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Typically part of a "version string": $ python3 Python 3.10.7 (main, Jan 1 1970, 00:00:01) [GCC 11.3.0] on linux Type "help", "copyright", "credit

by mbakke 3y ago

Typically part of a "version string": $ python3 Python 3.10.7 (main, Jan 1 1970, 00:00:01) [GCC 11.3.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> Perhaps a relic from when software had to be manually updated?

oever 3y ago
On NixOS, I think the release time or commit time is used: $ python3 Python 3.10.11 (main, Apr 4 2023, 22:10:32) [GCC 12.2.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> That is more useful than the build time.
- mbakke 3y ago
  How is that possible? Is nixpkgs an input to the Python derivation? Or do packagers "hard code" a value every time they modify the Python build code? Automated tooling that sets it after pull requests? Something else? :-)
  - Smaug123 3y ago
    GCC respects SOURCE_DATE_EPOCH, and Nixpkgs has specific support for setting that environment variable: https://github.com/NixOS/nixpkgs/blob/92fdbd284c262f3e478033e4b41029dc160b7812/pkgs/build-support/setup-hooks/set-source-date-epoch-to-latest.sh#L12 https://github.com/NixOS/nixpkgs/blob/92fdbd284c262f3e478033... (although I haven't proved that this is actually how it works for cpython's build). Irrelevant spelunking details follow: That string is output by cpython to contain the contents of the __DATE__ C macro (https://github.com/python/cpython/blob/fa35b9e89b2e207fc8bae9eb0284260d0d922e7a/Modules/main.c#L192 https://github.com/python/cpython/blob/fa35b9e89b2e207fc8bae... which calls to https://github.com/python/cpython/blob/fa35b9e89b2e207fc8bae9eb0284260d0d922e7a/Modules/getbuildinfo.c#L45 https://github.com/python/cpython/blob/fa35b9e89b2e207fc8bae... which uses the __DATE__ macro at https://github.com/python/cpython/blob/fa35b9e89b2e207fc8bae9eb0284260d0d922e7a/Modules/getbuildinfo.c#L14 https://github.com/python/cpython/blob/fa35b9e89b2e207fc8bae... ). Cpython is defined in nixpkgs at https://github.com/NixOS/nixpkgs/blob/92fdbd284c262f3e478033e4b41029dc160b7812/pkgs/development/interpreters/python/cpython/default.nix https://github.com/NixOS/nixpkgs/blob/92fdbd284c262f3e478033... which I imagine (but haven't proved) uses GCC.
    - mbakke 3y ago
      Thank you! Setting SOURCE_DATE_EPOCH to the most recent file timestamp found in the source input is a clever hack.
  - oever 3y ago
    2023-04-04T22:10:32 is the timestamp of Python-3.10.11/Misc/NEWS from https://www.python.org/ftp/python/3.10.11/Python-3.10.11.tar.xz https://www.python.org/ftp/python/3.10.11/Python-3.10.11.tar...
  - raboof 3y ago
    The source for the cpython build is the release tarball (https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/interpreters/python/cpython/default.nix#L155 https://github.com/NixOS/nixpkgs/blob/master/pkgs/developmen...). In that case, NixOS sets SOURCE_DATE_EPOCH (which I suspect will be picked up by the python build) to the latest timestamp found in that archive (https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/setup-hooks/set-source-date-epoch-to-latest.sh https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-supp...)

by mbakke 3y ago

oever 3y ago

On NixOS, I think the release time or commit time is used: $ python3 Python 3.10.11 (main, Apr 4 2023, 22:10:32) [GCC 12.2.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> That is more useful than the build time.

mbakke 3y ago
How is that possible? Is nixpkgs an input to the Python derivation? Or do packagers "hard code" a value every time they modify the Python build code? Automated tooling that sets it after pull requests? Something else? :-)
- Smaug123 3y ago
  GCC respects SOURCE_DATE_EPOCH, and Nixpkgs has specific support for setting that environment variable: https://github.com/NixOS/nixpkgs/blob/92fdbd284c262f3e478033e4b41029dc160b7812/pkgs/build-support/setup-hooks/set-source-date-epoch-to-latest.sh#L12 https://github.com/NixOS/nixpkgs/blob/92fdbd284c262f3e478033... (although I haven't proved that this is actually how it works for cpython's build). Irrelevant spelunking details follow: That string is output by cpython to contain the contents of the __DATE__ C macro (https://github.com/python/cpython/blob/fa35b9e89b2e207fc8bae9eb0284260d0d922e7a/Modules/main.c#L192 https://github.com/python/cpython/blob/fa35b9e89b2e207fc8bae... which calls to https://github.com/python/cpython/blob/fa35b9e89b2e207fc8bae9eb0284260d0d922e7a/Modules/getbuildinfo.c#L45 https://github.com/python/cpython/blob/fa35b9e89b2e207fc8bae... which uses the __DATE__ macro at https://github.com/python/cpython/blob/fa35b9e89b2e207fc8bae9eb0284260d0d922e7a/Modules/getbuildinfo.c#L14 https://github.com/python/cpython/blob/fa35b9e89b2e207fc8bae... ). Cpython is defined in nixpkgs at https://github.com/NixOS/nixpkgs/blob/92fdbd284c262f3e478033e4b41029dc160b7812/pkgs/development/interpreters/python/cpython/default.nix https://github.com/NixOS/nixpkgs/blob/92fdbd284c262f3e478033... which I imagine (but haven't proved) uses GCC.
  - mbakke 3y ago
    Thank you! Setting SOURCE_DATE_EPOCH to the most recent file timestamp found in the source input is a clever hack.
- oever 3y ago
  2023-04-04T22:10:32 is the timestamp of Python-3.10.11/Misc/NEWS from https://www.python.org/ftp/python/3.10.11/Python-3.10.11.tar.xz https://www.python.org/ftp/python/3.10.11/Python-3.10.11.tar...
- raboof 3y ago
  The source for the cpython build is the release tarball (https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/interpreters/python/cpython/default.nix#L155 https://github.com/NixOS/nixpkgs/blob/master/pkgs/developmen...). In that case, NixOS sets SOURCE_DATE_EPOCH (which I suspect will be picked up by the python build) to the latest timestamp found in that archive (https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-support/setup-hooks/set-source-date-epoch-to-latest.sh https://github.com/NixOS/nixpkgs/blob/master/pkgs/build-supp...)