Replace PROTOBUF_ENABLE_FUZZ_MESSAGE_SPACE_USED_LONG macro with constexpr function for easier maintenance.

No semantic change expected.

PiperOrigin-RevId: 675264102

src/google/protobuf/generated_message_reflection.cc

@@ -496,19 +496,19 @@ size_t Reflection::SpaceUsedLong(const Message& message) const {
       }
     }
   }
-#ifndef PROTOBUF_FUZZ_MESSAGE_SPACE_USED_LONG
-  return total_size;
-#else
-  // Use both `this` and `dummy` to generate the seed so that the scale factor
-  // is both per-object and non-predictable, but consistent across multiple
-  // calls in the same binary.
-  static bool dummy;
-  uintptr_t seed =
-      reinterpret_cast<uintptr_t>(&dummy) ^ reinterpret_cast<uintptr_t>(this);
-  // Fuzz the size by +/- 50%.
-  double scale = (static_cast<double>(seed % 10000) / 10000) + 0.5;
-  return total_size * scale;
-#endif
+  if (internal::DebugHardenFuzzMessageSpaceUsedLong()) {
+    // Use both `this` and `dummy` to generate the seed so that the scale factor
+    // is both per-object and non-predictable, but consistent across multiple
+    // calls in the same binary.
+    static bool dummy;
+    uintptr_t seed =
+        reinterpret_cast<uintptr_t>(&dummy) ^ reinterpret_cast<uintptr_t>(this);
+    // Fuzz the size by +/- 50%.
+    double scale = (static_cast<double>(seed % 10000) / 10000) + 0.5;
+    return total_size * scale;
+  } else {
+    return total_size;
+  }
 }
 
 namespace {

src/google/protobuf/port.h

@@ -281,6 +281,10 @@ constexpr bool DebugHardenForceCopyInMove() {
   return false;
 }
 
+constexpr bool DebugHardenFuzzMessageSpaceUsedLong() {
+  return false;
+}
+
 // Returns true if pointers are 8B aligned, leaving least significant 3 bits
 // available.
 inline constexpr bool PtrIsAtLeast8BAligned() { return alignof(void*) >= 8; }

src/google/protobuf/port_def.inc

@@ -398,10 +398,6 @@ static_assert(PROTOBUF_ABSL_MIN(20230125, 3),
 #define PROTOBUF_RESTRICT
 #endif
 
-#ifdef PROTOBUF_FUZZ_MESSAGE_SPACE_USED_LONG
-#error PROTOBUF_FUZZ_MESSAGE_SPACE_USED_LONG was previously defined
-#endif
-
 #ifdef PROTOBUF_FORCE_ALLOCATION_ON_CONSTRUCTION
 #error PROTOBUF_FORCE_ALLOCATION_ON_CONSTRUCTION was previously defined
 #endif

src/google/protobuf/port_undef.inc

@@ -41,7 +41,6 @@
 #undef PROTOC_EXPORT
 #undef PROTOBUF_NODISCARD
 #undef PROTOBUF_RESTRICT
-#undef PROTOBUF_FUZZ_MESSAGE_SPACE_USED_LONG
 #undef PROTOBUF_FORCE_ALLOCATION_ON_CONSTRUCTION
 #undef PROTOBUF_UNUSED
 #undef PROTOBUF_ASSUME