[Asterisk-code-review] time: add support for time64 libcs (asterisk[master])

[Sebastian Kemper]

Attention is currently required from: Joshua Colp, George Joseph, Kevin Harwell, Philip Prindeville.
Sebastian Kemper has posted comments on this change. ( https://gerrit.asterisk.org/c/asterisk/+/16621 )

Change subject: time: add support for time64 libcs
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Patch Set 4:

(1 comment)

Patchset:

PS4: 
> I'm inclined to agree.  There are two paths forward: […]
Hi all,

I don't think there is a need to remove the use of PRIdN macros. But PRIdN macros do not have a relation to time_t. So using them for time_t is not the right way in my opinion.

a) time_t may be long or long long. But time_t may also be unsigned or float.
   - Does PRIdN approach take care of this? No.
   - Does "cast to (long long) and use %lld" approach take care of this? Yes.

b) Checking for __USE_TIME_BITS64 is also not portable. libcs may or may not declare it. Right now glibc does not declare it, yet its "arc" target, which is a 32 bit target, is already y2038 safe, it's using 64 bit time_t (long long).
   - Does PRIdN approach take care of this? No.
   - Does "cast to (long long) and use %lld" approach take care of this? Yes.

In 2013 OpenBSD discussed the y2038 issue at a convention (slides: [1]). Under "Simple instructions for conversions", "Systematic conversions" and "Userland audit" they suggest (long long) casts and %lld.

These slides were then discussed further (see [2]). When it came to printing time_t, the way I read it, the consensus was again to use casts to (long long) and %lld.

[1] https://www.openbsd.org/papers/eurobsdcon_2013_time_t/
[2] https://news.ycombinator.com/item?id=6466428

Kind regards,
Sebastian



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Gerrit-Project: asterisk
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