CMake Python build

Build recent version of Python from source and Python prerequisite libraries using CMake ExternalProject and Autotools. Tested with Python 3.10 ... 3.14 and newer.

This project is a thin use of CMake ExternalProject to build Python via Python project's Autotools scripts.

Build

cmake -B build --install-prefix=$HOME/python-local

cmake --build build

Optional: check that Python built-in libraries are working:

ctest --test-dir build -V

That makes binaries including: ~/python-local/bin/[python3,pip3]. If the system has graphical capabilities, this built Python will work with Matplotlib, etc.

Typical config log (just before install step) is like the following. In particular, lzma and ssl should not be missing.

The necessary bits to build these optional modules were not found:
_dbm                      _gdbm                     _tkinter
readline
To find the necessary bits, look in configure.ac and config.log.

Checked 112 modules (34 built-in, 73 shared, 1 n/a on linux-x86_64, 0 disabled, 4 missing, 0 failed on import)

Options

-Dfind=on : (default on) searches for these libraries and builds them if not present: bzip2 expat ffi lzma ssl zlib

To use system OpenSSL while building other prereqs:

cmake -Bbuild -Dfind=no -Dfind_ssl=yes

-DCMAKE_BUILD_TYPE=Release : build Python itself with optimization (default on). Building Python with optimization takes longer--about 2 minutes on a Mac Mini M1. Other libraries are always set to optimize.

Optionally, select Python version or URL like:

-Dpython_version="3.14.0a2" : select Python Git tag to build.

-Dpython_url="https://www.python.org/ftp/python/3.14.0/Python-3.14.0a2.tar.xz" : URL is automatically determined from the version, but can be overridden.

Why?

1. Getting Python can be tricky for license-restricted users e.g. government and corporations.
2. Building Python can be an arcane process without the automation of a high-level build system CMake.

Python uses Autotools except for Windows where Visual Studio is used. The libraries need to be built with specific options and the forums are full of suggestions for tweaking Python build scripts etc. This CMake project elides those issues.

standalone embedded Windows script

A separate CMake script for Windows-only that downloads and extracts a standalone embedded Python is at scripts/install-python.cmake.

Compilers

Tested on Linux and MacOS with compilers including:

• Apple Clang
• Linux: GCC 4.8 and newer

The CMakeLists.txt automatically forces "clang" on MacOS and "gcc" on Linux. This seemed to be the most robust choice, as Autotools failed to configure with choices like "gcc-version" and Intel "icx" took 100x longer than GCC to build.

Prereqs

Some low level prereqs aren't built by this project:

• libtool: dnf install libtool or brew install libtool-bin or apt install libtool-bin
• libssl: requires Perl, dnf install perl or brew install perl for FindBin.pm

OpenSSL: Python is compatible with a certain range of OpenSSL versions.

Alternatives

replace Python's Autotools scripts completely with CMake