Silence -Winvalid-offsetof for cel::common_internal::ReferenceCountedString

PiperOrigin-RevId: 688691954

Author: asedeno

common/internal/reference_count.cc

@@ -60,6 +60,14 @@ class ReferenceCountedStdString final : public ReferenceCounted {
   alignas(std::string) char string_[sizeof(std::string)];
 };
 
+// ReferenceCountedString is non-standard-layout due to having virtual functions
+// from a base class. This causes compilers to warn about the use of offsetof(),
+// but it still works here, so silence the warning and proceed.
+#if defined(__GNUC__) || defined(__clang__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Winvalid-offsetof"
+#endif
+
 class ReferenceCountedString final : public ReferenceCounted {
  public:
   static const ReferenceCountedString* New(const char* data, size_t size) {
@@ -87,6 +95,10 @@ class ReferenceCountedString final : public ReferenceCounted {
   char data_[];
 };
 
+#if defined(__GNUC__) || defined(__clang__)
+#pragma GCC diagnostic pop
+#endif
+
 }  // namespace
 
 std::pair<absl::Nonnull<const ReferenceCount*>, absl::string_view>