Applied changes from google3.

bazel/upb_proto_library.bzl

@@ -120,6 +120,9 @@ _WrappedGeneratedSrcsInfo = provider(fields = ["srcs"])
 _WrappedDefsGeneratedSrcsInfo = provider(fields = ["srcs"])
 
 def _compile_upb_protos(ctx, proto_info, proto_sources, ext):
+    if len(proto_sources) == 0:
+        return GeneratedSrcsInfo(srcs = [], hdrs = [])
+
     srcs = [_generate_output_file(ctx, name, ext + ".c") for name in proto_sources]
     hdrs = [_generate_output_file(ctx, name, ext + ".h") for name in proto_sources]
     transitive_sets = proto_info.transitive_descriptor_sets.to_list()

tests/test_cpp.cc

@@ -50,7 +50,7 @@ static const int kExpectedHandlerData = 1232323;
 
 class StringBufTesterBase {
  public:
-  static const int kFieldNumber = 3;
+  static constexpr int kFieldNumber = 3;
 
   StringBufTesterBase() : seen_(false), handler_data_val_(0) {}
 
@@ -286,7 +286,7 @@ class StartMsgTesterBase {
  public:
   // We don't need the FieldDef it will create, but the test harness still
   // requires that we provide one.
-  static const int kFieldNumber = 3;
+  static constexpr int kFieldNumber = 3;
 
   StartMsgTesterBase() : seen_(false), handler_data_val_(0) {}
 
@@ -437,7 +437,7 @@ class StartMsgTesterBoolMethodWithHandlerData : public StartMsgTesterBase {
 
 class Int32ValueTesterBase {
  public:
-  static const int kFieldNumber = 1;
+  static constexpr int kFieldNumber = 1;
 
   Int32ValueTesterBase() : seen_(false), val_(0), handler_data_val_(0) {}
 

upb/handlers.h

@@ -106,7 +106,7 @@ typedef struct {
 #define UPB_HANDLERATTR_INIT {NULL, NULL, NULL, false}
 
 /* Bufhandle, data passed along with a buffer to indicate its provenance. */
-typedef struct {
+struct upb_bufhandle {
   /* The beginning of the buffer.  This may be different than the pointer
    * passed to a StringBuf handler because the handler may receive data
    * that is from the middle or end of a larger buffer. */
@@ -133,7 +133,9 @@ typedef struct {
                                             : NULL;
   }
 #endif
-} upb_bufhandle;
+};
+
+typedef struct upb_bufhandle upb_bufhandle;
 
 #define UPB_BUFHANDLE_INIT {NULL, 0, NULL, NULL}
 

upbc/generator.cc

@@ -281,7 +281,9 @@ std::string FieldDefault(const protobuf::FieldDescriptor* field) {
     case protobuf::FieldDescriptor::CPPTYPE_BOOL:
       return field->default_value_bool() ? "true" : "false";
     case protobuf::FieldDescriptor::CPPTYPE_ENUM:
-      return EnumValueSymbol(field->default_value_enum());
+      // Use a number instead of a symbolic name so that we don't require
+      // this enum's header to be included.
+      return absl::StrCat(field->default_value_enum()->number());
   }
   ABSL_ASSERT(false);
   return "XXX";