From b409f8cd859da48c74f9435883d65ffe22ecc884 Mon Sep 17 00:00:00 2001
From: Joshua Haberman <jhaberman@gmail.com>
Date: Thu, 20 Feb 2020 18:53:47 -0800
Subject: [PATCH] Fixed code generator for upbdefs when a file has no messages.

---
 BUILD             | 12 ++++++++++++
 tests/empty.proto |  2 ++
 upbc/generator.cc | 18 ++++++++++++------
 3 files changed, 26 insertions(+), 6 deletions(-)
 create mode 100644 tests/empty.proto

diff --git a/BUILD b/BUILD
index c85ece940b..61601a067e 100644
--- a/BUILD
+++ b/BUILD
@@ -389,11 +389,23 @@ cc_test(
     srcs = ["tests/test_generated_code.c"],
     deps = [
         ":test_messages_proto3_proto_upb",
+        ":empty_upbdefs_proto",
         ":test_upbproto",
         ":upb_test",
     ],
 )
 
+proto_library(
+    name = "empty_proto",
+    srcs = ["tests/empty.proto"],
+)
+
+upb_proto_reflection_library(
+    name = "empty_upbdefs_proto",
+    testonly = 1,
+    deps = [":empty_proto"],
+)
+
 upb_proto_library(
     name = "test_messages_proto3_proto_upb",
     testonly = 1,
diff --git a/tests/empty.proto b/tests/empty.proto
new file mode 100644
index 0000000000..fb45796635
--- /dev/null
+++ b/tests/empty.proto
@@ -0,0 +1,2 @@
+syntax = "proto2";
+
diff --git a/upbc/generator.cc b/upbc/generator.cc
index 50fb42d564..47cc07ad10 100644
--- a/upbc/generator.cc
+++ b/upbc/generator.cc
@@ -853,12 +853,14 @@ void WriteDefSource(const protobuf::FileDescriptor* file, Output& output) {
   }
   output("\n");
 
-  output("static const upb_msglayout *layouts[$0] = {\n", file_messages.size());
-  for (auto message : file_messages) {
-    output("  &$0,\n", MessageInit(message));
+  if (!file_messages.empty()) {
+    output("static const upb_msglayout *layouts[$0] = {\n", file_messages.size());
+    for (auto message : file_messages) {
+      output("  &$0,\n", MessageInit(message));
+    }
+    output("};\n");
+    output("\n");
   }
-  output("};\n");
-  output("\n");
 
   protobuf::FileDescriptorProto file_proto;
   file->CopyTo(&file_proto);
@@ -905,7 +907,11 @@ void WriteDefSource(const protobuf::FileDescriptor* file, Output& output) {
 
   output("upb_def_init $0 = {\n", DefInitSymbol(file));
   output("  deps,\n");
-  output("  layouts,\n");
+  if (file_messages.empty()) {
+    output("  NULL,\n");
+  } else {
+    output("  layouts,\n");
+  }
   output("  \"$0\",\n", file->name());
   output("  UPB_STRVIEW_INIT(descriptor, $0)\n", file_data.size());
   output("};\n");