diff --color -Naur protobuf-c-1.5.2.orig/protoc-gen-c/c_bytes_field.cc protobuf-c-1.5.2/protoc-gen-c/c_bytes_field.cc
--- protobuf-c-1.5.2.orig/protoc-gen-c/c_bytes_field.cc	2025-02-02 12:19:55.000000000 +0800
+++ protobuf-c-1.5.2/protoc-gen-c/c_bytes_field.cc	2026-02-26 14:39:48.281836089 +0800
@@ -94,19 +94,15 @@
 
 void BytesFieldGenerator::GenerateStructMembers(google::protobuf::io::Printer* printer) const
 {
-  switch (descriptor_->label()) {
-    case google::protobuf::FieldDescriptor::LABEL_REQUIRED:
+  if (descriptor_->is_required())
       printer->Print(variables_, "ProtobufCBinaryData $name$$deprecated$;\n");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_OPTIONAL:
+  else if (!descriptor_->is_repeated()) {
       if (descriptor_->containing_oneof() == NULL && FieldSyntax(descriptor_) == 2)
         printer->Print(variables_, "protobuf_c_boolean has_$name$$deprecated$;\n");
       printer->Print(variables_, "ProtobufCBinaryData $name$$deprecated$;\n");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_REPEATED:
+  } else {
       printer->Print(variables_, "size_t n_$name$$deprecated$;\n");
       printer->Print(variables_, "ProtobufCBinaryData *$name$$deprecated$;\n");
-      break;
   }
 }
 void BytesFieldGenerator::GenerateDefaultValueDeclarations(google::protobuf::io::Printer* printer) const
@@ -135,20 +131,15 @@
 }
 void BytesFieldGenerator::GenerateStaticInit(google::protobuf::io::Printer* printer) const
 {
-  switch (descriptor_->label()) {
-    case google::protobuf::FieldDescriptor::LABEL_REQUIRED:
+  if (descriptor_->is_required())
       printer->Print(variables_, "$default_value$");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_OPTIONAL:
+  else if (!descriptor_->is_repeated()) {
       if (FieldSyntax(descriptor_) == 2)
         printer->Print(variables_, "0, ");
       printer->Print(variables_, "$default_value$");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_REPEATED:
+  } else
       // no support for default?
       printer->Print("0,NULL");
-      break;
-  }
 }
 void BytesFieldGenerator::GenerateDescriptorInitializer(google::protobuf::io::Printer* printer) const
 {
diff --color -Naur protobuf-c-1.5.2.orig/protoc-gen-c/c_enum_field.cc protobuf-c-1.5.2/protoc-gen-c/c_enum_field.cc
--- protobuf-c-1.5.2.orig/protoc-gen-c/c_enum_field.cc	2025-04-07 09:17:27.000000000 +0800
+++ protobuf-c-1.5.2/protoc-gen-c/c_enum_field.cc	2026-02-26 14:41:23.091570453 +0800
@@ -95,19 +95,15 @@
 
 void EnumFieldGenerator::GenerateStructMembers(google::protobuf::io::Printer* printer) const
 {
-  switch (descriptor_->label()) {
-    case google::protobuf::FieldDescriptor::LABEL_REQUIRED:
+  if (descriptor_->is_required())
       printer->Print(variables_, "$type$ $name$$deprecated$;\n");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_OPTIONAL:
+  else if (!descriptor_->is_repeated()) {
       if (descriptor_->containing_oneof() == NULL && FieldSyntax(descriptor_) == 2)
         printer->Print(variables_, "protobuf_c_boolean has_$name$$deprecated$;\n");
       printer->Print(variables_, "$type$ $name$$deprecated$;\n");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_REPEATED:
+  } else {
       printer->Print(variables_, "size_t n_$name$$deprecated$;\n");
       printer->Print(variables_, "$type$ *$name$$deprecated$;\n");
-      break;
   }
 }
 
