[debugger] implement inspector-facing API for code coverage.

src/debug/debug-coverage.cc

 // Copyright 2017 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.
 
 #include "src/debug/debug-coverage.h"
 
 #include "src/base/hashmap.h"
 #include "src/deoptimizer.h"
 #include "src/isolate.h"
 #include "src/objects-inl.h"
@@ skipping 40 matching lines @@
 }
 
 bool CompareSharedFunctionInfo(SharedFunctionInfo* a, SharedFunctionInfo* b) {
   int a_start = StartPosition(a);
   int b_start = StartPosition(b);
   if (a_start == b_start) return a->end_position() > b->end_position();
   return a_start < b_start;
 }
 }  // anonymous namespace
 
-std::vector<Coverage::ScriptData> Coverage::Collect(Isolate* isolate) {
+CoverageScript::CoverageScript(Isolate* isolate, Handle<Script> s,
+                               int source_length)
+    : script(s),
+      toplevel(0, source_length, 1, isolate->factory()->empty_string()) {}
+
+Coverage* Coverage::Collect(Isolate* isolate) {
   SharedToCounterMap counter_map;
 
   // Feed invocation count into the counter map.
   if (isolate->IsCodeCoverageEnabled()) {
     // Feedback vectors are already listed to prevent losing them to GC.
     Handle<ArrayList> list =
         Handle<ArrayList>::cast(isolate->factory()->code_coverage_list());
     for (int i = 0; i < list->Length(); i++) {
       FeedbackVector* vector = FeedbackVector::cast(list->Get(i));
       SharedFunctionInfo* shared = vector->shared_function_info();
@@ skipping 10 matching lines @@
       FeedbackVector* vector = FeedbackVector::cast(current_obj);
       SharedFunctionInfo* shared = vector->shared_function_info();
       if (!shared->IsSubjectToDebugging()) continue;
       uint32_t count = static_cast<uint32_t>(vector->invocation_count());
       counter_map.Add(shared, count);
     }
   }
 
   // Iterate shared function infos of every script and build a mapping
   // between source ranges and invocation counts.
-  std::vector<Coverage::ScriptData> result;
+  Coverage* result = new Coverage();
   Script::Iterator scripts(isolate);
   while (Script* script = scripts.Next()) {
     // Dismiss non-user scripts.
     if (script->type() != Script::TYPE_NORMAL) continue;
 
     // Create and add new script data.
-    int source_length = String::cast(script->source())->length();
-    result.emplace_back(Handle<Script>(script, isolate), source_length);
+    int source_end = String::cast(script->source())->length();
+    Handle<Script> script_handle(script, isolate);
+    result->emplace_back(isolate, script_handle, source_end);
 
     std::vector<SharedFunctionInfo*> sorted;
 
     {
       // Collect a list of shared function infos sorted by start position.
       // Shared function infos are usually already sorted. Except for classes.
       // If the start position is the same, sort from outer to inner function.
-      HandleScope scope(isolate);
-      SharedFunctionInfo::ScriptIterator infos(Handle<Script>(script, isolate));
+      SharedFunctionInfo::ScriptIterator infos(script_handle);
       while (SharedFunctionInfo* info = infos.Next()) sorted.push_back(info);
       std::sort(sorted.begin(), sorted.end(), CompareSharedFunctionInfo);
     }
 
-    std::vector<Range*> stack;
-    stack.push_back(&result.back().toplevel);
+    std::vector<CoverageRange*> stack;
+    stack.push_back(&result->back().toplevel);
 
