prebuilt-cpython/relocatable.py at main · python/prebuilt-cpython · GitHub

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"""Make a relocatable build of CPython.

This script is meant to serve two purposes:

1. Test/show different approaches to making a relocatable build of CPython.

2. Provide an easy way to test a relocatable build so fixes can get upstreamed.

"""

# /// script

# requires-python = ">=3.14"

# ///

import argparse

import os

import pathlib

import shutil

import subprocess

def placeholder_prefix() -> str:

"""Return the placeholder prefix used when building CPython."""

return "/the/knights/who/say/ni".ljust(255, "i")

def patch_path(output_dir: pathlib.Path, patch: str) -> None:

"""Replace placeholder prefixes with an eventual installation path."""

target = os.fsencode(pathlib.Path(patch).resolve())

placeholder = os.fsencode(placeholder_prefix())

if len(target) > len(placeholder):

raise ValueError(

f"resolved patch path is {len(target)} bytes; "

f"the maximum is {len(placeholder)} bytes"

)

for root, _, filenames in output_dir.walk():

for filename in filenames:

path = root / filename

if path.is_symlink():

continue

contents = path.read_bytes()

if placeholder not in contents:

continue

replacement = target

if b"\0" in contents:

replacement = target.ljust(len(placeholder), b"\0")

path.write_bytes(contents.replace(placeholder, replacement))

def patch_origin(output_dir: pathlib.Path) -> None:

"""Make installed ELF files load libraries relative to themselves."""

lib_dir = output_dir / "lib"

for root, _, filenames in output_dir.walk():

for filename in filenames:

path = root / filename

if path.is_symlink():

continue

with path.open("rb") as file:

if file.read(4) != b"\x7fELF":

continue

relative_lib = os.path.relpath(lib_dir, path.parent)

rpath = "$ORIGIN"

if relative_lib != ".":

rpath = f"{rpath}/{relative_lib}"

subprocess.run(

["patchelf", "--force-rpath", "--set-rpath", rpath, path],

check=True,

)

def run_configure(source_dir: pathlib.Path, build_dir: pathlib.Path) -> None:

"""Run `configure` in the build directory."""

configure = source_dir.resolve() / "configure"

build_dir.mkdir(parents=True, exist_ok=True)

subprocess.run(

[

configure,

f"--prefix={placeholder_prefix()}",

"--without-static-libpython",

cwd=build_dir,

check=True,

)

def run_make(source_dir: pathlib.Path, build_dir: pathlib.Path) -> None:

"""Run `make` in the build directory."""

subprocess.run(

["make", f"-j{os.process_cpu_count() or 1}", "-s"],

cwd=build_dir,

check=True,

)

def run_gather(

source_dir: pathlib.Path,

build_dir: pathlib.Path,

output_dir: pathlib.Path,

strategy: str,

install_dir: pathlib.Path,

) -> None:

"""Gather all the release files together."""

output_dir = output_dir.resolve()

if output_dir.exists():

shutil.rmtree(output_dir)

subprocess.run(

[

"make",

"-s",

"commoninstall",

f"prefix={output_dir}",

cwd=build_dir,

check=True,

)

if strategy == "origin":

# python-build-standalone also patches CPython's source, rewrites

# scripts and metadata, handles Mach-O, and ships shared libpython.

# Those are intentionally excluded from this post-build ELF experiment.

patch_origin(output_dir)

patch_path(output_dir, os.fspath(install_dir))

def parse_args(args: list[str] | None = None) -> argparse.Namespace:

parser = argparse.ArgumentParser()

subparsers = parser.add_subparsers(dest="command", required=True)

common_parser = argparse.ArgumentParser(add_help=False)

common_parser.add_argument(

"source_dir",

nargs="?",

type=pathlib.Path,

default=pathlib.Path.cwd(),

help="CPython source checkout (default: current directory)",

)

common_parser.add_argument(

"--build-dir",

type=pathlib.Path,

help="build directory (default: SOURCE_DIR/builddir)",

)

subparsers.add_parser("configure", parents=[common_parser], help="Run `configure`")

subparsers.add_parser("make", parents=[common_parser], help="Run `make`")

gather_parser = subparsers.add_parser(

"gather",

parents=[common_parser],

help="Gather all the release files together",

)

gather_parser.add_argument(

"--output",

dest="output_dir",

type=pathlib.Path,

help="distribution directory (default: SOURCE_DIR/dist)",

)

patch_group = gather_parser.add_mutually_exclusive_group(required=True)

patch_group.add_argument(

"--patch",

nargs="?",

const=None,

default=argparse.SUPPRESS,

type=pathlib.Path,

metavar="INSTALL_DIR",

help=(

"patch in the eventual install directory (default: OUTPUT); "

"relative paths resolve from the current directory"

)

patch_group.add_argument(

"--origin",

nargs="?",

const=None,

default=argparse.SUPPRESS,

type=pathlib.Path,

metavar="INSTALL_DIR",

help=(

"patch in the eventual install directory and use $ORIGIN for ELF "

"library lookup (default: OUTPUT; Linux only; requires patchelf)"

)

namespace = parser.parse_args(args)

if namespace.build_dir is None:

namespace.build_dir = namespace.source_dir / "builddir"

if namespace.command == "gather" and namespace.output_dir is None:

namespace.output_dir = namespace.source_dir / "dist"

if namespace.command == "gather":

if hasattr(namespace, "patch"):

namespace.patch_strategy = "patch"

install_dir = namespace.patch

else:

namespace.patch_strategy = "origin"

install_dir = namespace.origin

if install_dir is None:

install_dir = namespace.output_dir

namespace.install_dir = install_dir

return namespace

def main(args: list[str] | None = None) -> None:

namespace = parse_args(args)

match namespace.command:

case "configure":

run_configure(namespace.source_dir, namespace.build_dir)

case "make":

run_make(namespace.source_dir, namespace.build_dir)

case "gather":

run_gather(

namespace.source_dir,

namespace.build_dir,

namespace.output_dir,

namespace.patch_strategy,

namespace.install_dir,

)

case command:

raise ValueError(f"Unknown command: {command}")

if __name__ == "__main__":

main()

prebuilt-cpython/relocatable.py at main · python/prebuilt-cpython · GitHub

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