Add tools/mac/show_mod_init_func.py to symbolize static initializers without a dSYM.

tools/mac/show_mod_init_func.py

+#!/usr/bin/env python
+
+# Copyright 2016 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.
+
+"""
+Prints the contents of the __DATA,__mod_init_func section of a Mach-O image.
+
+Usage:
+  tools/mac/show_mod_init_func.py out/gn/Chromium\ Framework.unstripped
+
+This is meant to be used on a Mach-O executable. If a dSYM is present, use
+dump-static-initializers.py instead.
+"""
+
+import optparse
+import subprocess
+import sys
+
+
+def ShowModuleInitializers(binary):
+  """Gathers the module initializers for |binary| and symbolizes the addresses.
+  """
+  initializers = GetModuleInitializers(binary)
+  if not initializers:
+    # atos will do work even if there are no addresses, so bail early.
+    return
+  symbols = SymbolizeAddresses(binary, initializers)
+
+  print binary
+  for initializer in zip(initializers, symbols):
+    print '%s @ %s' % initializer
+
+
+def GetModuleInitializers(binary):
+  """Parses the __DATA,__mod_init_func segment of |binary| and returns a list
+  of string hexadecimal addresses of the module initializers.
+  """
+  # The -v flag will display the addresses in a usable form (as opposed to
+  # just its on-disk little-endian byte representation).
+  otool = ['otool', '-v', '-s', '__DATA', '__mod_init_func', binary]
+  lines = subprocess.check_output(otool).strip().split('\n')
+
+  # Skip the first two header lines and then get the address of the
+  # initializer in the second column. The first address is the address
+  # of the initializer pointer.
+  #   out/gn/Chromium Framework.unstripped:
+  #   Contents of (__DATA,__mod_init_func) section
+  #   0x0000000008761498 0x000000000385d120
+  return [line.split(' ')[1] for line in lines[2:]]
+
+
+def SymbolizeAddresses(binary, addresses):
+  """Given a |binary| and a list of |addresses|, symbolizes them using atos.
+  """
+  atos = ['atos', '-o', binary] + addresses
+  lines = subprocess.check_output(atos).strip().split('\n')
+  return lines
+
+
+def Main():
+  parser = optparse.OptionParser(usage='%prog filename')
+  opts, args = parser.parse_args()
+  if len(args) != 1:
+    parser.error('missing binary filename')
+    return 1
+
+  ShowModuleInitializers(args[0])
+  return 0
+
+if __name__ == '__main__':
+  sys.exit(Main())