Type profiler by intercepting 'new' and 'delete' expressions.

base/allocator/allocated_type_profiler_ignore.cc

Index: base/allocator/allocated_type_profiler_ignore.cc
diff --git a/base/allocator/allocated_type_profiler_ignore.cc b/base/allocator/allocated_type_profiler_ignore.cc
new file mode 100644
index 0000000000000000000000000000000000000000..9da67d1c56331657fce067e710014dc9d4b30083
--- /dev/null
+++ b/base/allocator/allocated_type_profiler_ignore.cc
@@ -0,0 +1,17 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "allocated_type_profiler.h"
+
+void* __op_new_intercept__(void* ptr,
+                           size_t size,
+                           const std::type_info& type) {
+  return ptr;
+}
+
+void* __op_delete_intercept__(void* ptr,
+                              size_t size,
+                              const std::type_info& type) {
+  return ptr;
+}

[Ryan Sleevi, 2012/08/10 04:16:09]

Seems like you shouldn't even be wrapping these functions if you're not going to
do anything.

I'm not even sure if Clang/GCC will be able to optimize these out - even though
they're *effectively* no-op, without Whole Program optimization, it won't be
able to no-op the calls out at all the callsites.

[Dai Mikurube (NOT FULLTIME), 2012/08/10 07:30:03]

These no-op interceptors are used for non-tcmalloc binaries.  It is because the
storage for allocated types depends on tcmalloc's lock.  We need to switch it by
target binaries: e.g. turn off for mksnapshot and turn on for chrome.

Almost all .cc files should have prototype declarations of these functions when
this feature is enabled.  A .cc file may be used for two kinds of binaries: e.g.
mksnapshot and chrome.  (I am not sure, but I cannot guarantee... or, can we
assume that?)

It is the reason why I switch them at linking phase by preparing multiple build
targets: allocated_type_profiler_tcmalloc and allocated_type_profiler_ignore.

I agree with that they might not be "effective" no-ops.  But, this feature is
enabled only for profiling, and these _ignore interceptors are used only for
some commands: e.g. mksnapshot and protoc.  I think it is acceptable and
reasonable.

[Ryan Sleevi, 2012/08/10 09:38:50]

In that case, wouldn't it just be better not to interpose at all for non-audited
targets? (see GYP comments)