supersize: Track symbol aliases and shared symbols

tools/binary_size/libsupersize/file_format.py

Index: tools/binary_size/libsupersize/file_format.py
diff --git a/tools/binary_size/libsupersize/file_format.py b/tools/binary_size/libsupersize/file_format.py
index 537523a8a3834f135aded908c96339df086c6eb5..867d29c5e063030a817baa5eabe231381ff8286a 100644
--- a/tools/binary_size/libsupersize/file_format.py
+++ b/tools/binary_size/libsupersize/file_format.py
@@ -80,10 +80,14 @@ def _SaveSizeInfoToFile(size_info, file_obj):
                 delta=True)
   _LogSize(file_obj, 'path indices')  # For libchrome: adds 125kb.
 
+  prev_aliases = None
   for group in by_section:
     for symbol in group:
       # Do not write name when full_name exists. It will be derived on load.
       file_obj.write(symbol.full_name or symbol.name)
+      if symbol.aliases and symbol.aliases is not prev_aliases:
+        file_obj.write('\t0%x' % symbol.num_aliases)
+      prev_aliases = symbol.aliases
       if symbol.flags:
         file_obj.write('\t%x' % symbol.flags)
       file_obj.write('\n')
@@ -132,14 +136,24 @@ def _LoadSizeInfoFromFile(file_obj):
   raw_symbols = [None] * sum(section_counts)
   symbol_idx = 0
   for section_index, cur_section_name in enumerate(section_names):
+    alias_counter = 0
     for i in xrange(section_counts[section_index]):
-      line = next(lines)[:-1]
-      name = line
-      flags = 0
-      last_tab_idx = line.find('\t', -3)  # Allows for two digits of flags.
-      if last_tab_idx != -1:
-        flags = int(line[last_tab_idx + 1:], 16)
-        name = line[:last_tab_idx]
+      parts = next(lines)[:-1].split('\t')
+      flags_part = None
+      aliases_part = None
+
+      if len(parts) == 3:
+        aliases_part = parts[1]
+        flags_part = parts[2]
+      elif len(parts) == 2:
+        if parts[1][0] == '0':
+          aliases_part = parts[1]
+        else:
+          flags_part = parts[1]
+
+      name = parts[0]
+      flags = int(flags_part, 16) if flags_part else 0
+      num_aliases = int(aliases_part, 16) if aliases_part else 0
 
       new_sym = models.Symbol.__new__(models.Symbol)
       new_sym.section_name = cur_section_name
@@ -152,6 +166,18 @@ def _LoadSizeInfoFromFile(file_obj):
       new_sym.flags = flags
       new_sym.padding = 0  # Derived
       new_sym.full_name = None  # Derived
+
+      if num_aliases:
+        assert alias_counter == 0
+        new_sym.aliases = [new_sym]
+        alias_counter = num_aliases - 1
+      elif alias_counter > 0:
+        new_sym.aliases = raw_symbols[symbol_idx - 1].aliases
+        new_sym.aliases.append(new_sym)
+        alias_counter -= 1
+      else:
+        new_sym.aliases = None
+
       raw_symbols[symbol_idx] = new_sym
       symbol_idx += 1
 
@@ -160,7 +186,7 @@ def _LoadSizeInfoFromFile(file_obj):
 
 def SaveSizeInfo(size_info, path):
   """Saves |size_info| to |path}."""
-  if os.environ.get('MEASURE_GZIP') == '1':
+  if os.environ.get('SUPERSIZE_MEASURE_GZIP') == '1':
     with gzip.open(path, 'wb') as f:
       _SaveSizeInfoToFile(size_info, f)
   else: