb_strnew();
+  upb_strcpy(copy, s);
   return copy;
 }
 
-INLINE struct upb_string upb_strdupc(char *s) {
-  struct upb_string copy;
-  copy.byte_len = strlen(s);
-  copy.ptr = (char*)malloc(copy.byte_len);
-  memcpy(copy.ptr, s, copy.byte_len);
+INLINE struct upb_string *upb_strdupc(char *s) {
+  struct upb_string *copy = upb_strnew();
+  copy->byte_len = strlen(s);
+  upb_stralloc(copy, copy->byte_len);
+  memcpy(copy->ptr, s, copy->byte_len);
   return copy;
 }
 
-INLINE void upb_strfree(struct upb_string s) {
-  free(s.ptr);
-}
-
 /* Reads an entire file into a newly-allocated string. */
 bool upb_strreadfile(const char *filename, struct upb_string *data);
 
@@ -95,7 +131,7 @@ bool upb_strreadfile(const char *filename, struct upb_string *data);
 /* Allows using upb_strings in printf, ie:
  *   struct upb_string str = UPB_STRLIT("Hello, World!\n");
  *   printf("String is: " UPB_STRFMT, UPB_STRARG(str)); */
-#define UPB_STRARG(str) (str).byte_len, (str).ptr
+#define UPB_STRARG(str) (str)->byte_len, (str)->ptr
 #define UPB_STRFMT "%.*s"
 
 #ifdef __cplusplus
diff --git a/src/upb_text.c b/src/upb_text.c
index 6e1777750e..c9aad7e1b2 100644
--- a/src/upb_text.c
+++ b/src/upb_text.c
@@ -36,7 +36,7 @@ void upb_text_printval(upb_field_type_t type, union upb_value val, FILE *file)
     case GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_TYPE_STRING:
     case GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_TYPE_BYTES:
       /* TODO: escaping. */
-      fprintf(file, "\"" UPB_STRFMT "\"", UPB_STRARG(*val.str)); break;
+      fprintf(file, "\"" UPB_STRFMT "\"", UPB_STRARG(val.str)); break;
   }
 }
 
@@ -48,7 +48,7 @@ static void print_indent(struct upb_text_printer *p, FILE *stream)
 }
 
 void upb_text_printfield(struct upb_text_printer *p,
-                         struct upb_string name,
+                         struct upb_string *name,
                          upb_field_type_t valtype, union upb_value val,
                          FILE *stream)
 {
@@ -62,7 +62,7 @@ void upb_text_printfield(struct upb_text_printer *p,
 }
 
 void upb_text_push(struct upb_text_printer *p,
-                   struct upb_string submsg_type,
+                   struct upb_string *submsg_type,
                    FILE *stream)
 {
   print_indent(p, stream);
diff --git a/src/upb_text.h b/src/upb_text.h
index f35f8d84d6..32d72784a7 100644
--- a/src/upb_text.h
+++ b/src/upb_text.h
@@ -23,10 +23,10 @@ INLINE void upb_text_printer_init(struct upb_text_printer *p, bool single_line)
   p->single_line = single_line;
 }
 void upb_text_printval(upb_field_type_t type, union upb_value p, FILE *file);
-void upb_text_printfield(struct upb_text_printer *p, struct upb_string name,
+void upb_text_printfield(struct upb_text_printer *p, struct upb_string *name,
                          upb_field_type_t valtype, union upb_value val,
                          FILE *stream);
-void upb_text_push(struct upb_text_printer *p, struct upb_string submsg_type,
+void upb_text_push(struct upb_text_printer *p, struct upb_string *submsg_type,
                    FILE *stream);
 void upb_text_pop(struct upb_text_printer *p, FILE *stream);
 
diff --git a/tests/test_table.cc b/tests/test_table.cc
index f61a85c461..1289fbc30c 100644
--- a/tests/test_table.cc
+++ b/tests/test_table.cc
@@ -96,7 +96,7 @@ void test_inttable(int32_t *keys, size_t num_entries)
   upb_inttable_init(&table, num_entries, sizeof(struct inttable_entry));
   for(size_t i = 0; i < num_entries; i++) {
     int32_t key = keys[i];
-    largest_key = max(largest_key, key);
+    largest_key = UPB_MAX((int32_t)largest_key, key);
     struct inttable_entry e;
     e.e.key = key;
     e.value = key*2;
diff --git a/tools/upbc.c b/tools/upbc.c
index f593ae9c41..f9890c616e 100644
--- a/tools/upbc.c
+++ b/tools/upbc.c
@@ -5,8 +5,6 @@
  * easier to understand, but by its nature it is doing some very "meta"
  * kinds of things.
  *
- * TODO: compiler currently has memory leaks (trivial to fix with valgrind).
- *
  * Copyright (c) 2009 Joshua Haberman.  See LICENSE for details.
  */
 
