1 files changed, 9 insertions, 7 deletions
diff --git a/JavaScriptCore/runtime/RegExpPrototype.cpp b/JavaScriptCore/runtime/RegExpPrototype.cpp
index bbc9e85..5f9d357 100644
--- a/JavaScriptCore/runtime/RegExpPrototype.cpp
+++ b/JavaScriptCore/runtime/RegExpPrototype.cpp
@@ -91,7 +91,7 @@ JSValue JSC_HOST_CALL regExpProtoFuncCompile(ExecState* exec, JSObject*, JSValue
     }
 
     if (!regExp->isValid())
-        return throwError(exec, SyntaxError, UString("Invalid regular expression: ").append(regExp->errorMessage()));
+        return throwError(exec, SyntaxError, makeString("Invalid regular expression: ", regExp->errorMessage()));
 
     asRegExpObject(thisValue)->setRegExp(regExp.release());
     asRegExpObject(thisValue)->setLastIndex(0);
@@ -106,15 +106,17 @@ JSValue JSC_HOST_CALL regExpProtoFuncToString(ExecState* exec, JSObject*, JSValu
         return throwError(exec, TypeError);
     }
 
-    UString result = "/" + asRegExpObject(thisValue)->get(exec, exec->propertyNames().source).toString(exec);
-    result.append('/');
+    char postfix[5] = { '/', 0, 0, 0, 0 };
+    int index = 1;
     if (asRegExpObject(thisValue)->get(exec, exec->propertyNames().global).toBoolean(exec))
-        result.append('g');
+        postfix[index++] = 'g';
     if (asRegExpObject(thisValue)->get(exec, exec->propertyNames().ignoreCase).toBoolean(exec))
-        result.append('i');
+        postfix[index++] = 'i';
     if (asRegExpObject(thisValue)->get(exec, exec->propertyNames().multiline).toBoolean(exec))
-        result.append('m');
-    return jsNontrivialString(exec, result);
+        postfix[index] = 'm';
+    UString source = asRegExpObject(thisValue)->get(exec, exec->propertyNames().source).toString(exec);
+    // If source is empty, use "/(?:)/" to avoid colliding with comment syntax
+    return jsNontrivialString(exec, makeString("/", source.size() ? source : UString("(?:)"), postfix));
 }
 
 } // namespace JSC