bpo-42990: Functions inherit current builtins (GH-24564)

The types.FunctionType constructor now inherits the current builtins
if the globals dictionary has no "__builtins__" key, rather than
using {"None": None} as builtins: same behavior as eval() and exec()
functions.

Defining a function with "def function(...): ..." in Python is not
affected, globals cannot be overriden with this syntax: it also
inherits the current builtins.

PyFrame_New(), PyEval_EvalCode(), PyEval_EvalCodeEx(),
PyFunction_New() and PyFunction_NewWithQualName() now inherits the
current builtins namespace if the globals dictionary has no
"__builtins__" key.

* Add _PyEval_GetBuiltins() function.
* _PyEval_BuiltinsFromGlobals() now uses _PyEval_GetBuiltins() if
  builtins cannot be found in globals.
* Add tstate parameter to _PyEval_BuiltinsFromGlobals().

1 files changed, 10 insertions, 1 deletions

diff --git a/Doc/whatsnew/3.10.rst b/Doc/whatsnew/3.10.rst
index c4a79b6..2ceb26f 100644
--- a/Doc/whatsnew/3.10.rst
+++ b/Doc/whatsnew/3.10.rst
@@ -282,7 +282,8 @@ Other Language Changes
 
 * Functions have a new ``__builtins__`` attribute which is used to look for
   builtin symbols when a function is executed, instead of looking into
-  ``__globals__['__builtins__']``.
+  ``__globals__['__builtins__']``. The attribute is initialized from
+  ``__globals__["__builtins__"]`` if it exists, else from the current builtins.
   (Contributed by Mark Shannon in :issue:`42990`.)
 
 
@@ -789,6 +790,14 @@ Changes in the Python API
   (Contributed by Yurii Karabas, Andrew Svetlov, Yury Selivanov and Kyle Stanley
   in :issue:`42392`.)
 
+* The :data:`types.FunctionType` constructor now inherits the current builtins
+  if the *globals* dictionary has no ``"__builtins__"`` key, rather than using
+  ``{"None": None}`` as builtins: same behavior as :func:`eval` and
+  :func:`exec` functions.  Defining a function with ``def function(...): ...``
+  in Python is not affected, globals cannot be overriden with this syntax: it
+  also inherits the current builtins.
+  (Contributed by Victor Stinner in :issue:`42990`.)
+
 CPython bytecode changes
 ========================