From 0adaab0ad9ad5df36da89413f3bed03a9f7cfa4b Mon Sep 17 00:00:00 2001
From: Mathieu Lacage <mathieu.lacage@sophia.inria.fr>
Date: Tue, 6 Jul 2010 09:07:15 +0200
Subject: [PATCH] plug leak

---
 src/core/fatal-impl.cc | 38 +++++++++++++++++++++++++++++++++++---
 1 file changed, 35 insertions(+), 3 deletions(-)

diff --git a/src/core/fatal-impl.cc b/src/core/fatal-impl.cc
index 0d16bb692..9ee654a57 100644
--- a/src/core/fatal-impl.cc
+++ b/src/core/fatal-impl.cc
@@ -30,6 +30,19 @@
 namespace ns3 {
 namespace FatalImpl {
 
+/**
+ * Note on implementation: the singleton pattern we use here is tricky because
+ * it has to deal with:
+ *   - make sure that whoever calls Register (potentially before main enters and 
+ *     before any constructor run in this file) succeeds
+ *   - make sure that whoever calls Unregister (potentially before FlushStream runs
+ *     but also after it runs) succeeds
+ *   - make sure that the memory allocated with new is deallocated with delete before
+ *     the program exits so that valgrind reports no leaks
+ *
+ * This is why we go through all the painful hoops below.
+ */
+
 /* File-scope */
 namespace {
   std::list<std::ostream*> **PeekStreamList (void)
@@ -66,7 +79,17 @@ RegisterStream (std::ostream* stream)
 void
 UnregisterStream (std::ostream* stream)
 {
-  GetStreamList ()->remove (stream);
+  std::list<std::ostream*> **pl = PeekStreamList ();
+  if (*pl == 0)
+    {
+      return;
+    }
+  (*pl)->remove (stream);
+  if ((*pl)->empty ())
+    {
+      delete *pl;
+      *pl = 0;
+    }
 }
 
 
@@ -83,16 +106,22 @@ namespace {
 void 
 FlushStreams (void)
 {
-  struct sigaction hdl;
+  std::list<std::ostream*> **pl = PeekStreamList ();
+  if (pl == 0)
+    {
+      return;
+    }
+
 
   /* Override default SIGSEGV handler - will flush subsequent
    * streams even if one of the stream pointers is bad.
    * The SIGSEGV override should only be active for the
    * duration of this function. */
+  struct sigaction hdl;
   hdl.sa_handler=sigHandler;
   sigaction (SIGSEGV, &hdl, 0);
 
-  std::list<std::ostream*> *l = GetStreamList ();
+  std::list<std::ostream*> *l = *pl;
 
   /* Need to do it this way in case any of the ostream* causes SIGSEGV */
   while (!l->empty ())
@@ -113,6 +142,9 @@ FlushStreams (void)
   std::cout.flush ();
   std::cerr.flush ();
   std::clog.flush ();
+
+  delete l;
+  *pl = 0;
 }
 
 } //FatalImpl