We could change our imagine and throw out and give up "just a way".
We've already put Sleep and tried it.
#include// // // // // char* err_msg_002(const char *fmt, ...) { static char* result; static va_list ap; Sleep(1000); if ( set_level_error_msg <= level_error_msg ) return NULL; va_start(ap, fmt); result = err_doit_001(0, 0, fmt, ap); va_end(ap); return result; }