     // Use sorted list to reconstruct function nesting.
     for (SharedFunctionInfo* info : sorted) {
       int start = StartPosition(info);
       int end = info->end_position();
       uint32_t count = counter_map.Get(info);
       if (info->is_toplevel()) {
         // Top-level function is available.
         DCHECK_EQ(1, stack.size());
-        result.back().toplevel.start = start;
-        result.back().toplevel.end = end;
-        result.back().toplevel.count = count;
+        result->back().toplevel.start = start;
+        result->back().toplevel.end = end;
+        result->back().toplevel.count = count;
       } else {
         // The shared function infos are sorted by start.
         DCHECK_LE(stack.back()->start, start);
         // Drop the stack to the outer function.
         while (start >= stack.back()->end) stack.pop_back();
-        Range* outer = stack.back();
+        CoverageRange* outer = stack.back();
         // New nested function.
         DCHECK_LE(end, outer->end);
-        outer->inner.emplace_back(start, end, count);
-        Range& nested = outer->inner.back();
-        String* name = info->DebugName();
-        nested.name.resize(name->length());
-        String::WriteToFlat(name, nested.name.data(), 0, name->length());
-        stack.push_back(&nested);
+        Handle<String> name(info->DebugName(), isolate);

[kozy, 2017/02/15 16:33:41]

Why GC couldn't happen for example here? Is it safe to use raw pointers to
SharedFunctionInfos?

[Yang, 2017/02/15 16:42:41]

Yes. No GC can happen. We assert that in the SharedToCounterMap as scope.

+        outer->inner.emplace_back(start, end, count, name);
+        stack.push_back(&outer->inner.back());
       }
     }
   }
   return result;
 }
 
-void Coverage::EnablePrecise(Isolate* isolate) {
-  HandleScope scope(isolate);
-  // Remove all optimized function. Optimized and inlined functions do not
-  // increment invocation count.
-  Deoptimizer::DeoptimizeAll(isolate);
-  // Collect existing feedback vectors.
-  std::vector<Handle<FeedbackVector>> vectors;
-  {
-    HeapIterator heap_iterator(isolate->heap());
-    while (HeapObject* current_obj = heap_iterator.next()) {
-      if (!current_obj->IsFeedbackVector()) continue;
-      FeedbackVector* vector = FeedbackVector::cast(current_obj);
-      SharedFunctionInfo* shared = vector->shared_function_info();
-      if (!shared->IsSubjectToDebugging()) continue;
-      vector->clear_invocation_count();
-      vectors.emplace_back(vector, isolate);
+void Coverage::TogglePrecise(Isolate* isolate, bool enable) {
+  if (enable) {
+    HandleScope scope(isolate);
+    // Remove all optimized function. Optimized and inlined functions do not
+    // increment invocation count.
+    Deoptimizer::DeoptimizeAll(isolate);
+    // Collect existing feedback vectors.
+    std::vector<Handle<FeedbackVector>> vectors;
+    {
+      HeapIterator heap_iterator(isolate->heap());
+      while (HeapObject* current_obj = heap_iterator.next()) {
+        if (!current_obj->IsFeedbackVector()) continue;
+        FeedbackVector* vector = FeedbackVector::cast(current_obj);
+        SharedFunctionInfo* shared = vector->shared_function_info();
+        if (!shared->IsSubjectToDebugging()) continue;
+        vector->clear_invocation_count();
+        vectors.emplace_back(vector, isolate);
+      }
     }
+    // Add collected feedback vectors to the root list lest we lose them to GC.
+    Handle<ArrayList> list =
+        ArrayList::New(isolate, static_cast<int>(vectors.size()));
+    for (const auto& vector : vectors) list = ArrayList::Add(list, vector);
+    isolate->SetCodeCoverageList(*list);
+  } else {
+    isolate->SetCodeCoverageList(isolate->heap()->undefined_value());
   }
-  // Add collected feedback vectors to the root list lest we lose them to GC.
-  Handle<ArrayList> list =
-      ArrayList::New(isolate, static_cast<int>(vectors.size()));
-  for (const auto& vector : vectors) list = ArrayList::Add(list, vector);
-  isolate->SetCodeCoverageList(*list);
-}
-
-void Coverage::DisablePrecise(Isolate* isolate) {
-  isolate->SetCodeCoverageList(isolate->heap()->undefined_value());
 }
 
 }  // namespace internal
 }  // namespace v8