allow --check --valgrind to pass again

src/common/buffer.cc

@@ -75,11 +75,7 @@ struct BufferData {
    */
   uint8_t m_data[1];
 };
-class BufferDataList : public std::vector<struct BufferData*>
-{
-public:
-  ~BufferDataList ();
-};
+typedef std::vector<struct BufferData*> BufferDataList;
 
 static struct BufferData *BufferAllocate (uint32_t reqSize);
 
@@ -91,39 +87,69 @@ static void BufferDeallocate (struct BufferData *data);
 namespace ns3 {
 
 #ifdef BUFFER_HEURISTICS
+/* The following macros are pretty evil but they are needed to allow us to
+ * keep track of 3 possible states for the g_freeList variable:
+ *  - uninitialized means that no one has created a buffer yet
+ *    so no one has created the associated free list (it is created
+ *    on-demand when the first buffer is created)
+ *  - initialized means that the free list exists and is valid
+ *  - destroyed means that the static destructors of this compilation unit
+ *    have run so, the free list has been cleared from its content
+ * The key is that in destroyed state, we are careful not re-create it
+ * which is a typical weakness of lazy evaluation schemes which use 
+ * '0' as a special value to indicate both un-initialized and destroyed.
+ * Note that it is important to use '0' as the marker for un-initialized state
+ * because the variable holding this state information is initialized to zero
+ * which the compiler assigns to zero-memory which is initialized to _zero_
+ * before the constructors run so this ensures perfect handling of crazy 
+ * constructor orderings.
+ */
+#define MAGIC_DESTROYED (~(long) 0)
+#define IS_UNINITIALIZED(x) (x == (BufferDataList*)0)
+#define IS_DESTROYED(x) (x == (BufferDataList*)MAGIC_DESTROYED)
+#define IS_INITIALIZED(x) (!IS_UNINITIALIZED(x) && !IS_DESTROYED(x))
+#define DESTROYED ((BufferDataList*)MAGIC_DESTROYED)
+#define UNINITIALIZED ((BufferDataList*)0)
 static uint32_t g_recommendedStart = 0;
 static uint64_t g_nAddNoRealloc = 0;
 static uint64_t g_nAddRealloc = 0;
-static BufferDataList  g_freeList;
+static BufferDataList *g_freeList = 0;
 static uint32_t g_maxSize = 0;
 static uint64_t g_nAllocs = 0;
 static uint64_t g_nCreates = 0;
 #endif /* BUFFER_HEURISTICS */
 
-BufferDataList::~BufferDataList ()
-{
+static struct LocalStaticDestructor {
+  LocalStaticDestructor(void)
+  {
 #ifdef PRINT_STATS
 #ifdef BUFFER_HEURISTICS
-  double efficiency;
-  efficiency = g_nAllocs;
-  efficiency /= g_nCreates;
-  std::cout <<"buffer free list efficiency="<<efficiency<<" (lower is better)" << std::endl;
-  std::cout <<"buffer free list max size="<<g_maxSize<<std::endl;
-  std::cout <<"buffer free list recommended start="<<g_recommendedStart<<std::endl;
-  double addEfficiency;
-  addEfficiency = g_nAddRealloc;
-  addEfficiency /= g_nAddNoRealloc;
-  std::cout <<"buffer add efficiency=" << addEfficiency << " (lower is better)"<<std::endl;
-  //std::cout <<"n add reallocs="<< g_nAddRealloc << std::endl;
-  //std::cout <<"n add no reallocs="<< g_nAddNoRealloc << std::endl;
+    double efficiency;
+    efficiency = g_nAllocs;
+    efficiency /= g_nCreates;
+    std::cout <<"buffer free list efficiency="<<efficiency<<" (lower is better)" << std::endl;
+    std::cout <<"buffer free list max size="<<g_maxSize<<std::endl;
+    std::cout <<"buffer free list recommended start="<<g_recommendedStart<<std::endl;
+    double addEfficiency;
+    addEfficiency = g_nAddRealloc;
+    addEfficiency /= g_nAddNoRealloc;
+    std::cout <<"buffer add efficiency=" << addEfficiency << " (lower is better)"<<std::endl;
+    //std::cout <<"n add reallocs="<< g_nAddRealloc << std::endl;
+    //std::cout <<"n add no reallocs="<< g_nAddNoRealloc << std::endl;
 #endif /* BUFFER_HEURISTICS */
 #endif /* PRINT_STATS */
-  for (BufferDataList::iterator i = begin ();
-       i != end (); i++)
-    {
-      BufferDeallocate (*i);
-    }
-}
+    if (IS_INITIALIZED(g_freeList))
+      {
+        for (BufferDataList::iterator i = g_freeList->begin ();
+             i != g_freeList->end (); i++)
+          {
+            BufferDeallocate (*i);
+          }
+        delete g_freeList;
+        g_freeList = DESTROYED;
+      }
+  }
+} g_localStaticDestructor;
 
 struct BufferData *
 BufferAllocate (uint32_t reqSize)
@@ -153,16 +179,19 @@ void
 Buffer::Recycle (struct BufferData *data)
 {
   NS_ASSERT (data->m_count == 0);
+  NS_ASSERT (!IS_UNINITIALIZED(g_freeList));
   g_maxSize = std::max (g_maxSize, data->m_size);
   /* feed into free list */
   if (data->m_size < g_maxSize ||
-      g_freeList.size () > 1000)
+      IS_DESTROYED(g_freeList) ||
+      g_freeList->size () > 1000)
     {
       BufferDeallocate (data);
     }
   else
     {
-      g_freeList.push_back (data);
+      NS_ASSERT (IS_INITIALIZED(g_freeList));
+      g_freeList->push_back (data);
     }
 }
 
@@ -171,16 +200,23 @@ Buffer::Create (uint32_t dataSize)
 {
   /* try to find a buffer correctly sized. */
   g_nCreates++;
-  while (!g_freeList.empty ()) 
+  if (IS_UNINITIALIZED(g_freeList))
     {
-      struct BufferData *data = g_freeList.back ();
-      g_freeList.pop_back ();
-      if (data->m_size >= dataSize) 
+      g_freeList = new BufferDataList ();
+    }
+  else if (IS_INITIALIZED(g_freeList))
+    {
+      while (!g_freeList->empty ()) 
         {
-          data->m_count = 1;
-          return data;
+          struct BufferData *data = g_freeList->back ();
+          g_freeList->pop_back ();
+          if (data->m_size >= dataSize) 
+            {
+              data->m_count = 1;
+              return data;
+            }
+          BufferDeallocate (data);
         }
-      BufferDeallocate (data);
     }
   g_nAllocs++;
   struct BufferData *data = BufferAllocate (dataSize);