[Python-checkins] cpython: Optimize _PyFunction_FastCallDict() when kwargs is {}

[victor.stinner]

https://hg.python.org/cpython/rev/f9dd607dc04c
changeset:   105973:f9dd607dc04c
user:        Victor Stinner <victor.stinner at gmail.com>
date:        Tue Jan 03 02:01:42 2017 +0100
summary:
  Optimize _PyFunction_FastCallDict() when kwargs is {}

Issue #28839: Optimize _PyFunction_FastCallDict() when kwargs is an empty
dictionary, avoid the creation of an useless empty tuple.

files:
  Python/ceval.c |  8 +++++---
  1 files changed, 5 insertions(+), 3 deletions(-)


diff --git a/Python/ceval.c b/Python/ceval.c
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -5040,9 +5040,9 @@
         }
     }
 
-    if (kwargs != NULL) {
+    nk = (kwargs != NULL) ? PyDict_GET_SIZE(kwargs) : 0;
+    if (nk != 0) {
         Py_ssize_t pos, i;
-        nk = PyDict_GET_SIZE(kwargs);
 
         kwtuple = PyTuple_New(2 * nk);
         if (kwtuple == NULL) {
@@ -5052,6 +5052,9 @@
         k = &PyTuple_GET_ITEM(kwtuple, 0);
         pos = i = 0;
         while (PyDict_Next(kwargs, &pos, &k[i], &k[i+1])) {
+            /* We must hold strong references because keyword arguments can be
+               indirectly modified while the function is called:
+               see issue #2016 and test_extcall */
             Py_INCREF(k[i]);
             Py_INCREF(k[i+1]);
             i += 2;
@@ -5061,7 +5064,6 @@
     else {
         kwtuple = NULL;
         k = NULL;
-        nk = 0;
     }
 
     kwdefs = PyFunction_GET_KW_DEFAULTS(func);

-- 
Repository URL: https://hg.python.org/cpython