Down-integrate from google internal.

1 files changed, 27 insertions, 1 deletions

diff --git a/python/google/protobuf/symbol_database.py b/python/google/protobuf/symbol_database.py
index 4c70b393..b81ef4d7 100644
--- a/python/google/protobuf/symbol_database.py
+++ b/python/google/protobuf/symbol_database.py
@@ -60,6 +60,7 @@ Example usage:
 """
 
 
+from google.protobuf import descriptor as _descriptor
 from google.protobuf import descriptor_pool
 
 
@@ -72,6 +73,31 @@ class SymbolDatabase(object):
   buffer types used within a program.
   """
 
+  # pylint: disable=protected-access
+  if _descriptor._USE_C_DESCRIPTORS:
+
+    def __new__(cls):
+      raise TypeError("Instances of SymbolDatabase cannot be created")
+
+    @classmethod
+    def _CreateDefaultDatabase(cls):
+      self = object.__new__(cls)  # Bypass the __new__ above.
+      # Don't call __init__() and initialize here.
+      self._symbols = {}
+      self._symbols_by_file = {}
+      # As of today all descriptors are registered and retrieved from
+      # _message.default_pool (see FileDescriptor.__new__), so it's not
+      # necessary to use another pool.
+      self.pool = _descriptor._message.default_pool
+      return self
+  # pylint: enable=protected-access
+
+  else:
+
+    @classmethod
+    def _CreateDefaultDatabase(cls):
+      return cls()
+
   def __init__(self):
     """Constructor."""
 
@@ -177,7 +203,7 @@ class SymbolDatabase(object):
       result.update(self._symbols_by_file[f])
     return result
 
-_DEFAULT = SymbolDatabase()
+_DEFAULT = SymbolDatabase._CreateDefaultDatabase()
 
 
 def Default():