Do eager parsing when building descriptors.

Lazy parsing can use reflection to verify consistency, and reflection while building descriptors causes deadlock.

PiperOrigin-RevId: 555238461

src/google/protobuf/descriptor.cc

@@ -81,6 +81,7 @@
 #include "google/protobuf/generated_message_util.h"
 #include "google/protobuf/io/strtod.h"
 #include "google/protobuf/io/tokenizer.h"
+#include "google/protobuf/parse_context.h"
 #include "google/protobuf/port.h"
 #include "google/protobuf/repeated_ptr_field.h"
 #include "google/protobuf/text_format.h"
@@ -5249,11 +5250,9 @@ typename DescriptorT::OptionsType* DescriptorBuilder::AllocateOptionsImpl(
     return nullptr;
   }
 
-  // Avoid using MergeFrom()/CopyFrom() in this class to make it -fno-rtti
+  const bool parse_success =
-  // friendly. Without RTTI, MergeFrom() and CopyFrom() will fallback to the
+      internal::ParseNoReflection(orig_options.SerializeAsString(), *options);
-  // reflection based method, which requires the Descriptor. However, we are in
+  ABSL_DCHECK(parse_success);
-  // the middle of building the descriptors, thus the deadlock.
-  options->ParseFromString(orig_options.SerializeAsString());
 
   // Don't add to options_to_interpret_ unless there were uninterpreted
   // options.  This not only avoids unnecessary work, but prevents a
@@ -9424,6 +9423,16 @@ void LazyDescriptor::Once(const ServiceDescriptor* service) {
   }
 }
 
+bool ParseNoReflection(absl::string_view from, google::protobuf::MessageLite& to) {
+  to.Clear();
+  const char* ptr;
+  internal::ParseContext ctx(io::CodedInputStream::GetDefaultRecursionLimit(),
+                             false, &ptr, from);
+  ptr = to._InternalParse(ptr, &ctx);
+  if (ptr == nullptr || !ctx.EndedAtLimit()) return false;
+  return to.IsInitializedWithErrors();
+}
+
 namespace cpp {
 bool HasPreservingUnknownEnumSemantics(const FieldDescriptor* field) {
   if (field->legacy_enum_field_treated_as_closed()) {

src/google/protobuf/descriptor.h

@@ -123,6 +123,9 @@ class UninterpretedOption;
 class FeatureSet;
 class SourceCodeInfo;
 
+// Defined in message_lite.h
+class MessageLite;
+
 // Defined in message.h
 class Message;
 class Reflection;
@@ -2830,6 +2833,13 @@ struct FieldRangeImpl {
   const T* descriptor;
 };
 
+// While building descriptors, we need to avoid using MergeFrom()/CopyFrom() to
+// be -fno-rtti friendly. Without RTTI, MergeFrom() and CopyFrom() will fallback
+// to the reflection based method, which requires the Descriptor. However, while
+// building the descriptors, this causes deadlock. We also must disable lazy
+// parsing because that uses reflection to verify consistency.
+bool ParseNoReflection(absl::string_view from, google::protobuf::MessageLite& to);
+
 // The context for these functions under `cpp` is "for the C++ implementation".
 // In particular, questions like "does this field have a has bit?" have a
 // different answer depending on the language.

src/google/protobuf/descriptor_database.cc

@@ -888,7 +888,9 @@ bool EncodedDescriptorDatabase::FindAllFileNames(
 bool EncodedDescriptorDatabase::MaybeParse(
     std::pair<const void*, int> encoded_file, FileDescriptorProto* output) {
   if (encoded_file.first == nullptr) return false;
-  return output->ParseFromArray(encoded_file.first, encoded_file.second);
+  absl::string_view source(static_cast<const char*>(encoded_file.first),
+                           encoded_file.second);
+  return internal::ParseNoReflection(source, *output);
 }
 
 EncodedDescriptorDatabase::EncodedDescriptorDatabase()