Add SetAbortOnUncaughtExceptionCallback API

The --abort-on-uncaught-exception command line switch makes
Isolate::Throw abort if the error being thrown cannot be caught by a
try/catch block.

Embedders may want to use other mechanisms than try/catch blocks to
handle uncaught exceptions. For instance, Node.js has "domain" objects
that have error handlers that can handle uncaught exception like
following:

var d = domain.create();

d.on('error', function onError(err) {
  console.log('Handling error');
});

d.run(function() {
  throw new Error("boom");
});

These error handlers are called by isolates' message listeners.

If --abort-on-uncaught-exception is *not* used, the isolate's
message listener will be called, which will in turn call the domain's
error handler. The process will output 'Handling error' and will exit
successfully (not due to an uncaught exception). This is the behavior
that Node.js users expect.

However, if --abort-on-uncaught-exception is used and when throwing an
error within a domain that has an error handler, the process will abort
and the domain's error handler will not be called. This is not the
behavior that Node.js users expect.

Having a SetAbortOnUncaughtExceptionCallback API allows embedders to
determine when it's not appropriate to abort and instead handle the
exception via the isolate's message listener.

In the example above, Node.js would set a custom callback with
SetAbortOnUncaughtExceptionCallback that would be implemented as
following (the sample code has been simplified to remove what's not
relevant to this change):

bool ShouldAbortOnUncaughtException(Isolate* isolate) {
  return !IsDomainActive();
}

Now when --abort-on-uncaught-exception is used, Isolate::Throw would
call that callback and determine that it should not abort if a domain
with an error handler is active. Instead, the isolate's message listener
would be called and the error would be handled by the domain's error
handler.

I believe this can also be useful for other embedders.

BUG=

R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/1375933003

Cr-Commit-Position: refs/heads/master@{#31111}

include/v8.h

@@ -5377,6 +5377,19 @@ class V8_EXPORT Isolate {
    */
   static Isolate* GetCurrent();
 
+  /**
+   * Custom callback used by embedders to help V8 determine if it should abort
+   * when it throws and no internal handler is predicted to catch the
+   * exception. If --abort-on-uncaught-exception is used on the command line,
+   * then V8 will abort if either:
+   * - no custom callback is set.
+   * - the custom callback set returns true.
+   * Otherwise, the custom callback will not be called and V8 will not abort.
+   */
+  typedef bool (*AbortOnUncaughtExceptionCallback)(Isolate*);
+  void SetAbortOnUncaughtExceptionCallback(
+      AbortOnUncaughtExceptionCallback callback);
+
   /**
    * Methods below this point require holding a lock (using Locker) in
    * a multi-threaded environment.

src/api.cc

@@ -7096,6 +7096,13 @@ void Isolate::Exit() {
 }
 
 
+void Isolate::SetAbortOnUncaughtExceptionCallback(
+    AbortOnUncaughtExceptionCallback callback) {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  isolate->SetAbortOnUncaughtExceptionCallback(callback);
+}
+
+
 Isolate::DisallowJavascriptExecutionScope::DisallowJavascriptExecutionScope(
     Isolate* isolate,
     Isolate::DisallowJavascriptExecutionScope::OnFailure on_failure)

src/isolate.cc

@@ -1008,13 +1008,21 @@ Object* Isolate::Throw(Object* exception, MessageLocation* location) {
       Handle<Object> message_obj = CreateMessage(exception_handle, location);
       thread_local_top()->pending_message_obj_ = *message_obj;
 
