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, 7 insertions, 0 deletions

diff --git a/Misc/NEWS.d/next/Core and Builtins/2021-02-18-15-12-30.bpo-42990.toAqBH.rst b/Misc/NEWS.d/next/Core and Builtins/2021-02-18-15-12-30.bpo-42990.toAqBH.rst
new file mode 100644
index 0000000..b9e6647
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2021-02-18-15-12-30.bpo-42990.toAqBH.rst
@@ -0,0 +1,7 @@
+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.
+Patch by Victor Stinner.