v8: add api for aborting on uncaught exception

Add v8::Isolate::SetAbortOnUncaughtException() so the user can be
notified when an uncaught exception has bubbled.

PR-URL: nodejs/node-v0.x-archive#8666
Reviewed-by: Trevor Norris <trev.norris@gmail.com>

Signed-off-by: Jeroen Ooms <jeroenooms@gmail.com>

include/v8.h

@@ -2841,6 +2841,17 @@ class V8EXPORT Isolate {
    */
   static Isolate* GetCurrent();
 
+  /**
+   * Custom callback used by embedders to help V8 determine if it should abort
+   * when it throws and no internal handler can catch the exception.
+   * If FLAG_abort_on_uncaught_exception is true, then V8 will abort if either:
+   * - no custom callback is set.
+   * - the custom callback set returns true.
+   * Otherwise it won't abort.
+   */
+  typedef bool (*abort_on_uncaught_exception_t)();
+  void SetAbortOnUncaughtException(abort_on_uncaught_exception_t callback);
+
   /**
    * Methods below this point require holding a lock (using Locker) in
    * a multi-threaded environment.

src/api.cc

@@ -5550,6 +5550,11 @@ void Isolate::Enter() {
   isolate->Enter();
 }
 
+void Isolate::SetAbortOnUncaughtException(
+      abort_on_uncaught_exception_t callback) {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  isolate->SetAbortOnUncaughtException(callback);
+}
 
 void Isolate::Exit() {
   i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);

src/isolate.cc

@@ -1152,18 +1152,26 @@ void Isolate::DoThrow(Object* exception, MessageLocation* location) {
         thread_local_top()->pending_message_end_pos_ = location->end_pos();
       }
 
-      // 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).
+      // If the abort-on-uncaught-exception flag is specified, and if the
+      // exception is not caught by JavaScript (even when an external handler is
+      // present).
       if (fatal_exception_depth == 0 &&
           FLAG_abort_on_uncaught_exception &&
           (report_exception || can_be_caught_externally)) {
-        fatal_exception_depth++;
-        fprintf(stderr, "%s\n\nFROM\n",
-          *MessageHandler::GetLocalizedMessage(message_obj));
-        PrintCurrentStackTrace(stderr);
-        OS::Abort();
+        // If the embedder didn't specify a custom uncaught exception callback,
+        // or if the custom callback determined that V8 should abort, then
+        // abort
+        bool should_abort = !abort_on_uncaught_exception_callback_ ||
+                             abort_on_uncaught_exception_callback_();
+        if (should_abort) {
+          fatal_exception_depth++;
+          // This flag is intended for use by JavaScript developers, so
+          // print a user-friendly stack trace (not an internal one).
+          fprintf(stderr, "%s\n\nFROM\n",
+            *MessageHandler::GetLocalizedMessage(message_obj));
+          PrintCurrentStackTrace(stderr);
+          OS::Abort();
+        }
       }
     } else if (location != NULL && !location->script().is_null()) {
       // We are bootstrapping and caught an error where the location is set
@@ -1339,6 +1347,10 @@ void Isolate::SetCaptureStackTraceForUncaughtExceptions(
   stack_trace_for_uncaught_exceptions_options_ = options;
 }
 
+void Isolate::SetAbortOnUncaughtException(
+      v8::Isolate::abort_on_uncaught_exception_t callback) {
+  abort_on_uncaught_exception_callback_ = callback;
+}
 
 bool Isolate::is_out_of_memory() {
   if (has_pending_exception()) {
@@ -1534,7 +1546,8 @@ Isolate::Isolate()
       date_cache_(NULL),
       context_exit_happened_(false),
       deferred_handles_head_(NULL),
-      optimizing_compiler_thread_(this) {
+      optimizing_compiler_thread_(this),
+      abort_on_uncaught_exception_callback_(NULL) {
   TRACE_ISOLATE(constructor);
 
   memset(isolate_addresses_, 0,

src/isolate.h

@@ -692,6 +692,9 @@ class Isolate {
       int frame_limit,
       StackTrace::StackTraceOptions options);
 
+  typedef bool (*abort_on_uncaught_exception_t)();
+  void SetAbortOnUncaughtException(abort_on_uncaught_exception_t callback);
+
   // Tells whether the current context has experienced an out of memory
   // exception.
   bool is_out_of_memory();
@@ -1292,6 +1295,8 @@ class Isolate {
   DeferredHandles* deferred_handles_head_;
   OptimizingCompilerThread optimizing_compiler_thread_;
 
+  abort_on_uncaught_exception_t abort_on_uncaught_exception_callback_;
+
   friend class ExecutionAccess;
   friend class HandleScopeImplementer;
   friend class IsolateInitializer;