> According to printf(3):
>
> snprintf() and vsnprintf() will write at most size-1 of the characters
> printed into the output string (the size'th character then gets the ter-
> minating `\0'); if the return value is greater than or equal to the size
> argument, the string was too short and some of the printed characters
> were discarded. If size is zero, str may be a null pointer and no char-
> acters will be written; the number of bytes that would have been written
> excluding the terminating `\0' byte, or -1 on error, will be returned.
>
> and:
>
> The snprintf() and vsnprintf() functions return the number of characters
> that would have been output if the size were unlimited (again, not
> including the final `\0'). If an output or encoding error occurs, a
> val-
> ue of -1 is returned instead.
>
> I'm having trouble making snprintf return -1. I've tried stuff like:
>
> len = snprintf(str, 0, "%.-Z\n", 9);
> printf("%d", len);
>
> but that just prints `2'. Does snprintf ever return -1?
On some other systems, yes. On OpenBSD -- today -- it cannot return -1.
However, that is absolutely no excuse to go writing unportable code.
You must check for either ret > buflen or ret == -1 being a failure
condition.
