From 5fedc56343f55a822162f9c8fbe7e567508db054 Mon Sep 17 00:00:00 2001
From: "Erlend E. Aasland" <erlend@python.org>
Date: Mon, 9 Oct 2023 12:27:08 +0200
Subject: [PATCH] PEP 756: The CPython 3.13 build system

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+PEP: 756
+Title: The CPython 3.13 build system.
+Author: Erlend Egeberg Aasland <erlend@python.org>,
+        Zachary Ware <zach@python.org>
+Status: Draft
+Type: Standards Track
+Created: 09-Oct-2023
+Python-Version: 3.13
+
+
+Abstract
+========
+
+:pep:`755` summarized the problems with the CPython 3.12 build system.
+This PEP suggests a new build system be implemented for CPython 3.13,
+
+
+Motivation
+==========
+
+According to :pep:`755`, the biggest pain with the CPython 3.12 build system,
+is that consists of *two* hard-to-comprehend build systems:
+
+- The Windows build --- a collection of XML and BAT files
+- The \*nix build --- :file:`configure.ac` and :file:`Makefile.pre.in`
+
+Developers in the Windows camp find the GNU Autoconf code incomprehensible;
+developers in the \*nix camp find the XML files of the Windows build cryptic.
+
+Also according to :pep:`755`,
+the number one goal for a future build system is a unified build system.
+
+
+Rationale
+=========
+
+*TODO*
+
+
+Specification
+=============
+
+A build system will be implemented with the goals of :pep:`755` in mind:
+
+- a unified build system that works on all :pep:`11` supported platforms
+- correct and fast incremental builds
+- deterministic builds
+- it should be easy to constrain external dependencies
+- cross-compilation support
+- good quality documentation
+- an active community
+- being actively developed
+
+Contenders
+==========
+
+CMake
+-----
+
+CMake is implemented in C++,
+and is being actively developed as an open source project by Kitware
+under the BSD License 2.
+It has been around since 2000, and is currently at release 3.27.7.
+
+
+Meson
+-----
+
+Meson is implemented in Python,
+and is being actively developed as an open source project on GitHub
+under the Apache License 2.0.
+It has been around since 2013, and is currently at release 1.2.1.
+
+
+Bazel
+-----
+
+Bazel is implemented in Java,
+and is being actively developed as an open source project on GitHub by Google
+under the Apache License 2.0.
+It has been around since 2015, and is currently at release 6.0.0.
+
+
+Backwards Compatibility
+=======================
+
+A new build system will impose new bootstrapping constraints;
+this will affect how easy it will be to port Python to new architectures and platforms.
+A bootstrapping guide will be written for the devguide in order to mitigate this.
+
+
+Security Implications
+=====================
+
+*TODO*
+
+
+How to Teach This
+=================
+
+Documentation for core developers and contributors will be added to the docs and devguide.
+HowTo guides for specific use cases like deterministic builds and cross-building will be added.
+
+Most users, beginners included, are not not affected,
+as they are not expected to ever need to interface the build system.
+
+
+Reference Implementation
+========================
+
+*TODO: Add GitHub links*
+
+
+Rejected Ideas
+==============
+
+Keep the current dual build system
+----------------------------------
+
+Continuing to maintain the current dual build system will not harmonize
+with the most important desire amongst the core developers: a unified build system.
+
+The duality of the current build system is one of the biggest source of frustrations
+amongst core developers, contributors and distributors.
+
+
+Use a custom written build script
+---------------------------------
+
+Instead of chosing an existing build system,
+implement the new build system as a collection of hand-written scripts.
+
+The additional overhead of desiging a specification for such a build system,
+implementing, maintaining, and documenting it would be considerable compared
+to using an existing build system that comes complete with an implementation,
+documentation, and a support community.
+
+
+Open Issues
+===========
+
+Implement proof-of-concept build systems for the most promising contenders.
+
+
+Footnotes
+=========
+
+*TODO*
+
+
+Copyright
+=========
+
+This document is placed in the public domain or under the
+CC0-1.0-Universal license, whichever is more permissive.