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

2002年8月08日 19:14:37 -0700

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;