utils/check_cfc/obj_diff.py

   1 #!/usr/bin/env python2.7
   2
   3 from __future__ import print_function
   4
   5 import argparse
   6 import difflib
   7 import os
   8 import subprocess
   9 import sys
  10
  11 disassembler = 'objdump'
  12
  13 def keep_line(line):
  14     """Returns true for lines that should be compared in the disassembly
  15     output."""
  16     return "file format" not in line
  17
  18 def disassemble(objfile):
  19     """Disassemble object to a file."""
  20     p = subprocess.Popen([disassembler, '-d', objfile],
  21                          stdout=subprocess.PIPE,
  22                          stderr=subprocess.PIPE)
  23     (out, err) = p.communicate()
  24     if p.returncode or err:
  25         print("Disassemble failed: {}".format(objfile))
  26         sys.exit(1)
  27     return filter(keep_line, out.split(os.linesep))
  28
  29 def first_diff(a, b, fromfile, tofile):
  30     """Returns the first few lines of a difference, if there is one.  Python
  31     diff can be very slow with large objects and the most interesting changes
  32     are the first ones. Truncate data before sending to difflib.  Returns None
  33     is there is no difference."""
  34
  35     # Find first diff
  36     first_diff_idx = None
  37     for idx, val in enumerate(a):
  38         if val != b[idx]:
  39             first_diff_idx = idx
  40             break
  41
  42     if first_diff_idx == None:
  43         # No difference
  44         return None
  45
  46     # Diff to first line of diff plus some lines
  47     context = 3
  48     diff = difflib.unified_diff(a[:first_diff_idx+context],
  49                                 b[:first_diff_idx+context],
  50                                 fromfile,
  51                                 tofile)
  52     difference = "\n".join(diff)
  53     if first_diff_idx + context < len(a):
  54         difference += "\n*** Diff truncated ***"
  55     return difference
  56
  57 def compare_object_files(objfilea, objfileb):
  58     """Compare disassembly of two different files.
  59        Allowing unavoidable differences, such as filenames.
  60        Return the first difference if the disassembly differs, or None.
  61     """
  62     disa = disassemble(objfilea)
  63     disb = disassemble(objfileb)
  64     return first_diff(disa, disb, objfilea, objfileb)
  65
  66 if __name__ == '__main__':
  67     parser = argparse.ArgumentParser()
  68     parser.add_argument('objfilea', nargs=1)
  69     parser.add_argument('objfileb', nargs=1)
  70     parser.add_argument('-v', '--verbose', action='store_true')
  71     args = parser.parse_args()
  72     diff = compare_object_files(args.objfilea[0], args.objfileb[0])
  73     if diff:
  74         print("Difference detected")
  75         if args.verbose:
  76             print(diff)
  77         sys.exit(1)
  78     else:
  79         print("The same")