Throw an exception in the sandbox when an external function throws

src/exports.c

@@ -118,7 +118,7 @@ BOOL init(const char* init, int alertOnError) {
     ctx = JS_NewContext(runtime);
     globalAlertOnError = alertOnError;
 
-    result = JS_Eval(ctx, init, strlen(init), "<evalScript>", JS_EVAL_TYPE_GLOBAL);
+    result = JS_Eval(ctx, init, strlen(init), "<initScript>", JS_EVAL_TYPE_GLOBAL);
     if (buildAndPrintError(result, alertOnError)) {
         JS_FreeValue(ctx, result);
         return FALSE;

src/myjs.js

@@ -21,15 +21,20 @@
 mergeInto(LibraryManager.library, {
   $externals__postset: "externals();",
   $externals: function () {
-    _callExternalFunction = (name, args) => {
+    _callExternalFunction = (name, args, isError) => {
       name = UTF8ToString(name);
       args = args !== null ? JSON.parse(UTF8ToString(args)) : [];
-      const result = Module["externalCall"](name, args);
-      if (!result) {
-        return null;
-      }
+      try {
+        const result = Module["externalCall"](name, args);
+        if (!result) {
+          return null;
+        }
 
-      return stringToNewUTF8(result);
+        return stringToNewUTF8(result);
+      } catch (error) {
+        Module["HEAPU8"][isError] = 1;
+        return stringToNewUTF8(error.message);
+      }
     };
   },
   callExternalFunction: function () {},

src/quickjs_extra.c

@@ -53,11 +53,12 @@ static JSValue js_dump(JSContext *ctx, JSValueConst this_val,
 }
 
 #define CALLEXTERNALFUNCTION JS_CFUNC_DEF("callExternalFunction", 2, js_callExternalFunction),
-extern const char* callExternalFunction(const char*, const char*);
+extern const char* callExternalFunction(const char*, const char*, char* isError);
 static JSValue js_callExternalFunction(JSContext *ctx, JSValueConst this_val,
                                        int argc, JSValueConst *argv)
 {
     const char *name, *str = NULL, *result;
+    char isError = 0;
     JSValue json, obj;
 
     if (argc < 1 || argc > 2) {
@@ -83,7 +84,7 @@ static JSValue js_callExternalFunction(JSContext *ctx, JSValueConst this_val,
         }
     }
 
-    result = callExternalFunction(name, str);
+    result = callExternalFunction(name, str, &isError);
     JS_FreeCString(ctx, name);
     JS_FreeCString(ctx, str);
 
@@ -91,7 +92,21 @@ static JSValue js_callExternalFunction(JSContext *ctx, JSValueConst this_val,
         return JS_UNDEFINED;
     }
 
-    obj = JS_ParseJSON(ctx, result, strlen(result), "<output>");
+    if (likely(!isError)) {
+        obj = JS_ParseJSON(ctx, result, strlen(result), "<callExternalFunction>");
+    } else {
+        obj = JS_NewError(ctx);
+        if (unlikely(JS_IsException(obj))) {
+            /* out of memory: throw JS_NULL to avoid recursing */
+            obj = JS_NULL;
+        } else {
+            JS_DefinePropertyValue(ctx, obj, JS_ATOM_message,
+                                   JS_NewString(ctx, result),
+                                   JS_PROP_WRITABLE | JS_PROP_CONFIGURABLE);
+        }
+
+        obj = JS_Throw(ctx, obj);
+    }
 #ifdef free
 #undef free
 #endif