diff --git a/Makefile b/Makefile
index 18386f28b..8385d4481 100644
--- a/Makefile
+++ b/Makefile
@@ -8,9 +8,9 @@ CC = g++
 # Uncomment exactly one of the lines labelled (A), (B), and (C) below
 # to switch between compilation modes.
 
-OPT = -O2 -DNDEBUG       # (A) Production use (optimized mode)
-# OPT = -g2              # (B) Debug mode, w/ full line-level debugging symbols
-# OPT = -O2 -g2 -DNDEBUG # (C) Profiling mode: opt, but w/debugging symbols
+OPT ?= -O2 -DNDEBUG       # (A) Production use (optimized mode)
+# OPT ?= -g2              # (B) Debug mode, w/ full line-level debugging symbols
+# OPT ?= -O2 -g2 -DNDEBUG # (C) Profiling mode: opt, but w/debugging symbols
 #-----------------------------------------------
 
 # detect what platform we're building on
@@ -38,7 +38,7 @@ endif
 
 CFLAGS = -c -I. -I./include $(PORT_CFLAGS) $(PLATFORM_CFLAGS) $(OPT) $(SNAPPY_CFLAGS)
 
-LDFLAGS=$(PLATFORM_LDFLAGS) $(SNAPPY_LDFLAGS) $(GOOGLE_PERFTOOLS_LDFLAGS)
+LDFLAGS += $(PLATFORM_LDFLAGS) $(SNAPPY_LDFLAGS) $(GOOGLE_PERFTOOLS_LDFLAGS)
 
 LIBOBJECTS = \
 	./db/builder.o \
diff --git a/db/db_test.cc b/db/db_test.cc
index f1cb94921..5dc3b026d 100644
--- a/db/db_test.cc
+++ b/db/db_test.cc
@@ -1146,26 +1146,50 @@ TEST(DBTest, CustomComparator) {
    public:
     virtual const char* Name() const { return "test.NumberComparator"; }
     virtual int Compare(const Slice& a, const Slice& b) const {
-      return (strtol(a.ToString().c_str(), NULL, 0) -
-              strtol(b.ToString().c_str(), NULL, 0));
+      return ToNumber(a) - ToNumber(b);
+    }
+    virtual void FindShortestSeparator(std::string* s, const Slice& l) const {
+      ToNumber(*s);     // Check format
+      ToNumber(l);      // Check format
+    }
+    virtual void FindShortSuccessor(std::string* key) const {
+      ToNumber(*key);   // Check format
+    }
+   private:
+    static int ToNumber(const Slice& x) {
+      // Check that there are no extra characters.
+      ASSERT_TRUE(x.size() >= 2 && x[0] == '[' && x[x.size()-1] == ']')
+          << EscapeString(x);
+      int val;
+      char ignored;
+      ASSERT_TRUE(sscanf(x.ToString().c_str(), "[%i]%c", &val, &ignored) == 1)
+          << EscapeString(x);
+      return val;
     }
-    virtual void FindShortestSeparator(std::string* s, const Slice& l) const {}
-    virtual void FindShortSuccessor(std::string* key) const {}
   };
   NumberComparator cmp;
   Options new_options;
   new_options.create_if_missing = true;
   new_options.comparator = &cmp;
+  new_options.write_buffer_size = 1000;  // Compact more often
   DestroyAndReopen(&new_options);
-  ASSERT_OK(Put("10", "ten"));
-  ASSERT_OK(Put("0x14", "twenty"));
+  ASSERT_OK(Put("[10]", "ten"));
+  ASSERT_OK(Put("[0x14]", "twenty"));
   for (int i = 0; i < 2; i++) {
-    ASSERT_EQ("ten", Get("10"));
-    ASSERT_EQ("ten", Get("0xa"));
-    ASSERT_EQ("twenty", Get("20"));
-    ASSERT_EQ("twenty", Get("0x14"));
-    Compact("0", "9999");
-    fprintf(stderr, "ss\n%s\n", DumpSSTableList().c_str());
+    ASSERT_EQ("ten", Get("[10]"));
+    ASSERT_EQ("ten", Get("[0xa]"));
+    ASSERT_EQ("twenty", Get("[20]"));
+    ASSERT_EQ("twenty", Get("[0x14]"));
+    Compact("[0]", "[9999]");
+  }
+
+  for (int run = 0; run < 2; run++) {
+    for (int i = 0; i < 1000; i++) {
+      char buf[100];
+      snprintf(buf, sizeof(buf), "[%d]", i*10);
+      ASSERT_OK(Put(buf, buf));
+    }
+    Compact("[0]", "[1000000]");
   }
 }
 
diff --git a/db/dbformat.cc b/db/dbformat.cc
index 4594a5700..9168f99df 100644
--- a/db/dbformat.cc
+++ b/db/dbformat.cc
@@ -73,9 +73,10 @@ void InternalKeyComparator::FindShortestSeparator(
   Slice user_limit = ExtractUserKey(limit);
   std::string tmp(user_start.data(), user_start.size());
   user_comparator_->FindShortestSeparator(&tmp, user_limit);
-  if (user_comparator_->Compare(*start, tmp) < 0) {
-    // User key has become larger.  Tack on the earliest possible
-    // number to the shortened user key.
+  if (tmp.size() < user_start.size() &&
+      user_comparator_->Compare(user_start, tmp) < 0) {
+    // User key has become shorter physically, but larger logically.
+    // Tack on the earliest possible number to the shortened user key.
     PutFixed64(&tmp, PackSequenceAndType(kMaxSequenceNumber,kValueTypeForSeek));
     assert(this->Compare(*start, tmp) < 0);
     assert(this->Compare(tmp, limit) < 0);
@@ -87,9 +88,10 @@ void InternalKeyComparator::FindShortSuccessor(std::string* key) const {
   Slice user_key = ExtractUserKey(*key);
   std::string tmp(user_key.data(), user_key.size());
   user_comparator_->FindShortSuccessor(&tmp);
-  if (user_comparator_->Compare(user_key, tmp) < 0) {
-    // User key has become larger.  Tack on the earliest possible
-    // number to the shortened user key.
+  if (tmp.size() < user_key.size() &&
+      user_comparator_->Compare(user_key, tmp) < 0) {
+    // User key has become shorter physically, but larger logically.
+    // Tack on the earliest possible number to the shortened user key.
     PutFixed64(&tmp, PackSequenceAndType(kMaxSequenceNumber,kValueTypeForSeek));
     assert(this->Compare(*key, tmp) < 0);
     key->swap(tmp);
diff --git a/util/comparator.cc b/util/comparator.cc
index cfb49ceed..eed9d2fcd 100644
--- a/util/comparator.cc
+++ b/util/comparator.cc
@@ -64,10 +64,13 @@ class BytewiseComparatorImpl : public Comparator {
   }
 };
 }  // namespace
-static const BytewiseComparatorImpl bytewise;
+
+// Intentionally not destroyed to prevent destructor racing
+// with background threads.
+static const Comparator* bytewise = new BytewiseComparatorImpl;
 
 const Comparator* BytewiseComparator() {
-  return &bytewise;
+  return bytewise;
 }
 
 }  // namespace leveldb