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Fix msan false positive in the swiss table #2092

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Fix msan false positive in the swiss table #2092

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15 changes: 15 additions & 0 deletions absl/container/internal/container_memory.h
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Original file line number Diff line number Diff line change
Expand Up @@ -479,6 +479,21 @@ struct map_slot_policy {
_Pragma("GCC diagnostic pop")
#define ABSL_SWISSTABLE_IGNORE_UNINITIALIZED_RETURN(x) \
ABSL_SWISSTABLE_IGNORE_UNINITIALIZED(return x)
#elif defined(ABSL_HAVE_MEMORY_SANITIZER)
// Unlike GCC's -Wmaybe-uninitialized (a compile-time diagnostic),
// MemorySanitizer is a runtime tool and reports these intentional reads of
// possibly-uninitialized values (e.g. slot_array for empty tables). Mark the
// storage initialized so MSan does not flag them, preserving value/reference
// category for the various accessors. SanitizerUnpoisonMemoryRegion is a no-op
// unless a sanitizer is enabled.
template <typename T>
inline T&& SwisstableIgnoreUninitialized(T&& value) {
SanitizerUnpoisonMemoryRegion(&value, sizeof(value));
return static_cast<T&&>(value);
}
#define ABSL_SWISSTABLE_IGNORE_UNINITIALIZED(x) x
#define ABSL_SWISSTABLE_IGNORE_UNINITIALIZED_RETURN(x) \
return SwisstableIgnoreUninitialized(x)
#else
#define ABSL_SWISSTABLE_IGNORE_UNINITIALIZED(x) x
#define ABSL_SWISSTABLE_IGNORE_UNINITIALIZED_RETURN(x) return x
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