[debug] support break points on API functions.

R=jgruber@chromium.org

Bug: v8:178
Change-Id: I1cabed9aa2a04f86e582ba09742b2e2857a40f27
Reviewed-on: https://chromium-review.googlesource.com/956045Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51830}

src/debug/debug.cc

@@ -1927,7 +1927,7 @@ bool Debug::AllFramesOnStackAreBlackboxed() {
 
 bool Debug::CanBreakAtEntry(Handle<SharedFunctionInfo> shared) {
   // Allow break at entry for builtin functions.
-  if (shared->native()) {
+  if (shared->native() || shared->IsApiFunction()) {
     // Functions that are subject to debugging can have regular breakpoints.
     DCHECK(!shared->IsSubjectToDebugging());
     return true;

test/cctest/test-debug.cc

@@ -1416,6 +1416,88 @@ TEST(BreakPointBuiltinNewContext) {
   CheckDebuggerUnloaded();
 }
 
+void NoOpFunctionCallback(const v8::FunctionCallbackInfo<v8::Value>& args) {
+  args.GetReturnValue().Set(v8_num(2));
+}
+
+TEST(BreakPointApiFunction) {
+  DebugLocalContext env;
+  v8::HandleScope scope(env->GetIsolate());
+
+  SetDebugEventListener(env->GetIsolate(), DebugEventBreakPointHitCount);
+
+  i::Handle<i::BreakPoint> bp;
+
+  v8::Local<v8::FunctionTemplate> function_template =
+      v8::FunctionTemplate::New(env->GetIsolate(), NoOpFunctionCallback);
+
+  v8::Local<v8::Function> function =
+      function_template->GetFunction(env.context()).ToLocalChecked();
+
+  env->Global()->Set(env.context(), v8_str("f"), function).ToChecked();
+
+  // === Test simple builtin ===
+  break_point_hit_count = 0;
+
+  // Run with breakpoint.
+  bp = SetBreakPoint(function, 0);
+  ExpectInt32("f()", 2);
+  CHECK_EQ(1, break_point_hit_count);
+
+  ExpectInt32("f()", 2);
+  CHECK_EQ(2, break_point_hit_count);
+
+  // Run without breakpoints.
+  ClearBreakPoint(bp);
+  ExpectInt32("f()", 2);
+  CHECK_EQ(2, break_point_hit_count);
+
+  SetDebugEventListener(env->GetIsolate(), nullptr);
+  CheckDebuggerUnloaded();
+}
+
+TEST(BreakPointInlineApiFunction) {
+  i::FLAG_allow_natives_syntax = true;
+  DebugLocalContext env;
+  v8::HandleScope scope(env->GetIsolate());
+
+  SetDebugEventListener(env->GetIsolate(), DebugEventBreakPointHitCount);
+
+  i::Handle<i::BreakPoint> bp;
+
+  v8::Local<v8::FunctionTemplate> function_template =
+      v8::FunctionTemplate::New(env->GetIsolate(), NoOpFunctionCallback);
+
+  v8::Local<v8::Function> function =
+      function_template->GetFunction(env.context()).ToLocalChecked();
+
+  env->Global()->Set(env.context(), v8_str("f"), function).ToChecked();
+  CompileRun("function g() { return 1 +  f(); }");
+
+  // === Test simple builtin ===
+  break_point_hit_count = 0;
+
+  // Run with breakpoint.
+  bp = SetBreakPoint(function, 0);
+  ExpectInt32("g()", 3);
+  CHECK_EQ(1, break_point_hit_count);
+
+  ExpectInt32("g()", 3);
+  CHECK_EQ(2, break_point_hit_count);
+
+  CompileRun("%OptimizeFunctionOnNextCall(g)");
+  ExpectInt32("g()", 3);
+  CHECK_EQ(3, break_point_hit_count);
+
+  // Run without breakpoints.
+  ClearBreakPoint(bp);
+  ExpectInt32("g()", 3);
+  CHECK_EQ(3, break_point_hit_count);
+
+  SetDebugEventListener(env->GetIsolate(), nullptr);
+  CheckDebuggerUnloaded();
+}
+
 // Test that a break point can be set at a return store location.
 TEST(BreakPointConditionBuiltin) {
   i::FLAG_allow_natives_syntax = true;