Issue #2089 - Use JS engine stack if necessary when reporting errors

Based-on: m-c 996060

1 files changed, 29 insertions, 7 deletions

diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 938fcb2a33..6002d86ad5 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -5762,8 +5762,22 @@ JS_IsExceptionPending(JSContext* cx);
 extern JS_PUBLIC_API(bool)
 JS_GetPendingException(JSContext* cx, JS::MutableHandleValue vp);
 
+namespace JS {
+
+enum class ExceptionStackBehavior: bool {
+  // Do not capture any stack.
+  DoNotCapture,
+
+  // Capture the current JS stack when setting the exception. It may be
+  // retrieved by JS::GetPendingExceptionStack.
+  Capture
+};
+
+} // namespace JS
+
 extern JS_PUBLIC_API(void)
-JS_SetPendingException(JSContext* cx, JS::HandleValue v);
+JS_SetPendingException(JSContext* cx, JS::HandleValue v,
+                       JS::ExceptionStackBehavior behavior = JS::ExceptionStackBehavior::Capture);
 
 extern JS_PUBLIC_API(void)
 JS_ClearPendingException(JSContext* cx);
@@ -5790,6 +5804,7 @@ class JS_PUBLIC_API(AutoSaveExceptionState)
     bool wasOverRecursed;
     bool wasThrowing;
     RootedValue exceptionValue;
+    RootedObject exceptionStack;
 
   public:
     /*
@@ -5808,12 +5823,7 @@ class JS_PUBLIC_API(AutoSaveExceptionState)
      * Discard any stored exception state.
      * If this is called, the destructor is a no-op.
      */
-    void drop() {
-        wasPropagatingForcedReturn = false;
-        wasOverRecursed = false;
-        wasThrowing = false;
-        exceptionValue.setUndefined();
-    }
+    void drop();
 
     /*
      * Replace cx's exception state with the stored exception state. Then
@@ -5823,6 +5833,18 @@ class JS_PUBLIC_API(AutoSaveExceptionState)
     void restore();
 };
 
+/**
+ * Get the SavedFrame stack object captured when the pending exception was set
+ * on the JSContext. This fuzzily correlates with a `throw` statement in JS,
+ * although arbitrary JSAPI consumers or VM code may also set pending exceptions
+ * via `JS_SetPendingException`.
+ *
+ * This is not the same stack as `e.stack` when `e` is an `Error` object. (That
+ * would be JS::ExceptionStackOrNull).
+ */
+MOZ_MUST_USE JS_PUBLIC_API(JSObject*)
+GetPendingExceptionStack(JSContext* cx);
+
 } /* namespace JS */
 
 /* Deprecated API. Use AutoSaveExceptionState instead. */