Date: Sun, 05 Jun 2011 21:17:45 +0100 From: Ben Laurie <ben@links.org> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: hackers@freebsd.org Subject: Re: int64_t and printf Message-ID: <4DEBE469.5060305@links.org> In-Reply-To: <11705.1307298084@critter.freebsd.dk> References: <11705.1307298084@critter.freebsd.dk>
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On 05/06/2011 19:21, Poul-Henning Kamp wrote:
> In message <4DEBC741.1020200@links.org>, Ben Laurie writes:
>
>> So, for example int64_t has no printf modifier I am aware of. Likewise
>> its many friends.
>
>> but I have no idea where to put such a thing in FreeBSD. Opinions?
>
> I have totally given up on this mess.
>
> At best you get incredibly messy source code, at worst you waste a
> lot of time figuring out why who to define stuff to make some platform
> you have only heard rumours about behave.
>
> I have therefore resorted to printf'ing any typedefed integer type using
> "%jd" and an explicit cast to (intmax_t):
>
> printf("%-30s -> %jd -> %s\n", s, (intmax_t)t, buf);
>
> If some system introduces int512_t that may not be optimal, but
> since printf is a pretty slow operation anyway, I doubt it will
> hurt even half as much as the alternative.
My objection to this approach is the lack of type-safety - t could be
anything and this would continue to work.
Using PRId64 at least ensures that t is of an appropriate type.
One way to get the best of both worlds is to at least ensure that t is
of the type you think it is before casting, but this also leads to messy
code - the best I can think of would look like
printf("%-30s -> %jd -> %s\n", s, cast(int64_t, intmax_t, t), buf);
Is this really better than
printf("%-30s -> %" PRId64 " -> %s\n", s, t, buf);
? Mere character count would suggest not.
Providing a better printf seems like an even smarter idea, e.g.
printf("%-30s -> %I64d -> %s\n", s, t, buf);
--
http://www.apache-ssl.org/ben.html http://www.links.org/
"There is no limit to what a man can do or how far he can go if he
doesn't mind who gets the credit." - Robert Woodruff
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