fix gc backtrace

source/quickjs-internal.h

@@ -92,6 +92,10 @@
 // #define DUMP_OBJECTS    /* dump objects in JS_FreeContext */
 // #define DUMP_READ_OBJECT
 // #define DUMP_ROPE_REBALANCE
+/* dump GC ref stack push/pop with C backtrace on mismatch.
+   When HAVE_ASAN is also set, uses __sanitizer_print_stack_trace()
+   for symbolized output; otherwise falls back to execinfo backtrace(). */
+// #define DUMP_GC_REFS
 
 /* test the GC by forcing it before each object allocation */
 // #define FORCE_GC_AT_MALLOC