[Python-checkins] cpython (merge 3.3 -> default): merge 3.3 (#6627)

[benjamin.peterson]

http://hg.python.org/cpython/rev/fd647825475a
changeset:   88577:fd647825475a
parent:      88572:d0e2437136f5
parent:      88574:a6f748f40da6
user:        Benjamin Peterson <benjamin at python.org>
date:        Mon Jan 20 00:12:24 2014 -0500
summary:
  merge 3.3 (#6627)

files:
  Doc/library/ctypes.rst |  18 ++++++++++++------
  1 files changed, 12 insertions(+), 6 deletions(-)


diff --git a/Doc/library/ctypes.rst b/Doc/library/ctypes.rst
--- a/Doc/library/ctypes.rst
+++ b/Doc/library/ctypes.rst
@@ -1022,12 +1022,18 @@
    1 5 7 33 99
    >>>
 
-**Important note for callback functions:**
-
-Make sure you keep references to :func:`CFUNCTYPE` objects as long as they are
-used from C code. :mod:`ctypes` doesn't, and if you don't, they may be garbage
-collected, crashing your program when a callback is made.
-
+.. note::
+
+   Make sure you keep references to :func:`CFUNCTYPE` objects as long as they
+   are used from C code. :mod:`ctypes` doesn't, and if you don't, they may be
+   garbage collected, crashing your program when a callback is made.
+
+   Also, note that if the callback function is called in a thread created
+   outside of Python's control (e.g. by the foreign code that calls the
+   callback), ctypes creates a new dummy Python thread on every invocation. This
+   behavior is correct for most purposes, but it means that values stored with
+   `threading.local` will *not* survive across different callbacks, even when
+   those calls are made from the same C thread.
 
 .. _ctypes-accessing-values-exported-from-dlls:
 

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