Fix compiler error for empty default ctor for std::atomic<int> variables

src/google/protobuf/compiler/cpp/cpp_enum_field.cc

@@ -496,7 +496,7 @@ void RepeatedEnumFieldGenerator::GenerateConstinitInitializer(
   format("$name$_()");
   if (descriptor_->is_packed() &&
       HasGeneratedMethods(descriptor_->file(), options_)) {
-    format("\n, _$name$_cached_byte_size_()");
+    format("\n, _$name$_cached_byte_size_(0)");
   }
 }
 

src/google/protobuf/compiler/cpp/cpp_primitive_field.cc

@@ -486,7 +486,7 @@ void RepeatedPrimitiveFieldGenerator::GenerateConstinitInitializer(
   format("$name$_()");
   if (descriptor_->is_packed() && FixedSize(descriptor_->type()) == -1 &&
       HasGeneratedMethods(descriptor_->file(), options_)) {
-    format("\n, _$name$_cached_byte_size_()");
+    format("\n, _$name$_cached_byte_size_(0)");
   }
 }
 

src/google/protobuf/descriptor.pb.cc

@@ -393,9 +393,9 @@ PROTOBUF_ATTRIBUTE_NO_DESTROY PROTOBUF_CONSTINIT UninterpretedOptionDefaultTypeI
 constexpr SourceCodeInfo_Location::SourceCodeInfo_Location(
   ::PROTOBUF_NAMESPACE_ID::internal::ConstantInitialized)
   : path_()
-  , _path_cached_byte_size_()
+  , _path_cached_byte_size_(0)
   , span_()
-  , _span_cached_byte_size_()
+  , _span_cached_byte_size_(0)
   , leading_detached_comments_()
   , leading_comments_(&::PROTOBUF_NAMESPACE_ID::internal::fixed_address_empty_string)
   , trailing_comments_(&::PROTOBUF_NAMESPACE_ID::internal::fixed_address_empty_string){}
@@ -423,7 +423,7 @@ PROTOBUF_ATTRIBUTE_NO_DESTROY PROTOBUF_CONSTINIT SourceCodeInfoDefaultTypeIntern
 constexpr GeneratedCodeInfo_Annotation::GeneratedCodeInfo_Annotation(
   ::PROTOBUF_NAMESPACE_ID::internal::ConstantInitialized)
   : path_()
-  , _path_cached_byte_size_()
+  , _path_cached_byte_size_(0)
   , source_file_(&::PROTOBUF_NAMESPACE_ID::internal::fixed_address_empty_string)
   , begin_(0)
   , end_(0){}