gecko-dev/build/autoconf/libstdcxx.py

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Python
Executable File

#!/usr/bin/python
# This Source Code Form is subject to the terms of the Mozilla Public
# License, v. 2.0. If a copy of the MPL was not distributed with this
# file, You can obtain one at http://mozilla.org/MPL/2.0/.
# This script find the version of libstdc++ and prints it as single number
# with 8 bits per element. For example, GLIBCXX_3.4.10 becomes
# 3 << 16 | 4 << 8 | 10 = 197642. This format is easy to use
# in the C preprocessor.
# We find out both the host and target versions. Since the output
# will be used from shell, we just print the two assignments and evaluate
# them from shell.
import os
import subprocess
import re
re_for_ld = re.compile('.*\((.*)\).*')
def parse_readelf_line(x):
"""Return the version from a readelf line that looks like:
0x00ec: Rev: 1 Flags: none Index: 8 Cnt: 2 Name: GLIBCXX_3.4.6
"""
return x.split(':')[-1].split('_')[-1].strip()
def parse_ld_line(x):
"""Parse a line from the output of ld -t. The output of gold is just
the full path, gnu ld prints "-lstdc++ (path)".
"""
t = re_for_ld.match(x)
if t:
return t.groups()[0].strip()
return x.strip()
def split_ver(v):
"""Covert the string '1.2.3' into the list [1,2,3]
"""
return [int(x) for x in v.split('.')]
def cmp_ver(a, b):
"""Compare versions in the form 'a.b.c'
"""
for (i, j) in zip(split_ver(a), split_ver(b)):
if i != j:
return i - j
return 0
def encode_ver(v):
"""Encode the version as a single number.
"""
t = split_ver(v)
return t[0] << 16 | t[1] << 8 | t[2]
def find_version(e):
"""Given the value of environment variable CXX or HOST_CXX, find the
version of the libstdc++ it uses.
"""
args = e.split()
args += ['-shared', '-Wl,-t']
p = subprocess.Popen(args, stderr=subprocess.STDOUT, stdout=subprocess.PIPE)
candidates = [x for x in p.stdout if 'libstdc++.so' in x]
assert len(candidates) == 1
libstdcxx = parse_ld_line(candidates[-1])
p = subprocess.Popen(['readelf', '-V', libstdcxx], stdout=subprocess.PIPE)
versions = [parse_readelf_line(x)
for x in p.stdout.readlines() if 'Name: GLIBCXX' in x]
last_version = sorted(versions, cmp = cmp_ver)[-1]
return encode_ver(last_version)
if __name__ == '__main__':
cxx_env = os.environ['CXX']
print 'MOZ_LIBSTDCXX_TARGET_VERSION=%s' % find_version(cxx_env)
host_cxx_env = os.environ.get('HOST_CXX', cxx_env)
print 'MOZ_LIBSTDCXX_HOST_VERSION=%s' % find_version(host_cxx_env)