#!/usr/bin/python3
# Gather the names of all dynamic linkers in the glibc source tree.
# Copyright (C) 2021 Free Software Foundation, Inc.
# This file is part of the GNU C Library.
#
# The GNU C Library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# The GNU C Library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with the GNU C Library; if not, see
# <https://www.gnu.org/licenses/>.

"""Gather dynamic linker names.

This script scans the glibc source tree for shlib-versions files and
extracts the dynamic linker name from them.  I writes a header file
which defines an RTLD_ALL_NAMES macro.

"""

import argparse
import os
import re
import sys

# The dynamic linker name is optionally followed by a symbol version
# baseline.
RE_LD = re.compile(r'^ld=(\S+)(?:$|\s)')

def get_rtld_name(path):
    """Extract the ld= line from the file at PATH and return the ld.so name."""
    with open(path) as inp:
        for line in inp:
            match = RE_LD.match(line)
            if match is not None:
                rtld_name, = match.groups()
                if not rtld_name:
                    sys.stderr.write('{}: error: invalid rtld name: {!r}\n'
                                     .format(path, line))
                    sys.exit(1)
                return rtld_name
    # Nothing found.  Use the default.
    return None

def write_deps(directories, files, deps, output):
    """Write makefile dependency information for the file OUTPUT to DEPS."""
    with open(deps, 'w') as outp:
        outp.write(output)
        outp.write(': \\\n')

        for entry in directories + files:
            outp.write('  ')
            outp.write(entry)
            outp.write(' \\\n')
        outp.write('\n')

def write_output(rtld_names, path):
    """Writes a header file with the names list to PATH."""
    with open(path, 'w') as outp:
        outp.write('/* This file is automatically generated by ')
        our_name = os.path.basename(__file__)
        outp.write(our_name)
        outp.write('.\n   Do not edit.  */\n\n')

        outp.write('#define RTLD_ALL_NAMES \\\n')
        for name in rtld_names:
            outp.write('  "')
            outp.write(name)
            outp.write('\\0" \\\n')
        # An empty string terminates the list.
        outp.write('  ""\n')

def main():
    """The main entry point."""
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('--deps',
                        help='Dependency information for make',
                        type=str, required=True)
    parser.add_argument('--root',
                        help='Root directory of the source tree',
                        type=str, required=True)
    parser.add_argument('--output',
                        help='Generated source file with the ',
                        type=str, required=True)
    opts = parser.parse_args(sys.argv[1:])

    # The name of the file we are looking for.

    shlib_versions = 'shlib-versions'

    # This is used to generate directory dependencies, so that newly
    # added shlib-versions files will be found.
    directories = []

    # The default file does not live in a sysdeps subdirectory.
    files = [os.path.join(opts.root, shlib_versions)]

    # More files come from the sysdeps subdirectory.
    for dirpath, dirnames, filenames in os.walk(
            os.path.join(opts.root, 'sysdeps')):
        if shlib_versions in filenames:
            files.append(os.path.join(dirpath, shlib_versions))
        else:
            directories.append(dirpath)

    # Normalize the generated output.
    directories.sort()
    files.sort()
    write_deps(directories, files, opts.deps, opts.output)

    rtld_names = set()
    for path in files:
        name = get_rtld_name(path)
        if name is not None:
            rtld_names.add(name)

    write_output(sorted(rtld_names), opts.output)

if __name__ == "__main__":
    main()