@@ -22,19 +20,19 @@
  * the string (and thus never need to re-allocate). */
 
 /* Convert to C identifier: foo.bar.Baz -> foo_bar_Baz. */
-static void to_cident(struct upb_string str)
+static void to_cident(struct upb_string *str)
 {
-  for(uint32_t i = 0; i < str.byte_len; i++)
-    if(str.ptr[i] == '.' || str.ptr[i] == '/')
-      str.ptr[i] = '_';
+  for(uint32_t i = 0; i < str->byte_len; i++)
+    if(str->ptr[i] == '.' || str->ptr[i] == '/')
+      str->ptr[i] = '_';
 }
 
 /* Convert to C proprocessor identifier: foo.bar.Baz -> FOO_BAR_BAZ. */
-static void to_preproc(struct upb_string str)
+static void to_preproc(struct upb_string *str)
 {
   to_cident(str);
-  for(uint32_t i = 0; i < str.byte_len; i++)
-    str.ptr[i] = toupper(str.ptr[i]);
+  for(uint32_t i = 0; i < str->byte_len; i++)
+    str->ptr[i] = toupper(str->ptr[i]);
 }
 
 static int memrchr(char *data, char c, size_t len)
@@ -64,7 +62,7 @@ static void write_h(struct upb_symtab_entry *entries[], int num_entries,
                     char *outfile_name, char *descriptor_cident, FILE *stream)
 {
   /* Header file prologue. */
-  struct upb_string include_guard_name = upb_strdupc(outfile_name);
+  struct upb_string *include_guard_name = upb_strdupc(outfile_name);
   to_preproc(include_guard_name);
   fputs("/* This file was generated by upbc (the upb compiler).  "
         "Do not edit. */\n\n", stream),
@@ -90,21 +88,21 @@ static void write_h(struct upb_symtab_entry *entries[], int num_entries,
     struct upb_enum *e = entry->ref._enum;
     google_protobuf_EnumDescriptorProto *ed = e->descriptor;
     /* We use entry->e.key (the fully qualified name) instead of ed->name. */
-    struct upb_string enum_name = upb_strdup(entry->e.key);
+    struct upb_string *enum_name = upb_strdup(&entry->e.key);
     to_cident(enum_name);
 
-    struct upb_string enum_val_prefix = upb_strdup(entry->e.key);
-    enum_val_prefix.byte_len = memrchr(enum_val_prefix.ptr,
+    struct upb_string *enum_val_prefix = upb_strdup(&entry->e.key);
+    enum_val_prefix->byte_len = memrchr(enum_val_prefix->ptr,
                                        UPB_SYMBOL_SEPARATOR,
-                                       enum_val_prefix.byte_len);
-    enum_val_prefix.byte_len++;
+                                       enum_val_prefix->byte_len);
+    enum_val_prefix->byte_len++;
     to_preproc(enum_val_prefix);
 
