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  • [gentoo-dev] time64 ABI fix coming to upstream glibc

    From Florian Weimer@21:1/5 to All on Thu May 2 12:40:01 2024
    The <utmp.h> and <utmp.h> headers had a bug that the on-disk structures
    defined there could change size on some targets when _TIME_BITS was set
    to 64. This is obviously wrong because the files are not going to
    magically change their layout because the application accessing them was
    built in a specific way. We're going to fix this in glibc upstream on
    the stable release branches, going all the way back to glibc 3.34 (the
    first release with this kind of time64 support). After the fix, the
    _TIME_BITS definition will no longer impact struct layout. Usually,
    that means epoch fields are 32-bits wide, to match co-installable architectures.

    To extend the usable life-time of these interfaces somewhat, glibc 2.40
    changes epoch fields to unsigned types in these structures. This change
    is specific to the upcoming glibc 2.40 release, I do not plan to
    backport it.

    Thanks,
    Florian

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  • From Sam James@21:1/5 to Florian Weimer on Fri May 3 06:40:01 2024
    Florian Weimer <fweimer@redhat.com> writes:

    The <utmp.h> and <utmp.h> headers had a bug that the on-disk structures defined there could change size on some targets when _TIME_BITS was set
    to 64. This is obviously wrong because the files are not going to
    magically change their layout because the application accessing them was built in a specific way. We're going to fix this in glibc upstream on
    the stable release branches, going all the way back to glibc 3.34 (the
    first release with this kind of time64 support). After the fix, the _TIME_BITS definition will no longer impact struct layout. Usually,
    that means epoch fields are 32-bits wide, to match co-installable architectures.

    To extend the usable life-time of these interfaces somewhat, glibc 2.40 changes epoch fields to unsigned types in these structures. This change
    is specific to the upcoming glibc 2.40 release, I do not plan to
    backport it.

    Thank you for the heads-up Florian. We haven't yet started our time64
    migration - the plan is to start playing with it over the next few
    months, so the timing has worked out well for us. We'll make sure the
    fixes are pulled in before we solidify anything beyond experiments.

    I'm trying not to wait *too* late to start, just in case we do end up
    finding any other problems like this, rather than finding them years
    down the line when it's too late to fix anything.


    Thanks,
    Florian

    thanks,
    sam

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