[BinarySize] Filter duplicate lines in nm output.

tools/binary_size/binary_size_utils.py

 # Copyright 2014 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.
 
 """Common utilities for tools that deal with binary size information.
 """
 
 import logging
 import re
 
@@ skipping 17 matching lines @@
                       '(.) ' # symbol type, one character
                       '([^\t]+)' # symbol name, separated from next by tab
                       '(?:\t(.*):[\d\?]+)?.*$') # location
   # Match lines with addr but no size.
   addr_re = re.compile(r'^[0-9a-f]{8,} (.) ([^\t]+)(?:\t.*)?$')
   # Match lines that don't have an address at all -- typically external symbols.
   noaddr_re = re.compile(r'^ {8,} (.) (.*)$')
   # Match lines with no symbol name, only addr and type
   addr_only_re = re.compile(r'^[0-9a-f]{8,} (.)$')
 
+  seen_lines = set()
   for line in nm_lines:
     line = line.rstrip()
+    if line in seen_lines:
+      # nm outputs identical lines at times. We don't want to treat
+      # those as distinct symbols because that would make no sense.
+      continue
+    seen_lines.add(line)
     match = sym_re.match(line)
     if match:
       address, size, sym_type, sym = match.groups()[0:4]
       size = int(size, 16)
       if sym_type in ('B', 'b'):
         continue  # skip all BSS for now.
       path = match.group(5)
       yield sym, sym_type, size, path, address
       continue
     match = addr_re.match(line)
     if match:
       # sym_type, sym = match.groups()[0:2]
       continue  # No size == we don't care.
     match = noaddr_re.match(line)
     if match:
       sym_type, sym = match.groups()
       if sym_type in ('U', 'w'):
         continue  # external or weak symbol
     match = addr_only_re.match(line)
     if match:
       continue  # Nothing to do.
 
 
     # If we reach this part of the loop, there was something in the
     # line that we didn't expect or recognize.
     logging.warning('nm output parser failed to parse: %s', repr(line))