@@ -117,20 +113,15 @@
 }
 void EnumFieldGenerator::GenerateStaticInit(google::protobuf::io::Printer* printer) const
 {
-  switch (descriptor_->label()) {
-    case google::protobuf::FieldDescriptor::LABEL_REQUIRED:
+  if (descriptor_->is_required())
       printer->Print(variables_, "$default$");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_OPTIONAL:
+  else if (!descriptor_->is_repeated()) {
       if (FieldSyntax(descriptor_) == 2)
         printer->Print(variables_, "0, ");
       printer->Print(variables_, "$default$");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_REPEATED:
+  } else
       // no support for default?
       printer->Print("0,NULL");
-      break;
-  }
 }
 
 void EnumFieldGenerator::GenerateDescriptorInitializer(google::protobuf::io::Printer* printer) const
diff --color -Naur protobuf-c-1.5.2.orig/protoc-gen-c/c_field.cc protobuf-c-1.5.2/protoc-gen-c/c_field.cc
--- protobuf-c-1.5.2.orig/protoc-gen-c/c_field.cc	2025-04-07 09:17:27.000000000 +0800
+++ protobuf-c-1.5.2/protoc-gen-c/c_field.cc	2026-02-26 14:51:18.897583300 +0800
@@ -125,11 +125,11 @@
     variables["oneofname"] = CamelToLower(oneof->name());
 
   if (FieldSyntax(descriptor_) == 3 &&
-    descriptor_->label() == google::protobuf::FieldDescriptor::LABEL_OPTIONAL) {
+    !descriptor_->is_required() && !descriptor_->is_repeated()) {
     variables["LABEL"] = "NONE";
     optional_uses_has = false;
   } else {
-    variables["LABEL"] = CamelToUpper(GetLabelName(descriptor_->label()));
+    variables["LABEL"] = CamelToUpper(GetLabelName(*descriptor_));
   }
 
   if (descriptor_->has_default_value()) {
@@ -145,11 +145,11 @@
 
   variables["flags"] = "0";
 
-  if (descriptor_->label() == google::protobuf::FieldDescriptor::LABEL_REPEATED
+  if (descriptor_->is_repeated()
    && is_packable_type (descriptor_->type())
    && descriptor_->options().packed()) {
     variables["flags"] += " | PROTOBUF_C_FIELD_FLAG_PACKED";
-  } else if (descriptor_->label() == google::protobuf::FieldDescriptor::LABEL_REPEATED
+  } else if (descriptor_->is_repeated()
    && is_packable_type (descriptor_->type())
    && FieldSyntax(descriptor_) == 3
    && !descriptor_->options().has_packed()) {
@@ -179,11 +179,9 @@
     "  $value$,\n"
     "  PROTOBUF_C_LABEL_$LABEL$,\n"
     "  PROTOBUF_C_TYPE_$TYPE$,\n");
-  switch (descriptor_->label()) {
-    case google::protobuf::FieldDescriptor::LABEL_REQUIRED:
+  if (descriptor_->is_required())
       printer->Print(variables, "  0,   /* quantifier_offset */\n");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_OPTIONAL:
+  else if (!descriptor_->is_repeated()) {
       if (oneof != NULL) {
         printer->Print(variables, "  offsetof($classname$, $oneofname$_case),\n");
       } else if (optional_uses_has) {
@@ -191,11 +189,8 @@
       } else {
 	printer->Print(variables, "  0,   /* quantifier_offset */\n");
       }
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_REPEATED:
+  } else
       printer->Print(variables, "  offsetof($classname$, n_$name$),\n");
-      break;
-  }
   printer->Print(variables, "  offsetof($classname$, $name$),\n");
   printer->Print(variables, "  $descriptor_addr$,\n");
   printer->Print(variables, "  $default_value$,\n");
diff --color -Naur protobuf-c-1.5.2.orig/protoc-gen-c/c_helpers.cc protobuf-c-1.5.2/protoc-gen-c/c_helpers.cc
--- protobuf-c-1.5.2.orig/protoc-gen-c/c_helpers.cc	2025-04-07 09:17:27.000000000 +0800
+++ protobuf-c-1.5.2/protoc-gen-c/c_helpers.cc	2026-02-26 14:45:50.717133480 +0800
@@ -329,13 +329,10 @@
   return result;
 }
 
