Fix broken shared library links in binaries/dylibs

fix_broken_links.py

# -----------------------------------------------------------------------------
# Copyright (C) 2014 Jason Gedge
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
# -----------------------------------------------------------------------------
"""Fix broken shared library links in binaries.

Makes use of otool and install_name_tool to apply changes. Additional search
paths can be given, but by default this utility looks in the following paths
for possible link replacements:

    - /usr/lib
    - /usr/local/lib
    - /usr/local/opt/lib
    - /usr/local/Cellar/**/lib (if Homebrew installed)

Note that this script is only useful if the ABI of the old and new links are
the same. Chances are though, if you run this script you already have a broken
library so changing the broken links may not affect you.
"""
import argparse
import os
import subprocess


# Get the library name for a given path
libname = lambda path: os.path.basename(path).partition('.')[0]


def execute(*args):
    """Execute a command and return the output.

    Args:
        *args: arguments to pass to the command

    Returns:
        The output as a string, or None if the command failed.
    """
    try:
        return subprocess.check_output(args)
    except subprocess.CalledProcessError:
        return None


def collect_dynamic_libs(*search_paths):
    """Collects a list of dynamic libraries.

    Args:
        *search_paths: String, paths to search in

    Returns:
        Dictionary, mapping library names to their respective paths.
    """
    dylibs = {}
    for search_path in search_paths:
        output = execute('find', search_path, '-name', '*.dylib')
        if output:
            for filename in output.split():
                if filename.endswith('.dylib'):
                    dylibs[libname(filename)] = filename
    return dylibs


def get_links(paths):
    """Get shared library links using otool.

    Args:
        paths: Iterable (strings), paths to get links for

    Returns:
        Dictionary, mapping the path to the list of links it has
    """
    links = {}
    output = execute('otool', '-L', *paths)
    if output:
        output_iter = iter(output.split('\n'))
        try:
            current_path = None
            while True:
                line = next(output_iter)
                if line:
                    if line[0].isspace():
                        if current_path is None:
                            continue  # you makin' me a sad
                        link = line.strip().partition(' ')[0]
                        links.setdefault(current_path, []).append(link)
                    else:
                        # Trim the colon at the end
                        current_path = line.strip()[:-1]
        except StopIteration:
            pass
    return links


def fix_links(paths, search_paths=None):
    """Fix broken shared library links in a file.

    Args:
        paths: Iterable (strings), paths to files to attempt to fix
        search_paths: Iterable (strings, optional), optional set of search
            paths to use when looking for replacement paths
    """
    search_paths = list(search_paths or [])
    search_paths.extend((
        '/usr/lib',
        '/usr/local/lib',
        '/usr/local/opt/lib',
        '/usr/local/Cellar',
    ))

    # Collect dynamic library locations
    search_paths = set(filter(os.path.exists, search_paths))
    dylibs = collect_dynamic_libs(*search_paths)

    # install_name_tool doesn't play nice with symbolic links, so resolve them
    paths = set(map(os.path.realpath, paths))

    # Find shared library links in binaries
    path_links = get_links(filter(os.path.exists, paths))

    # See if any of them are broken, and fix them if so
    for path, links in path_links.iteritems():
        changes = []
        for link in filter(lambda s: s.startswith('/'), links):
            if not os.path.exists(link):
                link_libname = libname(link)
                new_link = dylibs.get(link_libname)
                changes.append((link, new_link))
        if changes:
            print 'Fixing broken links in', path
            for old_link, new_link in changes:
                if new_link:
                    print '    ', old_link, '-->', new_link
                    execute('install_name_tool', '-change', old_link, new_link,
                            path)
                else:
                    print '    ', 'No lib found for', old_link


if __name__ == '__main__':
    desc, epilog = __doc__.split('\n', 1)
    parser = argparse.ArgumentParser(
        description=desc, epilog=epilog,
        formatter_class=argparse.RawDescriptionHelpFormatter)
    parser.add_argument(
        'paths', nargs='+',
        help='paths to binaries with broken shared library links')
    parser.add_argument(
        '--search_paths', action='append',
        help='additional search paths when looking for replacement libs')

    # TODO: option to specify a library name and specific version to change
    #       to use when changing links

    args = parser.parse_args()
    fix_links(args.paths, search_paths=args.search_paths)