#  define EXTEND_HWM_SET(p, n)                      \
        STMT_START {                                \
            SSize_t ix = (p) - PL_stack_base + (n); \
            if (ix > PL_curstackinfo->si_stack_hwm) \
                PL_curstackinfo->si_stack_hwm = ix; \
        } STMT_END