Beginning work on GN build

build/toolchain/gcc_solink_wrapper.py

+#!/usr/bin/env python
+# Copyright 2015 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.
+
+"""Runs 'ld -shared' and generates a .TOC file that's untouched when unchanged.
+
+This script exists to avoid using complex shell commands in
+gcc_toolchain.gni's tool("solink"), in case the host running the compiler
+does not have a POSIX-like shell (e.g. Windows).
+"""
+
+import argparse
+import os
+import re
+import subprocess
+import sys
+
+
+# When running on a Windows host and using a toolchain whose tools are
+# actually wrapper scripts (i.e. .bat files on Windows) rather than binary
+# executables, the "command" to run has to be prefixed with this magic.
+# The GN toolchain definitions take care of that for when GN/Ninja is
+# running the tool directly.  When that command is passed in to this
+# script, it appears as a unitary string but needs to be split up so that
+# just 'cmd' is the actual command given to Python's subprocess module.
+BAT_PREFIX = 'cmd /c call '
+
+def CommandToRun(command):
+  if command[0].startswith(BAT_PREFIX):
+    command = command[0].split(None, 3) + command[1:]
+  return command
+
+
+def CollectSONAME(args):
+  """Replaces: readelf -d $sofile | grep SONAME"""
+  toc = ''
+  readelf = subprocess.Popen(CommandToRun([args.readelf, '-d', args.sofile]),
+                             stdout=subprocess.PIPE, bufsize=-1)
+  for line in readelf.stdout:
+    if 'SONAME' in line:
+      toc += line
+  return readelf.wait(), toc
+
+
+def CollectDynSym(args):
+  """Replaces: nm --format=posix -g -D $sofile | cut -f1-2 -d' '"""
+  toc = ''
+  nm = subprocess.Popen(CommandToRun([
+      args.nm, '--format=posix', '-g', '-D', args.sofile]),
+                        stdout=subprocess.PIPE, bufsize=-1)
+  for line in nm.stdout:
+    toc += ' '.join(line.split(' ', 2)[:2]) + '\n'
+  return nm.wait(), toc
+
+
+def CollectTOC(args):
+  result, toc = CollectSONAME(args)
+  if result == 0:
+    result, dynsym = CollectDynSym(args)
+    toc += dynsym
+  return result, toc
+
+
+def UpdateTOC(tocfile, toc):
+  if os.path.exists(tocfile):
+    old_toc = open(tocfile, 'r').read()
+  else:
+    old_toc = None
+  if toc != old_toc:
+    open(tocfile, 'w').write(toc)
+
+
+def main():
+  parser = argparse.ArgumentParser(description=__doc__)
+  parser.add_argument('--readelf',
+                      required=True,
+                      help='The readelf binary to run',
+                      metavar='PATH')
+  parser.add_argument('--nm',
+                      required=True,
+                      help='The nm binary to run',
+                      metavar='PATH')
+  parser.add_argument('--strip',
+                      help='The strip binary to run',
+                      metavar='PATH')
+  parser.add_argument('--sofile',
+                      required=True,
+                      help='Shared object file produced by linking command',
+                      metavar='FILE')
+  parser.add_argument('--tocfile',
+                      required=True,
+                      help='Output table-of-contents file',
+                      metavar='FILE')
+  parser.add_argument('--output',
+                      required=True,
+                      help='Final output shared object file',
+                      metavar='FILE')
+  parser.add_argument('command', nargs='+',
+                      help='Linking command')
+  args = parser.parse_args()
+
+  # First, run the actual link.
+  result = subprocess.call(CommandToRun(args.command))
+  if result != 0:
+    return result
+
+  # Next, generate the contents of the TOC file.
+  result, toc = CollectTOC(args)
+  if result != 0:
+    return result
+
+  # If there is an existing TOC file with identical contents, leave it alone.
+  # Otherwise, write out the TOC file.
+  UpdateTOC(args.tocfile, toc)
+
+  # Finally, strip the linked shared object file (if desired).
+  if args.strip:
+    result = subprocess.call(CommandToRun([args.strip, '--strip-unneeded',
+                                           '-o', args.output, args.sofile]))
+
+  return result
+
+
+if __name__ == "__main__":
+  sys.exit(main())