From 724855c7da07a8519ca1068cceb7d8d380f51815 Mon Sep 17 00:00:00 2001
From: Yi Wu <yiwu@fb.com>
Date: Tue, 29 May 2018 15:11:22 -0700
Subject: [PATCH] Fix LRUCache missing null check on destruct

Summary:
Fix LRUCache missing null check on destruct. The check is needed if LRUCache::DisownData is called.
Closes https://github.com/facebook/rocksdb/pull/3920

Differential Revision: D8191631

Pulled By: yiwu-arbug

fbshipit-source-id: d5014f6e49b51692c18a25fb55ece935f5a023c4
---
 cache/lru_cache.cc | 10 +++++++---
 cache/lru_cache.h  |  2 +-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/cache/lru_cache.cc b/cache/lru_cache.cc
index a128296f9..432fee66d 100644
--- a/cache/lru_cache.cc
+++ b/cache/lru_cache.cc
@@ -474,10 +474,13 @@ LRUCache::LRUCache(size_t capacity, int num_shard_bits,
 }
 
 LRUCache::~LRUCache() {
-  for (int i = 0; i < num_shards_; i++) {
-    shards_[i].~LRUCacheShard();
+  if (shards_ != nullptr) {
+    assert(num_shards_ > 0);
+    for (int i = 0; i < num_shards_; i++) {
+      shards_[i].~LRUCacheShard();
+    }
+    port::cacheline_aligned_free(shards_);
   }
-  port::cacheline_aligned_free(shards_);
 }
 
 CacheShard* LRUCache::GetShard(int shard) {
@@ -504,6 +507,7 @@ void LRUCache::DisownData() {
 // Do not drop data if compile with ASAN to suppress leak warning.
 #ifndef __SANITIZE_ADDRESS__
   shards_ = nullptr;
+  num_shards_ = 0;
 #endif  // !__SANITIZE_ADDRESS__
 }
 
diff --git a/cache/lru_cache.h b/cache/lru_cache.h
index f5219ad35..3c067f0c1 100644
--- a/cache/lru_cache.h
+++ b/cache/lru_cache.h
@@ -295,7 +295,7 @@ class LRUCache : public ShardedCache {
   double GetHighPriPoolRatio();
 
  private:
-  LRUCacheShard* shards_;
+  LRUCacheShard* shards_ = nullptr;
   int num_shards_ = 0;
 };