GN: Avoid nontrivial shell commands in gcc_toolchain tools

build/toolchain/gcc_solink_wrapper.py

Index: build/toolchain/gcc_solink_wrapper.py
diff --git a/build/toolchain/gcc_solink_wrapper.py b/build/toolchain/gcc_solink_wrapper.py
new file mode 100755
index 0000000000000000000000000000000000000000..59533d27b8dd33f782d517bf8df82bf1124bd145
--- /dev/null
+++ b/build/toolchain/gcc_solink_wrapper.py
@@ -0,0 +1,107 @@
+#!/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
+
+def CollectSONAME(args):
+  """Replaces: readelf -d $sofile | grep SONAME
+  """

[Dirk Pranke, 2015/10/28 22:13:03]

nit: format the comments on a single line here.

[Roland McGrath, 2015/10/28 22:25:16]

Done.

+  toc = ''
+  soname_re = re.compile('SONAME')
+  readelf = subprocess.Popen([args.readelf, '-d', args.sofile],
+                             stdout=subprocess.PIPE, bufsize=-1)
+  for line in readelf.stdout:
+    if soname_re.search(line):

[Dirk Pranke, 2015/10/28 22:13:03]

nit: you could skip the re here and just do:

  if 'SONAME' in line:
    toc += line

I'd probably also do:

  stdout, _ = readelf.communicate()
  for line in stdout:
    ...
  return readelf.returncode, toc

instead, but it's roughly equivalent.

[Roland McGrath, 2015/10/28 22:25:16]

Done.

+      toc += line
+  return readelf.wait(), toc
+

[Dirk Pranke, 2015/10/28 22:13:03]

nit two blank lines between top-level functions.

[Roland McGrath, 2015/10/28 22:25:16]

Done.

+def CollectDynSym(args):
+  """Replaces: nm --format=posix -g -D $sofile | cut -f1-2 -d

[Dirk Pranke, 2015/10/28 22:13:03]

nit: cut -f1-2 -d' '

[Roland McGrath, 2015/10/28 22:25:16]

Done.

+  """
+  toc = ''
+  nm = subprocess.Popen([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(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([args.strip, '--strip-unneeded',
+                              '-o', args.output, args.sofile])
+
+  return result
+
+if __name__ == "__main__":
+  sys.exit(main())