-std::string GetLabelName(google::protobuf::FieldDescriptor::Label label) {
-  switch (label) {
-    case google::protobuf::FieldDescriptor::LABEL_OPTIONAL: return "optional";
-    case google::protobuf::FieldDescriptor::LABEL_REQUIRED: return "required";
-    case google::protobuf::FieldDescriptor::LABEL_REPEATED: return "repeated";
-  }
-  return "bad-label";
+std::string GetLabelName(const google::protobuf::FieldDescriptor &desc) {
+  if (desc.is_required()) return "required";
+  if (desc.is_repeated()) return "repeated";
+  return "optional";
 }
 
 unsigned
diff --color -Naur protobuf-c-1.5.2.orig/protoc-gen-c/c_helpers.h protobuf-c-1.5.2/protoc-gen-c/c_helpers.h
--- protobuf-c-1.5.2.orig/protoc-gen-c/c_helpers.h	2025-04-07 09:17:27.000000000 +0800
+++ protobuf-c-1.5.2/protoc-gen-c/c_helpers.h	2026-02-26 14:44:54.189606880 +0800
@@ -151,7 +151,7 @@
 std::string FilenameIdentifier(compat::StringView filename);
 
 // return 'required', 'optional', or 'repeated'
-std::string GetLabelName(google::protobuf::FieldDescriptor::Label label);
+std::string GetLabelName(const google::protobuf::FieldDescriptor &desc);
 
 // write IntRanges entries for a bunch of sorted values.
 // returns the number of ranges there are to bsearch.
diff --color -Naur protobuf-c-1.5.2.orig/protoc-gen-c/c_message_field.cc protobuf-c-1.5.2/protoc-gen-c/c_message_field.cc
--- protobuf-c-1.5.2.orig/protoc-gen-c/c_message_field.cc	2025-02-02 12:19:55.000000000 +0800
+++ protobuf-c-1.5.2/protoc-gen-c/c_message_field.cc	2026-02-26 14:51:47.040015109 +0800
@@ -83,15 +83,11 @@
   vars["name"] = FieldName(descriptor_);
   vars["type"] = FullNameToC(descriptor_->message_type()->full_name(), descriptor_->message_type()->file());
   vars["deprecated"] = FieldDeprecated(descriptor_);
-  switch (descriptor_->label()) {
-    case google::protobuf::FieldDescriptor::LABEL_REQUIRED:
-    case google::protobuf::FieldDescriptor::LABEL_OPTIONAL:
+  if (!descriptor_->is_repeated())
       printer->Print(vars, "$type$ *$name$$deprecated$;\n");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_REPEATED:
+  else {
       printer->Print(vars, "size_t n_$name$$deprecated$;\n");
       printer->Print(vars, "$type$ **$name$$deprecated$;\n");
-      break;
   }
 }
 std::string MessageFieldGenerator::GetDefaultValue(void) const
@@ -103,15 +99,10 @@
 }
 void MessageFieldGenerator::GenerateStaticInit(google::protobuf::io::Printer* printer) const
 {
-  switch (descriptor_->label()) {
-    case google::protobuf::FieldDescriptor::LABEL_REQUIRED:
-    case google::protobuf::FieldDescriptor::LABEL_OPTIONAL:
+  if (!descriptor_->is_repeated())
       printer->Print("NULL");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_REPEATED:
+  else
       printer->Print("0,NULL");
-      break;
-  }
 }
 void MessageFieldGenerator::GenerateDescriptorInitializer(google::protobuf::io::Printer* printer) const
 {
diff --color -Naur protobuf-c-1.5.2.orig/protoc-gen-c/c_primitive_field.cc protobuf-c-1.5.2/protoc-gen-c/c_primitive_field.cc
--- protobuf-c-1.5.2.orig/protoc-gen-c/c_primitive_field.cc	2025-04-07 09:17:27.000000000 +0800
+++ protobuf-c-1.5.2/protoc-gen-c/c_primitive_field.cc	2026-02-26 14:49:28.569229580 +0800
@@ -109,19 +109,15 @@
   vars["name"] = FieldName(descriptor_);
   vars["deprecated"] = FieldDeprecated(descriptor_);
 
