Apply and read errors

src/lisp_string.c

@@ -22,13 +22,18 @@ LispVal *make_lisp_string(const char *data, size_t length, bool take,
 LispVal *lisp_sprintf(const char *format, ...) {
     va_list args;
     va_start(args, format);
+    LispVal *s = lisp_vsprintf(format, args);
+    va_end(args);
+    return s;
+}
+
+LispVal *lisp_vsprintf(const char *format, va_list args) {
     va_list args2;
     va_copy(args2, args);
     int needed = vsnprintf(NULL, 0, format, args2);
     va_end(args2);
     char *buffer = lisp_malloc(needed + 1);
     int printed = vsnprintf(buffer, needed + 1, format, args);
-    va_end(args);
     assert(printed == needed);
     return make_lisp_string(buffer, printed, true, false);
 }