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Re: Second draft of the Y2038 design document
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Arnd Bergmann <arnd at arndb dot de>
- Cc: <libc-alpha at sourceware dot org>, Albert ARIBAUD <albert dot aribaud at 3adev dot fr>
- Date: Thu, 28 Jan 2016 23:36:39 +0000
- Subject: Re: Second draft of the Y2038 design document
- Authentication-results: sourceware.org; auth=none
- References: <20160128204114 dot 6c7dbbf7 dot albert dot aribaud at 3adev dot fr> <alpine dot DEB dot 2 dot 10 dot 1601282059200 dot 6102 at digraph dot polyomino dot org dot uk> <2253786 dot S41ObuKQ66 at wuerfel>
On Fri, 29 Jan 2016, Arnd Bergmann wrote:
> On Thursday 28 January 2016 21:13:55 Joseph Myers wrote:
> > I don't think the classification of whether symbols are "Y2038-sensitive"
> > is useful.
> > The relevant question is: does the ABI to a function involve time_t,
> > whether directory or indirectly (e.g. through struct stat)? If it does, a
> > separate version is needed for _TIME_BITS=64. That includes functions
> > involving relative timestamps. And the notes "3. Regardless of the time_t
> > size, the function may not return a time_t value beyond Y2038." and "4.
> > Regardless of the time_t size, the function may not accept an time_t input
> > value beyond Y2038." simply seem wrong - functions should accept, and be
> > able to return, arbitrary valid time_t values.
> The only example I can think of that is limited in this way is utimes
> and kstat operating on file systems that cannot store time stamps beyond
> 2038, e.g. ext3. Setting a timestamp to a later date on such a file system
> currently has undefined behavior (wraparound in some way) and we are
> in the process of changing the kernel so it can instead either clamp
> the values to the minimum/maximum representable times, or return an
> error (the exact policy is not decided yet, but it should become
The main point here is that there is no glibc issue - glibc just passes
64-bit time_t values to / from the kernel and it's the kernel's job to
handle things appropriately if there are limitations from e.g.
Joseph S. Myers