make debug mode ~20% faster on linux

base/threading/platform_thread.h

Index: base/threading/platform_thread.h
diff --git a/base/threading/platform_thread.h b/base/threading/platform_thread.h
index f2f3b260586cdcf67a75fae4b0a3e0119ece61f6..a983d70381ec787339348b1ac997b27a45885900 100644
--- a/base/threading/platform_thread.h
+++ b/base/threading/platform_thread.h
@@ -23,12 +23,42 @@
 
 namespace base {
 
+// Used for logging. Always an integer value.
 #if defined(OS_WIN)
 typedef DWORD PlatformThreadId;
 #elif defined(OS_POSIX)
 typedef pid_t PlatformThreadId;
 #endif
 
+// Used for thread checking and debugging.
+// Meant to be as fast as possible.

[Mark Mentovai, 2014/05/23 17:55:16]

Your comment should say something about the uniqueness guarantees: for example,
will the same thread always have the same PlatformThreadRef? Can two
PlatformThreadRefs identify the same thread? Can a PlatformThreadRef that once
referred to a now-dead thread subsequently refer to a different thread? It’s OK
for some of these to be unspecified, but you need to say more than what you’ve
said in this comment.

[hubbe, 2014/05/23 19:31:14]

Better?

+class PlatformThreadRef {
+ public:
+#if defined(OS_WIN)
+  typedef DWORD RefType;
+#elif defined(OS_POSIX)
+  typedef pthread_t RefType;
+#endif
+  PlatformThreadRef()
+      : id_(0) {
+  }
+
+  explicit PlatformThreadRef(RefType id)
+      : id_(id) {
+  }
+
+  bool operator==(PlatformThreadRef other) const {
+    return id_ == other.id_;
+  }
+
+  bool is_null() const {
+    return id_ == 0;
+  }
+ private:
+  RefType id_;
+};
+
+// Used to operate on threads.
 class PlatformThreadHandle {
  public:
 #if defined(OS_WIN)
@@ -101,6 +131,10 @@ class BASE_EXPORT PlatformThread {
   // Gets the current thread id, which may be useful for logging purposes.
   static PlatformThreadId CurrentId();
 
+  // Gets the current thread reference, which can be used to check if
+  // we're on the right thread quickly.
+  static PlatformThreadRef CurrentRef();
+
   // Get the current handle.
   static PlatformThreadHandle CurrentHandle();