Initial GetSample implementation.

include/v8.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /** \mainpage V8 API Reference Guide
  *
  * V8 is Google's open source JavaScript engine.
  *
  * This set of documents provides reference material generated from the
  * V8 header file, include/v8.h.
@@ skipping 1304 matching lines @@
 
   /**
    * Returns whether or not the associated function is called as a
    * constructor via "new".
    */
   bool IsConstructor() const;
 };
 
 
 /**
+ * Isolate::GetSample collects the current JS execution state as a sample.
+ * A collected sample contains program counter values.
+ *
+ * Example: Printing out the stack frames' addresses, from top to bottom.
+ *
+ * Isolate* isolate = Isolate::Current();
+ * Sample sample;
+ * isolate->GetSample(&sample);
+ * const void* const* i;
+ * for (i = sample.begin(); i != sample.end(); ++i) {
+ *   printf("%p\n", *i);
+ * }
+ */
+class V8_EXPORT Sample {
+ public:
+  enum { kMaxSize = 255u };
+
+  Sample() : size_(0) {}
+  template <class InputIterator>
+  Sample(InputIterator first, InputIterator last)
+      : size_(0) {
+    for (; first != last && size_ < kMaxSize; ++first) data_[size_++] = *first;
+  }
+
+  typedef const void* const* const_iterator;
+  const_iterator begin() const { return &data_[0]; }
+  const_iterator end() const { return &data_[size_]; }
+  size_t size() const { return size_; }
+
+ private:
+  const void* data_[kMaxSize];
+  size_t size_;
+};
+
+/**
  * A JSON Parser.
  */
 class V8_EXPORT JSON {
  public:
   /**
    * Tries to parse the string |json_string| and returns it as value if
    * successful.
    *
    * \param json_string The string to parse.
    * \return The corresponding value if successfully parsed.
@@ skipping 2977 matching lines @@
    * are in the range of 0 - GetNumberOfDataSlots() - 1.
    */
   V8_INLINE static uint32_t GetNumberOfDataSlots();
 
   /**
    * Get statistics about the heap memory usage.
    */
   void GetHeapStatistics(HeapStatistics* heap_statistics);
 
   /**
+   * Get a sample from the isolate.
+   */
+  void GetSample(Sample* sample);

[yurys, 2014/09/09 14:35:20]

This is not what the document proposed. The idea was to expose an API for
collecting current v8 stack trace on a paused thread. It is the embedder who
should be responsible for pausing the thread (using SIGPROF or SuspendThread)
and calling GetSample. Introducing such API would allow us to move profiler
implementation out of V8 into e.g. Blink. With GetSample introduced in this CL
we will have to keep all the platform-specific profiler code in v8.

[jochen (gone - plz use gerrit), 2014/09/10 07:39:20]

Agreed.

We'll soon delete threads from v8 and instead solely rely on embedder threads,
then this won't work anymore anyways

[gholap, 2014/09/17 02:35:06]

Acknowledged.

+
+  /**
    * Adjusts the amount of registered external memory. Used to give V8 an
    * indication of the amount of externally allocated memory that is kept alive
    * by JavaScript objects. V8 uses this to decide when to perform global
    * garbage collections. Registering externally allocated memory will trigger
    * global garbage collections more often than it would otherwise in an attempt
    * to garbage collect the JavaScript objects that keep the externally
    * allocated memory alive.
    *
    * \param change_in_bytes the change in externally allocated memory that is
    *   kept alive by JavaScript objects.
@@ skipping 2492 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // V8_H_