Annotate ThreadData::PushToHeadOfList for MemorySanitizer.

base/tracked_objects.cc

Index: base/tracked_objects.cc
diff --git a/base/tracked_objects.cc b/base/tracked_objects.cc
index b3bc975374275e56ee40fc6959fea3d6b29fc8c7..209ec7dc904af14fd753baace1dd9a9b74922db7 100644
--- a/base/tracked_objects.cc
+++ b/base/tracked_objects.cc
@@ -7,6 +7,7 @@
 #include <math.h>
 #include <stdlib.h>
 
+#include "base/compiler_specific.h"
 #include "base/format_macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/process_util.h"
@@ -258,6 +259,7 @@ void ThreadData::PushToHeadOfList() {
   // Toss in a hint of randomness (atop the uniniitalized value).
   (void)VALGRIND_MAKE_MEM_DEFINED_IF_ADDRESSABLE(&random_number_,
                                                  sizeof(random_number_));
+  __msan_unpoison(&random_number_, sizeof(random_number_));

[Alexander Potapenko, 2013/03/20 11:19:43]

As I've said before, it isn't obvious that __msan_unpoison() is a no-op if
MEMORY_SANITIZER is not defined.

I suggest to:
 - remove the leading underscores, since they denote that the identifier is
reserved by the compiler (this is ok under '#ifdef MEMORY_SANITIZER', but not in
the regular mode)
 - use uppercase only (to show this is a macro, not a function call)

   random_number_ += static_cast<int32>(this - static_cast<ThreadData*>(0));
   random_number_ ^= (Now() - TrackedTime()).InMilliseconds();