     fprintf(stream, "typedef enum " UPB_STRFMT " {\n", UPB_STRARG(enum_name));
     if(ed->set_flags.has.value) {
       for(uint32_t j = 0; j < ed->value->len; j++) {  /* Foreach enum value. */
         google_protobuf_EnumValueDescriptorProto *v = ed->value->elements[j];
-        struct upb_string value_name = upb_strdup(*v->name);
+        struct upb_string *value_name = upb_strdup(v->name);
         to_preproc(value_name);
         /* "  GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_TYPE_UINT32 = 13," */
         fprintf(stream, "  " UPB_STRFMT UPB_STRFMT " = %" PRIu32,
@@ -128,7 +126,7 @@ static void write_h(struct upb_symtab_entry *entries[], int num_entries,
     if(entries[i]->type != UPB_SYM_MESSAGE) continue;
     struct upb_symtab_entry *entry = entries[i];
     /* We use entry->e.key (the fully qualified name). */
-    struct upb_string msg_name = upb_strdup(entry->e.key);
+    struct upb_string *msg_name = upb_strdup(&entry->e.key);
     to_cident(msg_name);
     fprintf(stream, "struct " UPB_STRFMT ";\n", UPB_STRARG(msg_name));
     fprintf(stream, "typedef struct " UPB_STRFMT "\n    " UPB_STRFMT ";\n\n",
@@ -143,9 +141,11 @@ static void write_h(struct upb_symtab_entry *entries[], int num_entries,
     struct upb_symtab_entry *entry = entries[i];
     struct upb_msgdef *m = entry->ref.msg;
     /* We use entry->e.key (the fully qualified name). */
-    struct upb_string msg_name = upb_strdup(entry->e.key);
+    struct upb_string *msg_name = upb_strdup(&entry->e.key);
     to_cident(msg_name);
     fprintf(stream, "struct " UPB_STRFMT " {\n", UPB_STRARG(msg_name));
+    fputs("  struct upb_msgdef *def;\n", stream);
+    fputs("  void *gptr;\n", stream);
     fputs("  union {\n", stream);
     fprintf(stream, "    uint8_t bytes[%" PRIu32 "];\n", m->set_flags_bytes);
     fputs("    struct {\n", stream);
@@ -153,7 +153,7 @@ static void write_h(struct upb_symtab_entry *entries[], int num_entries,
       static char* labels[] = {"", "optional", "required", "repeated"};
       struct google_protobuf_FieldDescriptorProto *fd = m->field_descriptors[j];
       fprintf(stream, "      bool " UPB_STRFMT ":1;  /* = %" PRIu32 ", %s. */\n",
-              UPB_STRARG(*fd->name), fd->number, labels[fd->label]);
+              UPB_STRARG(fd->name), fd->number, labels[fd->label]);
     }
     fputs("    } has;\n", stream);
     fputs("  } set_flags;\n", stream);
@@ -170,14 +170,14 @@ static void write_h(struct upb_symtab_entry *entries[], int num_entries,
           type_name_ref.ptr++;
           type_name_ref.byte_len--;
         }
-        struct upb_string type_name = upb_strdup(type_name_ref);
+        struct upb_string *type_name = upb_strdup(&type_name_ref);
         to_cident(type_name);
         if(f->label == GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_LABEL_REPEATED) {
           fprintf(stream, "  UPB_MSG_ARRAY(" UPB_STRFMT ")* " UPB_STRFMT ";\n",
-                  UPB_STRARG(type_name), UPB_STRARG(*fd->name));
+                  UPB_STRARG(type_name), UPB_STRARG(fd->name));
         } else {
           fprintf(stream, "  " UPB_STRFMT "* " UPB_STRFMT ";\n",
-                  UPB_STRARG(type_name), UPB_STRARG(*fd->name));
+                  UPB_STRARG(type_name), UPB_STRARG(fd->name));
         }
         upb_strfree(type_name);
       } else if(f->label == GOOGLE_PROTOBUF_FIELDDESCRIPTORPROTO_LABEL_REPEATED) {
@@ -193,7 +193,7 @@ static void write_h(struct upb_symtab_entry *entries[], int num_entries,
           "struct upb_int64_array*"
         };
         fprintf(stream, "  %s " UPB_STRFMT ";\n",
-                c_types[fd->type], UPB_STRARG(*fd->name));
+                c_types[fd->type], UPB_STRARG(fd->name));
       } else {
         static char* c_types[] = {
           "", "double", "float", "int64_t", "uint64_t", "int32_t", "uint64_t",
@@ -202,7 +202,7 @@ static void write_h(struct upb_symtab_entry *entries[], int num_entries,
           "int32_t", "int64_t"
         };
         fprintf(stream, "  %s " UPB_STRFMT ";\n",
-                c_types[fd->type], UPB_STRARG(*fd->name));
+                c_types[fd->type], UPB_STRARG(fd->name));
       }
     }
     fputs("};\n", stream);
@@ -230,7 +230,7 @@ struct strtable_entry {
 struct typetable_entry {
   struct upb_strtable_entry e;
   struct upb_msg_fielddef *field;
-  struct upb_string cident;  /* Type name converted with to_cident(). */
+  struct upb_string *cident;  /* Type name converted with to_cident(). */
   /* A list of all values of this type, in an established order. */
   union upb_value *values;
   int values_size, values_len;
@@ -251,7 +251,7 @@ struct msgtable_entry {
 int compare_entries(const void *_e1, const void *_e2)
 {
   struct strtable_entry *const*e1 = _e1, *const*e2 = _e2;
-  return upb_strcmp((*e1)->e.key, (*e2)->e.key);
+  return upb_strcmp(&(*e1)->e.key, &(*e2)->e.key);
 }
 
 /* Mutually recursive functions to recurse over a set of possibly nested
@@ -297,7 +297,6 @@ static void add_strings_from_msg(void *data, struct upb_msgdef *m,
  *
  * TODO: make these use a generic msg visitor. */
 
