chromium之tracked

//------------------------------------------------------------------------------

// Tracked is the base class for all tracked objects.  During construction, it

// registers the fact that an instance was created, and at destruction time, it

// records that event.  The instance may be tagged with a name, which is refered

// to as its Location.  The Location is a file and line number, most

// typically indicated where the object was constructed.  In some cases, as the

// object's significance is refined (for example, a Task object is augmented to

// do additonal things), its Location may be redefined to that later location.

// Tracking includes (for each instance) recording the birth thread, death

// thread, and duration of life (from construction to destruction).  All this

// data is accumulated and filtered for review at about:objects.

信息跟踪收集，用于统计分析的工具

---

下面的代码是不是很熟悉，FROM_HERE

message_loop->PostTask(FROM_HERE,...)

#define FROM_HERE tracked_objects::Location(__FUNCTION__, __FILE__, __LINE__)

构造函数如下：

class Location {

 public:

  // Constructor should be called with a long-lived char*, such as __FILE__.

  // It assumes the provided value will persist as a global constant, and it

  // will not make a copy of it.

  Location(const char* function_name, const char* file_name, int line_number)

      : function_name_(function_name),

        file_name_(file_name),

        line_number_(line_number) { }

}

记录了函数名，文件名，行号

不过，只有在调试模式，才会有比较详细的统计信息

#ifndef NDEBUG

#ifndef TRACK_ALL_TASK_OBJECTS

#define TRACK_ALL_TASK_OBJECTS

#endif   // TRACK_ALL_TASK_OBJECTS

#endif  // NDEBUG

调试模式下，多了一个没见过的ThreadData，可以分析分析chromium之tracked_objects

Tracked::Tracked() : tracked_births_(NULL), tracked_birth_time_(Time::Now()) {

  if (!ThreadData::IsActive())

    return;

  SetBirthPlace(Location("NoFunctionName", "NeedToSetBirthPlace", -));

}