Function display 

pub unsafe fn display<'a>(
    format: *const c_char,
    va_list: VaList<'a>,
) -> VaListDisplay<'a>

Returns an object that implements Display for safely printing formatting data. This is slightly less performant than using fmt_write, but may be the only option.

This shares the same caveats as fmt_write.

Safety

VaLists are very unsafe. The passed format and args parameter must be a valid printf format string.