find_incompatible_glibc_symbols.py

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#!/usr/bin/env python

# Copyright 2018 The Chromium Authors. All rights reserved.

# Use of this source code is governed by a BSD-style license that can be

# found in the LICENSE file.

"""Find incompatible symbols in glibc and output a list of replacements.

"""

from __future__ import print_function

import re

import sys

# This constant comes from https://crbug.com/580892

MAX_ALLOWED_GLIBC_VERSION = [2, 17]

def get_replacements(nm_file, max_allowed_glibc_version):

  version_format = re.compile('GLIBC_[0-9\.]+')

  symbols = {}

  for line in nm_file:

    # Some versions of nm have a bug where the version gets printed twice.

    # Since the symbol may either be formatted like "name@@VERSION" or

    # "name@@VERSION@@VERSION", handle both cases.

    line = line.replace('@@', '@')

    symver = line.split('@')

    symbol = symver[0].split(' ')[-1]

    version = symver[-1]

    if not re.match(version_format, version):

      continue

    if symbol in symbols:

      symbols[symbol].add(version)

    else:

      symbols[symbol] = set([version])

  replacements = []

  for symbol, versions in symbols.items():

    if len(versions) <= 1:

      continue

    versions_parsed = [[

        int(part) for part in version.lstrip('GLIBC_').split('.')

    ] for version in versions]

    if (max(versions_parsed) > max_allowed_glibc_version and

        min(versions_parsed) <= max_allowed_glibc_version):

      # Use the newest allowed version of the symbol.

      replacement_version_parsed = max([

          version for version in versions_parsed

          if version <= max_allowed_glibc_version

])

      replacement_version = 'GLIBC_' + '.'.join(

          [str(part) for part in replacement_version_parsed])

      replacements.append('__asm__(".symver %s, %s@%s");' %

                          (symbol, symbol, replacement_version))

  return sorted(replacements)

if __name__ == '__main__':

  replacements = get_replacements(sys.stdin, MAX_ALLOWED_GLIBC_VERSION)

  if replacements:

    print('// Chromium-specific hack.')

    print('// See explanation in sysroot-creator.sh.')

    for replacement in replacements:

      print(replacement)