Mark LazyField as zero initializable.

PiperOrigin-RevId: 645141554

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

@@ -147,6 +147,7 @@ FieldGeneratorBase::FieldGeneratorBase(const FieldDescriptor* field,
   }
 
   has_trivial_zero_default_ = CanInitializeByZeroing(field, options, scc);
+  has_brace_default_assign_ = has_trivial_zero_default_ && !is_lazy_;
 }
 
 void FieldGeneratorBase::GenerateMemberConstexprConstructor(

src/google/protobuf/compiler/cpp/field.h

@@ -69,6 +69,9 @@ class FieldGeneratorBase {
   // I.e., the field can be initialized with `memset(&field, 0, sizeof(field))`
   bool has_trivial_zero_default() const { return has_trivial_zero_default_; }
 
+  // Returns true if the provided field can be initialized with `= {}`.
+  bool has_brace_default_assign() const { return has_brace_default_assign_; }
+
   // Returns true if the field is a singular or repeated message.
   // This includes group message types. To explicitly check if a message
   // type is a group type, use the `is_group()` function,
@@ -204,6 +207,7 @@ class FieldGeneratorBase {
   bool is_trivial_ = false;
   bool has_trivial_value_ = false;
   bool has_trivial_zero_default_ = false;
+  bool has_brace_default_assign_ = false;
   bool is_message_ = false;
   bool is_group_ = false;
   bool is_string_ = false;
@@ -255,6 +259,9 @@ class FieldGenerator {
   bool has_trivial_zero_default() const {
     return impl_->has_trivial_zero_default();
   }
+  bool has_brace_default_assign() const {
+    return impl_->has_brace_default_assign();
+  }
   bool is_message() const { return impl_->is_message(); }
   bool is_group() const { return impl_->is_group(); }
   bool is_weak() const { return impl_->is_weak(); }

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

@@ -332,9 +332,7 @@ bool CanInitializeByZeroing(const FieldDescriptor* field,
     case FieldDescriptor::CPPTYPE_BOOL:
       return field->default_value_bool() == false;
     case FieldDescriptor::CPPTYPE_MESSAGE:
-      // Non-repeated, non-lazy message fields are raw pointers initialized to
-      // null.
-      return !IsLazy(field, options, scc_analyzer);
+      return true;
     default:
       return false;
   }
@@ -446,7 +444,7 @@ std::string ResolveKeyword(absl::string_view name) {
 }
 
 std::string DotsToColons(absl::string_view name) {
-  std::vector<std::string> scope = absl::StrSplit(name, ".", absl::SkipEmpty());
+  std::vector<std::string> scope = absl::StrSplit(name, '.', absl::SkipEmpty());
   for (auto& word : scope) {
     word = ResolveKeyword(word);
   }

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

@@ -2470,7 +2470,8 @@ void MessageGenerator::GenerateZeroInitFields(io::Printer* p) const {
   auto emit_pending_zero_fields = [&](Iterator end) {
     if (first != nullptr) {
       const FieldDescriptor* last = end[-1];
-      if (first != last) {
+      if (first != last ||
+          !field_generators_.get(first).has_brace_default_assign()) {
         p->Emit({{"first", FieldName(first)},
                  {"last", FieldName(last)},
                  {"Impl", "Impl_"},

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

@@ -73,12 +73,9 @@ static void OptimizeLayoutHelper(std::vector<const FieldDescriptor*>* fields,
   enum Family {
     REPEATED = 0,
     STRING = 1,
-    // Laying out LAZY_MESSAGE before MESSAGE allows a single memset to zero
-    // MESSAGE and ZERO_INITIALIZABLE fields together.
-    LAZY_MESSAGE = 2,
-    MESSAGE = 3,
-    ZERO_INITIALIZABLE = 4,
-    OTHER = 5,
+    MESSAGE = 2,
+    ZERO_INITIALIZABLE = 3,
+    OTHER = 4,
     kMaxFamily
   };
 
@@ -96,9 +93,6 @@ static void OptimizeLayoutHelper(std::vector<const FieldDescriptor*>* fields,
       f = STRING;
     } else if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
       f = MESSAGE;
-      if (IsLazy(field, options, scc_analyzer)) {
-        f = LAZY_MESSAGE;
-      }
     } else if (CanInitializeByZeroing(field, options, scc_analyzer)) {
       f = ZERO_INITIALIZABLE;
     }
@@ -192,9 +186,6 @@ static void OptimizeLayoutHelper(std::vector<const FieldDescriptor*>* fields,
 // STRING is grouped next, as our Clear/SharedCtor/SharedDtor walks it and
 // calls ArenaStringPtr::Destroy on each.
 //
-// LAZY_MESSAGE is grouped next, as it interferes with the ability to memset
-// non-repeated fields otherwise.
-//
 // MESSAGE is grouped next, as our Clear/SharedDtor code walks it and calls
 // delete on each.  We initialize these fields with a NULL pointer (see
 // MessageFieldGenerator::GenerateConstructorCode), which allows them to be