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Return empty string for out-of-range values in dense enum name lookup. #29255

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Return empty string for out-of-range values in dense enum name lookup. #29255

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17 changes: 12 additions & 5 deletions src/google/protobuf/generated_message_reflection.h
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Original file line number Diff line number Diff line change
Expand Up @@ -347,11 +347,18 @@ const std::string& NameOfDenseEnum(int v) {
static_assert(max_val - min_val >= 0, "Too many enums between min and max.");
static DenseEnumCacheInfo deci = {/* once_flag */ {}, /* atomic ptr */ {},
min_val, max_val, descriptor_fn};
if (ABSL_PREDICT_TRUE(v >= min_val && v <= max_val)) {
const std::string** cache = deci.cache.load(std::memory_order_acquire);
if (ABSL_PREDICT_TRUE(cache != nullptr)) {
return *cache[v - min_val];
}
if (ABSL_PREDICT_FALSE(v < min_val || v > max_val)) {
// Prevent the compiler from pre-loading the empty string.
// Otherwise, it adds an instruction to every in-bounds-call (adding ~5%
// to cpu).
// We expect to see many more in-bounds calls than out-of-bounds calls, so
// this is a net win.
ABSL_BLOCK_TAIL_CALL_OPTIMIZATION();
return GetEmptyStringAlreadyInited();
}
const std::string** cache = deci.cache.load(std::memory_order_acquire);
if (ABSL_PREDICT_TRUE(cache != nullptr)) {
return *cache[v - min_val];
}
return NameOfDenseEnumSlow(v, &deci);
}
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