-  switch (descriptor_->label()) {
-    case google::protobuf::FieldDescriptor::LABEL_REQUIRED:
+  if (descriptor_->is_required())
       printer->Print(vars, "$c_type$ $name$$deprecated$;\n");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_OPTIONAL:
+  else if (!descriptor_->is_repeated()) {
       if (descriptor_->containing_oneof() == NULL && FieldSyntax(descriptor_) == 2)
         printer->Print(vars, "protobuf_c_boolean has_$name$$deprecated$;\n");
       printer->Print(vars, "$c_type$ $name$$deprecated$;\n");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_REPEATED:
+  } else {
       printer->Print(vars, "size_t n_$name$$deprecated$;\n");
       printer->Print(vars, "$c_type$ *$name$$deprecated$;\n");
-      break;
   }
 }
 std::string PrimitiveFieldGenerator::GetDefaultValue() const
@@ -156,19 +152,14 @@
   } else {
     vars["default_value"] = "0";
   }
-  switch (descriptor_->label()) {
-    case google::protobuf::FieldDescriptor::LABEL_REQUIRED:
+  if (descriptor_->is_required())
       printer->Print(vars, "$default_value$");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_OPTIONAL:
+  else if (!descriptor_->is_repeated()) {
       if (FieldSyntax(descriptor_) == 2)
         printer->Print(vars, "0, ");
       printer->Print(vars, "$default_value$");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_REPEATED:
+  } else
       printer->Print("0,NULL");
-      break;
-  }
 }
 
 void PrimitiveFieldGenerator::GenerateDescriptorInitializer(google::protobuf::io::Printer* printer) const
diff --color -Naur protobuf-c-1.5.2.orig/protoc-gen-c/c_string_field.cc protobuf-c-1.5.2/protoc-gen-c/c_string_field.cc
--- protobuf-c-1.5.2.orig/protoc-gen-c/c_string_field.cc	2025-02-02 12:19:55.000000000 +0800
+++ protobuf-c-1.5.2/protoc-gen-c/c_string_field.cc	2026-02-26 14:47:14.151990719 +0800
@@ -94,19 +94,15 @@
 {
   const ProtobufCFileOptions opt = descriptor_->file()->options().GetExtension(pb_c_file);
 
-  switch (descriptor_->label()) {
-    case google::protobuf::FieldDescriptor::LABEL_REQUIRED:
-    case google::protobuf::FieldDescriptor::LABEL_OPTIONAL:
+  if (!descriptor_->is_repeated()) {
       if (opt.const_strings())
         printer->Print(variables_, "const ");
       printer->Print(variables_, "char *$name$$deprecated$;\n");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_REPEATED:
+  } else {
       printer->Print(variables_, "size_t n_$name$$deprecated$;\n");
       if (opt.const_strings())
         printer->Print(variables_, "const ");
       printer->Print(variables_, "char **$name$$deprecated$;\n");
-      break;
   }
 }
 void StringFieldGenerator::GenerateDefaultValueDeclarations(google::protobuf::io::Printer* printer) const
@@ -138,15 +134,10 @@
   } else {
     vars["default"] = "(char *)protobuf_c_empty_string";
   }
-  switch (descriptor_->label()) {
-    case google::protobuf::FieldDescriptor::LABEL_REQUIRED:
-    case google::protobuf::FieldDescriptor::LABEL_OPTIONAL:
+  if (!descriptor_->is_repeated())
       printer->Print(vars, "$default$");
-      break;
-    case google::protobuf::FieldDescriptor::LABEL_REPEATED:
+  else
       printer->Print(vars, "0,NULL");
-      break;
-  }
 }
 void StringFieldGenerator::GenerateDescriptorInitializer(google::protobuf::io::Printer* printer) const
 {