Experiment for updating the tcmalloc chromium branch to r144 (gperftools 2.0).

third_party/tcmalloc/chromium/src/base/basictypes.h

Index: third_party/tcmalloc/chromium/src/base/basictypes.h
diff --git a/third_party/tcmalloc/chromium/src/base/basictypes.h b/third_party/tcmalloc/chromium/src/base/basictypes.h
index 0f21fcae9e78ba178893619371006f18a62fe675..75b7b5ae777ae06b81ad63aa3912df8b58368aab 100644
--- a/third_party/tcmalloc/chromium/src/base/basictypes.h
+++ b/third_party/tcmalloc/chromium/src/base/basictypes.h
@@ -31,6 +31,7 @@
 #define _BASICTYPES_H_
 
 #include <config.h>
+#include <string.h>       // for memcpy()
 #ifdef HAVE_INTTYPES_H
 #include <inttypes.h>     // gets us PRId64, etc
 #endif
@@ -193,6 +194,28 @@ struct CompileAssert {
    (reinterpret_cast<char*>(&reinterpret_cast<strct*>(16)->field) -     \
     reinterpret_cast<char*>(16))
 
+// bit_cast<Dest,Source> implements the equivalent of
+// "*reinterpret_cast<Dest*>(&source)".
+//
+// The reinterpret_cast method would produce undefined behavior
+// according to ISO C++ specification section 3.10 -15 -.
+// bit_cast<> calls memcpy() which is blessed by the standard,
+// especially by the example in section 3.9.
+//
+// Fortunately memcpy() is very fast.  In optimized mode, with a
+// constant size, gcc 2.95.3, gcc 4.0.1, and msvc 7.1 produce inline
+// code with the minimal amount of data movement.  On a 32-bit system,
+// memcpy(d,s,4) compiles to one load and one store, and memcpy(d,s,8)
+// compiles to two loads and two stores.
+
+template <class Dest, class Source>
+inline Dest bit_cast(const Source& source) {
+  COMPILE_ASSERT(sizeof(Dest) == sizeof(Source), bitcasting_unequal_sizes);
+  Dest dest;
+  memcpy(&dest, &source, sizeof(dest));
+  return dest;
+}
+
 #ifdef HAVE___ATTRIBUTE__
 # define ATTRIBUTE_WEAK      __attribute__((weak))
 # define ATTRIBUTE_NOINLINE  __attribute__((noinline))
@@ -309,8 +332,7 @@ class AssignAttributeStartEnd {
 #endif  // HAVE___ATTRIBUTE__ and __ELF__ or __MACH__
 
 #if defined(HAVE___ATTRIBUTE__) && (defined(__i386__) || defined(__x86_64__))
-# define CACHELINE_SIZE 64
-# define CACHELINE_ALIGNED __attribute__((aligned(CACHELINE_SIZE)))
+# define CACHELINE_ALIGNED __attribute__((aligned(64)))
 #else
 # define CACHELINE_ALIGNED
 #endif  // defined(HAVE___ATTRIBUTE__) && (__i386__ || __x86_64__)