-      // If the abort-on-uncaught-exception flag is specified, abort on any
-      // exception not caught by JavaScript, even when an external handler is
-      // present.  This flag is intended for use by JavaScript developers, so
-      // print a user-friendly stack trace (not an internal one).
+      // For any exception not caught by JavaScript, even when an external
+      // handler is present:
+      // If the abort-on-uncaught-exception flag is specified, and if the
+      // embedder didn't specify a custom uncaught exception callback,
+      // or if the custom callback determined that V8 should abort, then
+      // abort.
       if (FLAG_abort_on_uncaught_exception &&
-          PredictExceptionCatcher() != CAUGHT_BY_JAVASCRIPT) {
-        FLAG_abort_on_uncaught_exception = false;  // Prevent endless recursion.
+          PredictExceptionCatcher() != CAUGHT_BY_JAVASCRIPT &&
+          (!abort_on_uncaught_exception_callback_ ||
+           abort_on_uncaught_exception_callback_(
+               reinterpret_cast<v8::Isolate*>(this)))) {
+        // Prevent endless recursion.
+        FLAG_abort_on_uncaught_exception = false;
+        // This flag is intended for use by JavaScript developers, so
+        // print a user-friendly stack trace (not an internal one).
         PrintF(stderr, "%s\n\nFROM\n",
                MessageHandler::GetLocalizedMessage(this, message_obj).get());
         PrintCurrentStackTrace(stderr);
@@ -1602,6 +1610,12 @@ void Isolate::SetCaptureStackTraceForUncaughtExceptions(
 }
 
 
+void Isolate::SetAbortOnUncaughtExceptionCallback(
+    v8::Isolate::AbortOnUncaughtExceptionCallback callback) {
+  abort_on_uncaught_exception_callback_ = callback;
+}
+
+
 Handle<Context> Isolate::native_context() {
   return handle(context()->native_context());
 }
@@ -1770,7 +1784,8 @@ Isolate::Isolate(bool enable_serializer)
       next_unique_sfi_id_(0),
 #endif
       use_counter_callback_(NULL),
-      basic_block_profiler_(NULL) {
+      basic_block_profiler_(NULL),
+      abort_on_uncaught_exception_callback_(NULL) {
   {
     base::LockGuard<base::Mutex> lock_guard(thread_data_table_mutex_.Pointer());
     CHECK(thread_data_table_);

src/isolate.h

@@ -655,6 +655,9 @@ class Isolate {
       int frame_limit,
       StackTrace::StackTraceOptions options);
 
+  void SetAbortOnUncaughtExceptionCallback(
+      v8::Isolate::AbortOnUncaughtExceptionCallback callback);
+
   enum PrintStackMode { kPrintStackConcise, kPrintStackVerbose };
   void PrintCurrentStackTrace(FILE* out);
   void PrintStack(StringStream* accumulator,
@@ -1325,6 +1328,9 @@ class Isolate {
 
   std::set<Cancelable*> cancelable_tasks_;
 
+  v8::Isolate::AbortOnUncaughtExceptionCallback
+      abort_on_uncaught_exception_callback_;
+
   friend class ExecutionAccess;
   friend class HandleScopeImplementer;
   friend class OptimizingCompileDispatcher;

test/cctest/test-api.cc

@@ -21865,3 +21865,34 @@ TEST(EstimatedContextSize) {
   LocalContext env;
   CHECK(50000 < env->EstimatedSize());
 }
+
+
+static int nb_uncaught_exception_callback_calls = 0;
+
+
+bool NoAbortOnUncaughtException(v8::Isolate* isolate) {
+  ++nb_uncaught_exception_callback_calls;
+  return false;
+}
+
+
+TEST(AbortOnUncaughtExceptionNoAbort) {
+  v8::Isolate* isolate = CcTest::isolate();
+  v8::HandleScope handle_scope(isolate);
+  v8::Handle<v8::ObjectTemplate> global_template =
+      v8::ObjectTemplate::New(isolate);
+  LocalContext env(NULL, global_template);
+
+  i::FLAG_abort_on_uncaught_exception = true;
+  isolate->SetAbortOnUncaughtExceptionCallback(NoAbortOnUncaughtException);
+
+  CompileRun("function boom() { throw new Error(\"boom\") }");
+
+  v8::Local<v8::Object> global_object = env->Global();
+  v8::Local<v8::Function> foo =
+      v8::Local<v8::Function>::Cast(global_object->Get(v8_str("boom")));
+
+  foo->Call(global_object, 0, NULL);
+
+  CHECK_EQ(1, nb_uncaught_exception_callback_calls);
+}