buildtools/third_party/libc++/generate_libcxx_headers.py

#!/usr/bin/env python3

# Copyright 2025 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import os
import pathlib
import subprocess

from typing import Optional

_CURRENT_DIR = pathlib.Path(__file__).parent
_OUT_OF_DATE_ERROR = """libcxx_headers.gni and third_party/libc++ are out of sync.

If you were messing around with the libc++ repository, run:
`buildtools/third_party/libc++/generate_libcxx_headers.py`

If the script doesn't resolve the error, file a bug to msta@ with reproduction details.
""".replace('\n', '$0x0A')


def _get_headers(include_dir: pathlib.Path) -> list[str]:
    headers = []
    for (dirpath, _, filenames) in os.walk(include_dir):
        dirpath = pathlib.Path(dirpath).relative_to(include_dir)
        for f in filenames:
            path = dirpath / f
            if f != 'CMakeLists.txt' and '__cxx03' not in path.parts:
                headers.append(str(path))
    headers.sort()
    return headers


def _get_libcxx_revision(path: pathlib.Path) -> Optional[str]:
    # On CoG this command will fail because libcxx is not a git repository.
    ps = subprocess.run(
        ['git', 'rev-parse', 'HEAD'],
        cwd=path,
        check=False,
        stdout=subprocess.PIPE,
        text=True,
    )
    if ps.returncode == 0:
        return ps.stdout.strip()


def _write_headers(path: pathlib.Path, headers: list[str],
                   libcxx_revision: Optional[str]):
    lines = [f'  "//third_party/libc++/src/include/{hdr}",' for hdr in headers]
    header_lines = '\n'.join(lines)
    if libcxx_revision is None:
        assertion = ''
    else:
        assertion = f"""
assert(
    libcxx_revision == "{libcxx_revision}",
    "{_OUT_OF_DATE_ERROR}")
"""
    path.write_text(f"""# Copyright 2025 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# DO NOT EDIT. This file is generated.
# This file should automatically be generated by the auto-roller.
# https://autoroll.skia.org/r/libcxx-chromium
# To manually regenerate, run:
# buildtools/third_party/libc++/generate_libcxx_headers.py

import("//buildtools/deps_revisions.gni")
{assertion}
libcxx_headers = [
{header_lines}
]
""")


if __name__ == '__main__':
    libcxx = _CURRENT_DIR / '../../../third_party/libc++/src'
    _write_headers(
        _CURRENT_DIR / 'libcxx_headers.gni',
        _get_headers(libcxx / 'include'),
        _get_libcxx_revision(libcxx),
    )