Fix GetCurrentTime() initialization for valgrind

Summary:
Valgrind had false positive complaints about the initialization pattern for `GetCurrentTime()`'s argument in #2480. We can instead have the client initialize the time variable before calling `GetCurrentTime()`, and have `GetCurrentTime()` promise to only overwrite it in success case.
Closes https://github.com/facebook/rocksdb/pull/2526

Differential Revision: D5358689

Pulled By: ajkr

fbshipit-source-id: 857b189f24c19196f6bb299216f3e23e7bc4be42

db/compaction_job.cc

@@ -1283,11 +1283,8 @@ Status CompactionJob::OpenCompactionOutputFile(
   uint64_t output_file_creation_time =
       sub_compact->compaction->MaxInputFileCreationTime();
   if (output_file_creation_time == 0) {
-    int64_t _current_time;
-    auto status = db_options_.env->GetCurrentTime(&_current_time);
-    if (!status.ok()) {
-      _current_time = 0;
-    }
+    int64_t _current_time = 0;
+    db_options_.env->GetCurrentTime(&_current_time);  // ignore error
     output_file_creation_time = static_cast<uint64_t>(_current_time);
   }
 

db/db_impl_open.cc

@@ -854,11 +854,8 @@ Status DBImpl::WriteLevel0TableForRecovery(int job_id, ColumnFamilyData* cfd,
     bool paranoid_file_checks =
         cfd->GetLatestMutableCFOptions()->paranoid_file_checks;
 
-    int64_t _current_time;
-    s = env_->GetCurrentTime(&_current_time);
-    if (!s.ok()) {
-      _current_time = 0;
-    }
+    int64_t _current_time = 0;
+    env_->GetCurrentTime(&_current_time);  // ignore error
     const uint64_t current_time = static_cast<uint64_t>(_current_time);
 
     {

db/flush_job.cc

@@ -299,11 +299,8 @@ Status FlushJob::WriteLevel0Table() {
       EnvOptions optimized_env_options =
           db_options_.env->OptimizeForCompactionTableWrite(env_options_, db_options_);
 
-      int64_t _current_time;
-      auto status = db_options_.env->GetCurrentTime(&_current_time);
-      if (!status.ok()) {
-        _current_time = 0;
-      }
+      int64_t _current_time = 0;
+      db_options_.env->GetCurrentTime(&_current_time);  // ignore error
       const uint64_t current_time = static_cast<uint64_t>(_current_time);
 
       s = BuildTable(

db/repair.cc

@@ -383,11 +383,8 @@ class Repairer {
       EnvOptions optimized_env_options =
           env_->OptimizeForCompactionTableWrite(env_options_, immutable_db_options_);
 
-      int64_t _current_time;
-      status = env_->GetCurrentTime(&_current_time);
-      if (!status.ok()) {
-        _current_time = 0;
-      }
+      int64_t _current_time = 0;
+      status = env_->GetCurrentTime(&_current_time);  // ignore error
       const uint64_t current_time = static_cast<uint64_t>(_current_time);
 
       status = BuildTable(

env/mock_env.cc

@@ -148,7 +148,7 @@ class MemFile {
 
  private:
   uint64_t Now() {
-    int64_t unix_time;
+    int64_t unix_time = 0;
     auto s = env_->GetCurrentTime(&unix_time);
     assert(s.ok());
     return static_cast<uint64_t>(unix_time);
@@ -734,7 +734,9 @@ Status MockEnv::GetTestDirectory(std::string* path) {
 
 Status MockEnv::GetCurrentTime(int64_t* unix_time) {
   auto s = EnvWrapper::GetCurrentTime(unix_time);
-  *unix_time += fake_sleep_micros_.load() / (1000 * 1000);
+  if (s.ok()) {
+    *unix_time += fake_sleep_micros_.load() / (1000 * 1000);
+  }
   return s;
 }
 

include/rocksdb/env.h

@@ -353,6 +353,7 @@ class Env {
   virtual Status GetHostName(char* name, uint64_t len) = 0;
 
   // Get the number of seconds since the Epoch, 1970-01-01 00:00:00 (UTC).
+  // Only overwrites *unix_time on success.
   virtual Status GetCurrentTime(int64_t* unix_time) = 0;
 
   // Get full directory name for this db.

tools/dump/db_dump_tool.cc

@@ -27,7 +27,7 @@ bool DbDumpTool::Run(const DumpOptions& dump_options,
   rocksdb::Status status;
   std::unique_ptr<rocksdb::WritableFile> dumpfile;
   char hostname[1024];
-  int64_t timesec;
+  int64_t timesec = 0;
   std::string abspath;
   char json[4096];
 

utilities/date_tiered/date_tiered_test.cc

@@ -37,7 +37,7 @@ class SpecialTimeEnv : public EnvWrapper {
   }
 
  private:
-  int64_t current_time_;
+  int64_t current_time_ = 0;
 };
 
 class DateTieredTest : public testing::Test {

utilities/ttl/ttl_test.cc

@@ -36,7 +36,7 @@ class SpecialTimeEnv : public EnvWrapper {
   }
 
  private:
-  int64_t current_time_;
+  int64_t current_time_ = 0;
 };
 
 class TtlTest : public testing::Test {