[Python-checkins] python/dist/src/Objects typeobject.c,2.169,2.170

[gvanrossum@users.sourceforge.net]

Update of /cvsroot/python/python/dist/src/Objects
In directory usw-pr-cvs1:/tmp/cvs-serv7602

Modified Files:
	typeobject.c 
Log Message:
Major speedup for new-style class creation.  Turns out there was some
trampolining going on with the tp_new descriptor, where the inherited
PyType_GenericNew was overwritten with the much slower slot_tp_new
which would end up calling tp_new_wrapper which would eventually call
PyType_GenericNew.  Add a special case for this to update_one_slot().

XXX Hope there isn't a loophole in this.  I'll buy the first person to
point out a bug in the reasoning a beer.

Backport candidate (but I won't do it).


Index: typeobject.c
===================================================================
RCS file: /cvsroot/python/python/dist/src/Objects/typeobject.c,v
retrieving revision 2.169
retrieving revision 2.170
diff -C2 -d -r2.169 -r2.170
*** typeobject.c	8 Aug 2002 21:57:53 -0000	2.169
--- typeobject.c	9 Aug 2002 02:14:34 -0000	2.170
***************
*** 4082,4085 ****
--- 4082,4107 ----
  			}
  		}
+ 		else if (descr->ob_type == &PyCFunction_Type &&
+ 			 PyCFunction_GET_FUNCTION(descr) ==
+ 			 (PyCFunction)tp_new_wrapper &&
+ 			 strcmp(p->name, "__new__") == 0)
+ 		{
+ 			/* The __new__ wrapper is not a wrapper descriptor,
+ 			   so must be special-cased differently.
+ 			   If we don't do this, creating an instance will
+ 			   always use slot_tp_new which will look up
+ 			   __new__ in the MRO which will call tp_new_wrapper
+ 			   which will look through the base classes looking
+ 			   for a static base and call its tp_new (usually
+ 			   PyType_GenericNew), after performing various
+ 			   sanity checks and constructing a new argument
+ 			   list.  Cut all that nonsense short -- this speeds
+ 			   up instance creation tremendously. */
+ 			specific = type->tp_new;
+ 			/* XXX I'm not 100% sure that there isn't a hole
+ 			   in this reasoning that requires additional
+ 			   sanity checks.  I'll buy the first person to
+ 			   point out a bug in this reasoning a beer. */
+ 		}
  		else {
  			use_generic = 1;