diff --git a/tools/upbc.c b/tools/upbc.c
index fa264d7eda..b22b9587d7 100644
--- a/tools/upbc.c
+++ b/tools/upbc.c
@@ -221,6 +221,7 @@ int compare_entries(const void *_e1, const void *_e2)
 static void write_c(struct upb_symtab_entry *entries[], int num_entries,
                     char *hfile_name, char *outfile_name, FILE *stream)
 {
+  (void)outfile_name;
   fputs("/* This file was generated by upbc (the upb compiler).  "
         "Do not edit. */\n\n", stream),
   fprintf(stream, "#include \"%s\"\n\n", hfile_name);
@@ -236,7 +237,6 @@ static void write_c(struct upb_symtab_entry *entries[], int num_entries,
 
   upb_strtable_init(&t, 16, sizeof(struct strtable_entry));
   for(int i = 0; i < num_entries; i++) {
-    //addident(entries[i].key);
     struct strtable_entry e = {.e = {.key = entries[i]->e.key}};
     if(upb_strtable_lookup(&t, &e.e.key) == NULL) upb_strtable_insert(&t, &e.e);
     switch(entries[i]->type) {
@@ -296,9 +296,60 @@ static void write_c(struct upb_symtab_entry *entries[], int num_entries,
   fputs("static struct upb_string strings[] = {\n", stream);
   for(int i = 0; i < size; i++) {
     struct strtable_entry *e = str_entries[i];
-    fprintf(stream, "  {.ptr = &strdata[%d], .byte_len=%d}", e->offset, e->e.key.byte_len);
-    if(i+1 != size) fputc(',', stream);
-    fputc('\n', stream);
+    fprintf(stream, "  {.ptr = &strdata[%d], .byte_len=%d},\n", e->offset, e->e.key.byte_len);
+  }
+  fputs("};\n\n", stream);
+
+  /* Emit fields. */
+  fputs("static google_protobuf_FieldDescriptorProto fields[] = {\n", stream);
+  int total = 0;
+  for(int i = 0; i < num_entries; i++) {
+    if(entries[i]->type != UPB_SYM_MESSAGE) continue;
+    struct upb_msg *m = entries[i]->ref.msg;
+    for(uint32_t j = 0; j < m->num_fields; j++) {
+      struct google_protobuf_FieldDescriptorProto *fd = m->field_descriptors[j];
+      struct strtable_entry *e = upb_strtable_lookup(&t, fd->name);
+      fprintf(stream, "  {.set_flags = {.bytes={0x%02hhx}}, .name=&strings[%3d], .number=%d, .label=%d, .type=%2d, .type_name=NULL},\n",
+              fd->set_flags.bytes[0], e->num, fd->number, fd->label, fd->type);
+      total ++;
+    }
+  }
+  fputs("};\n\n", stream);
+
+  fputs("static google_protobuf_FieldDescriptorProto *field_pointers[] = {\n", stream);
+  for(int i = 0; i < total; i++) {
+    fprintf(stream, "  &fields[%d],\n", i);
+  }
+  fputs("};\n\n", stream);
+
+  offset = 0;
+  fputs("static UPB_MSG_ARRAY(google_protobuf_FieldDescriptorProto) field_arrays[] = {\n", stream);
+  for(int i = 0; i < num_entries; i++) {
+    if(entries[i]->type != UPB_SYM_MESSAGE) continue;
+    struct upb_msg *m = entries[i]->ref.msg;
+    fprintf(stream, "  {.elements=&field_pointers[%d], .len=%d},\n", offset, m->num_fields);
+    offset += m->num_fields;
+  }
+  fputs("};\n\n", stream);
+
+  /* Emit messages. */
+  fputs("static google_protobuf_DescriptorProto messages[] = {\n", stream);
+  offset = 0;
+  for(int i = 0; i < num_entries; i++) {
+    if(entries[i]->type != UPB_SYM_MESSAGE) continue;
+    struct upb_msg *m = entries[i]->ref.msg;
+    struct google_protobuf_DescriptorProto *d = m->descriptor;
+    struct strtable_entry *e = upb_strtable_lookup(&t, d->name);
+    fprintf(stream, "  {.set_flags = {.bytes={0x%02hhx}}, .name=&strings[%3d], .field=&field_arrays[%d]},\n",
+            d->set_flags.bytes[0], e->num, offset);
+  }
+  fputs("};\n\n", stream);
+
+  fputs("static google_protobuf_DescriptorProto *message_pointers[] = {\n", stream);
+  offset = 0;
+  for(int i = 0; i < num_entries; i++) {
+    if(entries[i]->type != UPB_SYM_MESSAGE) continue;
+    fprintf(stream, "  &messages[%d],\n", offset);
   }
   fputs("};\n\n", stream);
 }