Move some processing off to a secondary noinline function. This significantly

reduces the stack usage of the recursive function.

PiperOrigin-RevId: 567286733

src/google/protobuf/compiler/parser.cc

@@ -799,25 +799,8 @@ bool Parser::ParseTopLevelStatement(FileDescriptorProto* file,
 // -------------------------------------------------------------------
 // Messages
 
-bool Parser::ParseMessageDefinition(
-    DescriptorProto* message, const LocationRecorder& message_location,
-    const FileDescriptorProto* containing_file) {
-  DO(Consume("message"));
-  {
-    LocationRecorder location(message_location,
-                              DescriptorProto::kNameFieldNumber);
-    location.RecordLegacyLocation(message,
-                                  DescriptorPool::ErrorCollector::NAME);
-    DO(ConsumeIdentifier(message->mutable_name(), "Expected message name."));
-    if (!IsUpperCamelCase(message->name())) {
-      RecordWarning(absl::StrCat(
-          "Message name should be in UpperCamelCase. Found: ", message->name(),
-          ". See https://developers.google.com/protocol-buffers/docs/style"));
-    }
-  }
-  DO(ParseMessageBlock(message, message_location, containing_file));
-
-  if (syntax_identifier_ == "proto3") {
+PROTOBUF_NOINLINE static void GenerateSyntheticOneofs(
+    DescriptorProto* message) {
   // Add synthetic one-field oneofs for optional fields, except messages which
   // already have presence in proto3.
   //
@@ -853,6 +836,28 @@ bool Parser::ParseMessageDefinition(
   }
 }
 
+bool Parser::ParseMessageDefinition(
+    DescriptorProto* message, const LocationRecorder& message_location,
+    const FileDescriptorProto* containing_file) {
+  DO(Consume("message"));
+  {
+    LocationRecorder location(message_location,
+                              DescriptorProto::kNameFieldNumber);
+    location.RecordLegacyLocation(message,
+                                  DescriptorPool::ErrorCollector::NAME);
+    DO(ConsumeIdentifier(message->mutable_name(), "Expected message name."));
+    if (!IsUpperCamelCase(message->name())) {
+      RecordWarning(absl::StrCat(
+          "Message name should be in UpperCamelCase. Found: ", message->name(),
+          ". See https://developers.google.com/protocol-buffers/docs/style"));
+    }
+  }
+  DO(ParseMessageBlock(message, message_location, containing_file));
+
+  if (syntax_identifier_ == "proto3") {
+    GenerateSyntheticOneofs(message);
+  }
+
   return true;
 }