From aaece2a98d92d74a6aea999a18e53a66f896e4fc Mon Sep 17 00:00:00 2001
From: Peter Dillinger <peterd@fb.com>
Date: Thu, 4 Jun 2020 15:44:05 -0700
Subject: [PATCH] Fix some defects reported by Coverity Scan (#6933)

Summary:
Confusing checks for null that are never null
Pull Request resolved: https://github.com/facebook/rocksdb/pull/6933

Test Plan: make check

Reviewed By: cheng-chang

Differential Revision: D21885466

Pulled By: pdillinger

fbshipit-source-id: 4b48e03c2a33727f2702b0d12292f9fda5a3c475
---
 db/memtable_list.cc                           | 24 +++++++++----------
 db/memtable_list.h                            |  2 +-
 utilities/transactions/transaction_base.cc    |  6 ++---
 .../transactions/write_prepared_txn_db.cc     |  3 +--
 4 files changed, 15 insertions(+), 20 deletions(-)

diff --git a/db/memtable_list.cc b/db/memtable_list.cc
index 1a23d18cd..acdba0896 100644
--- a/db/memtable_list.cc
+++ b/db/memtable_list.cc
@@ -43,22 +43,20 @@ void MemTableListVersion::UnrefMemTable(autovector<MemTable*>* to_delete,
 }
 
 MemTableListVersion::MemTableListVersion(
-    size_t* parent_memtable_list_memory_usage, MemTableListVersion* old)
+    size_t* parent_memtable_list_memory_usage, const MemTableListVersion& old)
     : max_write_buffer_number_to_maintain_(
-          old->max_write_buffer_number_to_maintain_),
+          old.max_write_buffer_number_to_maintain_),
       max_write_buffer_size_to_maintain_(
-          old->max_write_buffer_size_to_maintain_),
+          old.max_write_buffer_size_to_maintain_),
       parent_memtable_list_memory_usage_(parent_memtable_list_memory_usage) {
-  if (old != nullptr) {
-    memlist_ = old->memlist_;
-    for (auto& m : memlist_) {
-      m->Ref();
-    }
+  memlist_ = old.memlist_;
+  for (auto& m : memlist_) {
+    m->Ref();
+  }
 
-    memlist_history_ = old->memlist_history_;
-    for (auto& m : memlist_history_) {
-      m->Ref();
-    }
+  memlist_history_ = old.memlist_history_;
+  for (auto& m : memlist_history_) {
+    m->Ref();
   }
 }
 
@@ -604,7 +602,7 @@ void MemTableList::InstallNewVersion() {
   } else {
     // somebody else holds the current version, we need to create new one
     MemTableListVersion* version = current_;
-    current_ = new MemTableListVersion(&current_memory_usage_, current_);
+    current_ = new MemTableListVersion(&current_memory_usage_, *version);
     current_->Ref();
     version->Unref();
   }
diff --git a/db/memtable_list.h b/db/memtable_list.h
index bf6750bf2..9991df566 100644
--- a/db/memtable_list.h
+++ b/db/memtable_list.h
@@ -44,7 +44,7 @@ struct FlushJobInfo;
 class MemTableListVersion {
  public:
   explicit MemTableListVersion(size_t* parent_memtable_list_memory_usage,
-                               MemTableListVersion* old = nullptr);
+                               const MemTableListVersion& old);
   explicit MemTableListVersion(size_t* parent_memtable_list_memory_usage,
                                int max_write_buffer_number_to_maintain,
                                int64_t max_write_buffer_size_to_maintain);
diff --git a/utilities/transactions/transaction_base.cc b/utilities/transactions/transaction_base.cc
index 32fb714aa..92b3956e1 100644
--- a/utilities/transactions/transaction_base.cc
+++ b/utilities/transactions/transaction_base.cc
@@ -312,8 +312,7 @@ std::vector<Status> TransactionBaseImpl::MultiGet(
 
   std::vector<Status> stat_list(num_keys);
   for (size_t i = 0; i < num_keys; ++i) {
-    std::string* value = values ? &(*values)[i] : nullptr;
-    stat_list[i] = Get(read_options, column_family[i], keys[i], value);
+    stat_list[i] = Get(read_options, column_family[i], keys[i], &(*values)[i]);
   }
 
   return stat_list;
@@ -350,8 +349,7 @@ std::vector<Status> TransactionBaseImpl::MultiGetForUpdate(
   // TODO(agiardullo): optimize multiget?
   std::vector<Status> stat_list(num_keys);
   for (size_t i = 0; i < num_keys; ++i) {
-    std::string* value = values ? &(*values)[i] : nullptr;
-    stat_list[i] = Get(read_options, column_family[i], keys[i], value);
+    stat_list[i] = Get(read_options, column_family[i], keys[i], &(*values)[i]);
   }
 
   return stat_list;
diff --git a/utilities/transactions/write_prepared_txn_db.cc b/utilities/transactions/write_prepared_txn_db.cc
index 76341d58b..45a192004 100644
--- a/utilities/transactions/write_prepared_txn_db.cc
+++ b/utilities/transactions/write_prepared_txn_db.cc
@@ -294,8 +294,7 @@ std::vector<Status> WritePreparedTxnDB::MultiGet(
 
   std::vector<Status> stat_list(num_keys);
   for (size_t i = 0; i < num_keys; ++i) {
-    std::string* value = values ? &(*values)[i] : nullptr;
-    stat_list[i] = this->Get(options, column_family[i], keys[i], value);
+    stat_list[i] = this->Get(options, column_family[i], keys[i], &(*values)[i]);
   }
   return stat_list;
 }
-- 
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