Re: *printf and zero size

Tom Lane wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > Tom, did you implement this functionality in *printf?
> > The size may be given as zero to find out how many characters are
> > needed; in this case, the str argument is ignored. Sprintf() and
> > vsprintf() effectively assume an infinite size.
>
> Where do you read that? The SUS says the opposite:
>
> If the value of n is zero on a call to snprintf(), an unspecified
> value less than 1 is returned.
>
> and that's what our code implements.

I got it from the BSD/OS manual page, and in the NetBSD manual page I
see:

If size is zero, nothing is written and str may be a NULL pointer.

and:

Upon successful completion snprintf() and vsnprintf() return the number
of characters that would have been written to a sufficiently sized str,
excluding the terminating NUL character.

but it seems this is some BSD'ism that we don't need to support if the
standard doesn't say so.

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