-
 struct typetable_entry *get_or_insert_typeentry(struct upb_strtable *t,
                                                 struct upb_msg_fielddef *f)
 {
@@ -306,7 +305,7 @@ struct typetable_entry *get_or_insert_typeentry(struct upb_strtable *t,
   struct typetable_entry *type_e = upb_strtable_lookup(t, &type_name);
   if(type_e == NULL) {
     struct typetable_entry new_type_e = {
-      .e = {.key = type_name}, .field = f, .cident = upb_strdup(type_name),
+      .e = {.key = type_name}, .field = f, .cident = upb_strdup(&type_name),
       .values = NULL, .values_size = 0, .values_len = 0,
       .arrays = NULL, .arrays_size = 0, .arrays_len = 0
     };
@@ -323,7 +322,7 @@ static void add_value(union upb_value value, struct upb_msg_fielddef *f,
 {
   struct typetable_entry *type_e = get_or_insert_typeentry(t, f);
   if(type_e->values_len == type_e->values_size) {
-    type_e->values_size = max(type_e->values_size * 2, 4);
+    type_e->values_size = UPB_MAX(type_e->values_size * 2, 4);
     type_e->values = realloc(type_e->values, sizeof(*type_e->values) * type_e->values_size);
   }
   type_e->values[type_e->values_len++] = value;
@@ -343,7 +342,7 @@ static void add_submsgs(void *data, struct upb_msgdef *m, struct upb_strtable *t
       struct typetable_entry *arr_type_e =
           get_or_insert_typeentry(t, f);
       if(arr_type_e->arrays_len == arr_type_e->arrays_size) {
-        arr_type_e->arrays_size = max(arr_type_e->arrays_size * 2, 4);
+        arr_type_e->arrays_size = UPB_MAX(arr_type_e->arrays_size * 2, 4);
         arr_type_e->arrays = realloc(arr_type_e->arrays,
                                      sizeof(*arr_type_e->arrays)*arr_type_e->arrays_size);
       }
@@ -492,7 +491,7 @@ static void write_message_c(void *data, struct upb_msgdef *m,
         for(unsigned int j = 0; j < m->num_fields; j++) {
           struct upb_msg_fielddef *f = &m->fields[j];
           google_protobuf_FieldDescriptorProto *fd = m->field_descriptors[j];
-          fprintf(stream, "    ." UPB_STRFMT " = ", UPB_STRARG(*fd->name));
+          fprintf(stream, "    ." UPB_STRFMT " = ", UPB_STRARG(fd->name));
           if(upb_msg_isset(msgdata, f))
             fprintf(stream, "true");
           else
@@ -505,7 +504,7 @@ static void write_message_c(void *data, struct upb_msgdef *m,
           struct upb_msg_fielddef *f = &m->fields[j];
           google_protobuf_FieldDescriptorProto *fd = m->field_descriptors[j];
           union upb_value val = upb_msg_get(msgdata, f);
-          fprintf(stream, "    ." UPB_STRFMT " = ", UPB_STRARG(*fd->name));
+          fprintf(stream, "    ." UPB_STRFMT " = ", UPB_STRARG(fd->name));
           if(!upb_msg_isset(msgdata, f)) {
             fputs("0,   /* Not set. */", stream);
           } else if(upb_isstring(f)) {
@@ -516,7 +515,7 @@ static void write_message_c(void *data, struct upb_msgdef *m,
               struct strtable_entry *str_e = upb_strtable_lookup(&strings, val.str);
               assert(str_e);
               fprintf(stream, "&strings[%d],   /* \"" UPB_STRFMT "\" */",
-                      str_e->num, UPB_STRARG(*val.str));
+                      str_e->num, UPB_STRARG(val.str));
             }
           } else if(upb_isarray(f)) {
             /* Find this submessage in the list of msgs for that type. */
@@ -642,15 +641,15 @@ int main(int argc, char *argv[])
   if(!outfile_base) outfile_base = input_file;
 
   /* Read input file. */
-  struct upb_string descriptor;
-  if(!upb_strreadfile(input_file, &descriptor))
+  struct upb_string *descriptor = upb_strnew();
+  if(!upb_strreadfile(input_file, descriptor))
     error("Couldn't read input file.");
 
   /* Parse input file. */
   struct upb_context c;
   upb_context_init(&c);
-  google_protobuf_FileDescriptorSet *fds =
-      upb_msg_parsenew(c.fds_msg, &descriptor);
+  struct upb_msg *fds_msg = upb_msg_parsenew(c.fds_msg, descriptor);
+  google_protobuf_FileDescriptorSet *fds = (void*)fds_msg;
   if(!fds)
     error("Failed to parse input file descriptor.");
   if(!upb_context_addfds(&c, fds))
@@ -686,7 +685,7 @@ int main(int argc, char *argv[])
     write_message_c(fds, c.fds_msg, cident, h_filename, argc, argv, input_file, c_file);
     fclose(c_file);
   }
-  upb_msg_free(fds, c.fds_msg);
+  upb_msg_free(fds_msg);
   upb_context_free(&c);
   upb_strfree(descriptor);
   fclose(h_file);