gcc_solink_wrapper.py revision 342c50ce1624b485728b9a4fc41d8bbf37eb46cf 
1#!/usr/bin/env python
2# Copyright 2015 The Chromium Authors. All rights reserved.
3# Use of this source code is governed by a BSD-style license that can be
4# found in the LICENSE file.
5
6"""Runs 'ld -shared' and generates a .TOC file that's untouched when unchanged.
7
8This script exists to avoid using complex shell commands in
9gcc_toolchain.gni's tool("solink"), in case the host running the compiler
10does not have a POSIX-like shell (e.g. Windows).
11"""
12
13import argparse
14import os
15import re
16import subprocess
17import sys
18
19
20# When running on a Windows host and using a toolchain whose tools are
21# actually wrapper scripts (i.e. .bat files on Windows) rather than binary
22# executables, the "command" to run has to be prefixed with this magic.
23# The GN toolchain definitions take care of that for when GN/Ninja is
24# running the tool directly.  When that command is passed in to this
25# script, it appears as a unitary string but needs to be split up so that
26# just 'cmd' is the actual command given to Python's subprocess module.
27BAT_PREFIX = 'cmd /c call '
28
29def CommandToRun(command):
30  if command[0].startswith(BAT_PREFIX):
31    command = command[0].split(None, 3) + command[1:]
32  return command
33
34
35def CollectSONAME(args):
36  """Replaces: readelf -d $sofile | grep SONAME"""
37  toc = ''
38  readelf = subprocess.Popen(CommandToRun([args.readelf, '-d', args.sofile]),
39                             stdout=subprocess.PIPE, bufsize=-1)
40  for line in readelf.stdout:
41    if 'SONAME' in line:
42      toc += line
43  return readelf.wait(), toc
44
45
46def CollectDynSym(args):
47  """Replaces: nm --format=posix -g -D $sofile | cut -f1-2 -d' '"""
48  toc = ''
49  nm = subprocess.Popen(CommandToRun([
50      args.nm, '--format=posix', '-g', '-D', args.sofile]),
51                        stdout=subprocess.PIPE, bufsize=-1)
52  for line in nm.stdout:
53    toc += ' '.join(line.split(' ', 2)[:2]) + '\n'
54  return nm.wait(), toc
55
56
57def CollectTOC(args):
58  result, toc = CollectSONAME(args)
59  if result == 0:
60    result, dynsym = CollectDynSym(args)
61    toc += dynsym
62  return result, toc
63
64
65def UpdateTOC(tocfile, toc):
66  if os.path.exists(tocfile):
67    old_toc = open(tocfile, 'r').read()
68  else:
69    old_toc = None
70  if toc != old_toc:
71    open(tocfile, 'w').write(toc)
72
73
74def main():
75  parser = argparse.ArgumentParser(description=__doc__)
76  parser.add_argument('--readelf',
77                      required=True,
78                      help='The readelf binary to run',
79                      metavar='PATH')
80  parser.add_argument('--nm',
81                      required=True,
82                      help='The nm binary to run',
83                      metavar='PATH')
84  parser.add_argument('--strip',
85                      help='The strip binary to run',
86                      metavar='PATH')
87  parser.add_argument('--sofile',
88                      required=True,
89                      help='Shared object file produced by linking command',
90                      metavar='FILE')
91  parser.add_argument('--tocfile',
92                      required=True,
93                      help='Output table-of-contents file',
94                      metavar='FILE')
95  parser.add_argument('--output',
96                      required=True,
97                      help='Final output shared object file',
98                      metavar='FILE')
99  parser.add_argument('command', nargs='+',
100                      help='Linking command')
101  args = parser.parse_args()
102
103  # First, run the actual link.
104  result = subprocess.call(CommandToRun(args.command))
105  if result != 0:
106    return result
107
108  # Next, generate the contents of the TOC file.
109  result, toc = CollectTOC(args)
110  if result != 0:
111    return result
112
113  # If there is an existing TOC file with identical contents, leave it alone.
114  # Otherwise, write out the TOC file.
115  UpdateTOC(args.tocfile, toc)
116
117  # Finally, strip the linked shared object file (if desired).
118  if args.strip:
119    result = subprocess.call(CommandToRun([args.strip, '--strip-unneeded',
120                                           '-o', args.output, args.sofile]))
121
122  return result
123
124
125if __name__ == "__main__":
126  sys.exit(main())
127