Addressed PR comments.

upb/decode.c

@@ -461,7 +461,9 @@ static const char *decode_fixed_packed(upb_decstate *d, const char *ptr,
   decode_reserve(d, arr, count);
   void *mem = UPB_PTR_AT(_upb_array_ptr(arr), arr->len << lg2, void);
   arr->len += count;
-  memcpy(mem, ptr, val->size);  /* XXX: ptr boundary. */
+  // Note: if/when the decoder supports multi-buffer input, we will need to
+  // handle buffer seams here.
+  memcpy(mem, ptr, val->size);
   return ptr + val->size;
 }
 

upb/def.c

@@ -2363,7 +2363,7 @@ static void create_service(
   }
 }
 
-static int popcount(uint64_t x) {
+static int count_bits_debug(uint64_t x) {
   // For assertions only, speed does not matter.
   int n = 0;
   while (x) {
@@ -2387,17 +2387,20 @@ upb_enumlayout *create_enumlayout(symtab_addctx *ctx, const upb_enumdef *e) {
   }
 
   int32_t *values = symtab_alloc(ctx, sizeof(*values) * n);
-  int32_t *p = values;
 
-  for (int i = 0; i < e->value_count; i++) {
+  if (n) {
-    int32_t val = e->values[i].number;
+    int32_t *p = values;
-    if ((uint32_t)val >= 64) {
+
-      *p++ = val;
+    for (int i = 0; i < e->value_count; i++) {
+      int32_t val = e->values[i].number;
+      if ((uint32_t)val >= 64) {
+        *p++ = val;
+      }
     }
+    UPB_ASSERT(p == values + n);
   }
 
-  UPB_ASSERT(p == values + n);
+  UPB_ASSERT(upb_inttable_count(&e->iton) == n + count_bits_debug(mask));
-  UPB_ASSERT(upb_inttable_count(&e->iton) == n + popcount(mask));
 
   upb_enumlayout *layout = symtab_alloc(ctx, sizeof(*layout));
   layout->value_count = n;
@@ -2407,6 +2410,34 @@ upb_enumlayout *create_enumlayout(symtab_addctx *ctx, const upb_enumdef *e) {
   return layout;
 }
 
+static void create_enumvaldef(
+    symtab_addctx *ctx, const char *prefix,
+    const google_protobuf_EnumValueDescriptorProto *val_proto, upb_enumdef *e,
+    int i) {
+  upb_enumvaldef *val = (upb_enumvaldef *)&e->values[i];
+  upb_strview name = google_protobuf_EnumValueDescriptorProto_name(val_proto);
+  upb_value v = upb_value_constptr(val);
+
+  val->enum_ = e;  /* Must happen prior to symtab_add(). */
+  val->full_name = makefullname(ctx, prefix, name);
+  val->number = google_protobuf_EnumValueDescriptorProto_number(val_proto);
+  symtab_add(ctx, val->full_name, pack_def(val, UPB_DEFTYPE_ENUMVAL));
+
+  SET_OPTIONS(val->opts, EnumValueDescriptorProto, EnumValueOptions, val_proto);
+
+  if (i == 0 && e->file->syntax == UPB_SYNTAX_PROTO3 && val->number != 0) {
+    symtab_errf(ctx, "for proto3, the first enum value must be zero (%s)",
+                e->full_name);
+  }
+
+  CHK_OOM(upb_strtable_insert(&e->ntoi, name.data, name.size, v, ctx->arena));
+
+  // Multiple enumerators can have the same number, first one wins.
+  if (!upb_inttable_lookup(&e->iton, val->number, NULL)) {
+    CHK_OOM(upb_inttable_insert(&e->iton, val->number, v, ctx->arena));
+  }
+}
+
 static void create_enumdef(
     symtab_addctx *ctx, const char *prefix,
     const google_protobuf_EnumDescriptorProto *enum_proto,
@@ -2442,29 +2473,7 @@ static void create_enumdef(
   SET_OPTIONS(e->opts, EnumDescriptorProto, EnumOptions, enum_proto);
 
   for (i = 0; i < n; i++) {
-    const google_protobuf_EnumValueDescriptorProto *val_proto = values[i];
+    create_enumvaldef(ctx, prefix, values[i], e, i);
-    upb_enumvaldef *val = (upb_enumvaldef*)&e->values[i];
-    upb_strview name = google_protobuf_EnumValueDescriptorProto_name(val_proto);
-    upb_value v = upb_value_constptr(val);
-
-    val->enum_ = e;  /* Must happen prior to symtab_add(). */
-    val->full_name = makefullname(ctx, prefix, name);
-    val->number = google_protobuf_EnumValueDescriptorProto_number(val_proto);
-    symtab_add(ctx, val->full_name, pack_def(val, UPB_DEFTYPE_ENUMVAL));
-
-    SET_OPTIONS(val->opts, EnumValueDescriptorProto, EnumValueOptions, val_proto);
-
-    if (i == 0 && e->file->syntax == UPB_SYNTAX_PROTO3 && val->number != 0) {
-      symtab_errf(ctx, "for proto3, the first enum value must be zero (%s)",
-                  e->full_name);
-    }
-
-    CHK_OOM(upb_strtable_insert(&e->ntoi, name.data, name.size, v, ctx->arena));
-
-    // Multiple enumerators can have the same number, first one wins.
-    if (!upb_inttable_lookup(&e->iton, val->number, NULL)) {
-      CHK_OOM(upb_inttable_insert(&e->iton, val->number, v, ctx->arena));
-    }
   }
 
   upb_inttable_compact(&e->iton, ctx->arena);
@@ -2473,7 +2482,7 @@ static void create_enumdef(
     if (ctx->layout) {
       UPB_ASSERT(ctx->enum_count < ctx->layout->enum_count);
       e->layout = ctx->layout->enums[ctx->enum_count++];
-      UPB_ASSERT(n == e->layout->value_count + popcount(e->layout->mask));
+      UPB_ASSERT(n == e->layout->value_count + count_bits_debug(e->layout->mask));
     } else {
       e->layout = create_enumlayout(ctx, e);
     }

upbc/protoc-gen-upb.cc

@@ -745,7 +745,7 @@ void WriteHeader(const protobuf::FileDescriptor* file, Output& output) {
   output("\n");
 
   if (file->syntax() == protobuf::FileDescriptor::SYNTAX_PROTO2) {
-    for (auto enumdesc : this_file_enums) {
+    for (const auto* enumdesc : this_file_enums) {
       output("extern const upb_enumlayout $0;\n", EnumInit(enumdesc));
     }
   }