From 41cb922b34fd231bfb0e78af92168375b57b308f Mon Sep 17 00:00:00 2001
From: Abhishek Kona <abhishekk@fb.com>
Date: Mon, 29 Apr 2013 13:19:24 -0700
Subject: [PATCH] Allocate the LogReporter from heap. Summary:

Summary:
The current code has a bug that take address of stack allocated LogReporter.
It is causing SIGSEGV because the stack address is no longer valid when referenced.

Test Plan: Tested on prod.

Reviewers: haobo, dhruba, heyongqiang

Reviewed By: heyongqiang

Differential Revision: https://reviews.facebook.net/D10557
---
 db/transaction_log_iterator_impl.cc | 18 +++++-------------
 db/transaction_log_iterator_impl.h  |  6 ++----
 2 files changed, 7 insertions(+), 17 deletions(-)

diff --git a/db/transaction_log_iterator_impl.cc b/db/transaction_log_iterator_impl.cc
index 1b0f25b2e..0b1f47d72 100644
--- a/db/transaction_log_iterator_impl.cc
+++ b/db/transaction_log_iterator_impl.cc
@@ -22,15 +22,9 @@ TransactionLogIteratorImpl::TransactionLogIteratorImpl(
   lastFlushedSequence_(lastFlushedSequence) {
   assert(files_.get() != nullptr);
   assert(lastFlushedSequence_);
-}
 
-LogReporter
-TransactionLogIteratorImpl::NewLogReporter(const uint64_t logNumber) {
-  LogReporter reporter;
-  reporter.env = options_->env;
-  reporter.info_log = options_->info_log.get();
-  reporter.log_number = logNumber;
-  return reporter;
+  reporter_.env = options_->env;
+  reporter_.info_log = options_->info_log.get();
 }
 
 Status TransactionLogIteratorImpl::OpenLogFile(
@@ -74,7 +68,6 @@ bool TransactionLogIteratorImpl::Valid() {
 
 void TransactionLogIteratorImpl::Next() {
   LogFile currentLogFile = files_.get()->at(currentFileIndex_);
-  LogReporter reporter = NewLogReporter(currentLogFile.logNumber);
 
 //  First seek to the given seqNo. in the current file.
   std::string scratch;
@@ -95,7 +88,7 @@ void TransactionLogIteratorImpl::Next() {
     }
     while (currentLogReader_->ReadRecord(&record, &scratch)) {
       if (record.size() < 12) {
-        reporter.Corruption(
+        reporter_.Corruption(
           record.size(), Status::Corruption("log record too small"));
         continue;
       }
@@ -122,7 +115,7 @@ void TransactionLogIteratorImpl::Next() {
       }
       while (currentLogReader_->ReadRecord(&record, &scratch)) {
         if (record.size() < 12) {
-          reporter.Corruption(
+          reporter_.Corruption(
             record.size(), Status::Corruption("log record too small"));
           continue;
         } else {
@@ -165,7 +158,6 @@ void TransactionLogIteratorImpl::UpdateCurrentWriteBatch(const Slice& record) {
 }
 
 Status TransactionLogIteratorImpl::OpenLogReader(const LogFile& logFile) {
-  LogReporter reporter = NewLogReporter(logFile.logNumber);
   unique_ptr<SequentialFile> file;
   Status status = OpenLogFile(logFile, &file);
   if (!status.ok()) {
@@ -173,7 +165,7 @@ Status TransactionLogIteratorImpl::OpenLogReader(const LogFile& logFile) {
   }
   assert(file);
   currentLogReader_.reset(
-    new log::Reader(std::move(file), &reporter, true, 0)
+    new log::Reader(std::move(file), &reporter_, true, 0)
   );
   return Status::OK();
 }
diff --git a/db/transaction_log_iterator_impl.h b/db/transaction_log_iterator_impl.h
index f682fabc7..90fd1fcf0 100644
--- a/db/transaction_log_iterator_impl.h
+++ b/db/transaction_log_iterator_impl.h
@@ -17,10 +17,8 @@ namespace leveldb {
 struct LogReporter : public log::Reader::Reporter {
   Env* env;
   Logger* info_log;
-  uint64_t log_number;
   virtual void Corruption(size_t bytes, const Status& s) {
-    Log(info_log, "%ld: dropping %d bytes; %s",
-        log_number, static_cast<int>(bytes), s.ToString().c_str());
+    Log(info_log, "dropping %zu bytes; %s", bytes, s.ToString().c_str());
   }
 };
 
@@ -54,7 +52,7 @@ class TransactionLogIteratorImpl : public TransactionLogIterator {
   std::unique_ptr<WriteBatch> currentBatch_;
   unique_ptr<log::Reader> currentLogReader_;
   Status OpenLogFile(const LogFile& logFile, unique_ptr<SequentialFile>* file);
-  LogReporter NewLogReporter(uint64_t logNumber);
+  LogReporter reporter_;
   SequenceNumber const * const lastFlushedSequence_;
   // represents the sequence number being read currently.
   SequenceNumber currentSequence_;