Re: Proposed CHOST change for the 64bit time_t transition

[Bruno Haible <bruno@clisp.org>]

Paul Eggert wrote:
> I'd rather just switch, as Debian has.

I'd go one step further, and not only
  make the ABI transition without changing the canonical triplet,
but also
  make gcc and clang define -D_FILE_OFFSET_BITS=64 -D_TIME_BITS=64
  among their predefines.

Rationale:

  * We want that a user of a distro with the new ABI can build
    packages in the usual way:
      - ./configure; make; make install (when using Autoconf), or
      - make; make install  (when there is just a Makefile).
    This *requires* that gcc and clang get patched, as indicated
    above.
    (Only changing Debian-specific files or variables won't do it.)

  * Once this has been done, is there a need for a triplet change?
    Not in the toolchain, and not in the packages either.
    Needs that have been mentioned in [1][2]:

      - Users would like to know in which ABI they / their distro lives.
        This can be done through a property in /etc/os-release.

      - "risks incompatibility with other distributions" [2]
        What is the problem? Do we expect users to build binaries
        on 32-bit distro X and try to run them on 32-bit distro Y?
        Or do we expect binary package distributors (like Mozilla,
        videolan.org) to do so?
        It was my impression that this approach is doomed anyway,
        because so many shared libraries have different major version
        in distro X than in distro Y.
        And that such binary package distributors use flatpak, AppImage, etc.
        precisely to get out of this dilemma.

      - Building gcc and glibc might need some particular options.
        Such options can be documented without requiring a new triplet.

References:
[1] https://wiki.debian.org/ReleaseGoals/64bit-time
[2] https://wiki.gentoo.org/wiki/Project:Toolchain/time64_migration