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Prepare the runtime build scripts for Python 3.15 - #2154
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This prepares the scripts used to compile the Python runtime binaries for Python 3.15. It does not add Python 3.15 support to the buildpack itself, which will follow in a later PR once Python 3.15.0 has been released (expected 2026-10-09) and its binaries built and uploaded. Python 3.15 no longer falls back to the bundled `libmpdec` when the system library is missing, which would otherwise cause the `_decimal` module to silently not be built: https://docs.python.org/3.15/whatsnew/3.15.html#build-changes We can't use the system package yet, since Ubuntu 24.04 doesn't currently ship `libmpdec-dev`. We've requested that it be re-added (https://bugs.launchpad.net/ubuntu/+source/mpdecimal/+bug/2167730), but even once it is, it must first be rolled out to all base images. So for now we explicitly opt in to the bundled copy using `--without-system-libmpdec`, with a TODO to switch later. The runtime test script now imports `_decimal` and `_hashlib` directly, since `decimal` and `hashlib` fall back to other implementations if their C modules weren't built, which would hide a broken build. It also imports `curses.panel`, since `curses` doesn't import `_curses_panel`, and now runs the `compression.zstd` check for all versions that have it rather than only 3.14. Tested by compiling Python 3.15.0rc3 for arm64 on Heroku-24 and running the runtime test script against the result. (This used a modified copy of the build script, since release candidates are published under a different URL to final releases, and we intentionally don't support them in the buildpack itself.) GUS-W-20591263.
edmorley
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October 8, 2026 14:24
edmorley
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October 8, 2026 14:24
Malax
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Oct 8, 2026
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This prepares the scripts used to compile the Python runtime binaries for Python 3.15. It does not add Python 3.15 support to the buildpack itself, which will follow in a later PR once Python 3.15.0 has been released (expected 2026-10-09) and its binaries built and uploaded.
Python 3.15 no longer falls back to the bundled
libmpdecwhen the system library is missing, which would otherwise cause the_decimalmodule to silently not be built:https://docs.python.org/3.15/whatsnew/3.15.html#build-changes
We can't use the system package yet, since Ubuntu 24.04 doesn't currently ship
libmpdec-dev. We've requested that it be re-added (https://bugs.launchpad.net/ubuntu/+source/mpdecimal/+bug/2167730), but even once it is, it must first be rolled out to all base images. So for now we explicitly opt in to the bundled copy using--without-system-libmpdec, with a TODO to switch later.The runtime test script now imports
_decimaland_hashlibdirectly, sincedecimalandhashlibfall back to other implementations if their C modules weren't built, which would hide a broken build. It also importscurses.panel, sincecursesdoesn't import_curses_panel, and now runs thecompression.zstdcheck for all versions that have it rather than only 3.14.Tested by compiling Python 3.15.0rc3 for arm64 on Heroku-24 and running the runtime test script against the result. (This used a modified copy of the build script, since release candidates are published under a different URL to final releases, and we intentionally don't support them in the buildpack itself.)
GUS-W-20591263.