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, 6 insertions, 2 deletions

diff --git a/Objects/funcobject.c b/Objects/funcobject.c
index 4b92f6c..36df88a 100644
--- a/Objects/funcobject.c
+++ b/Objects/funcobject.c
@@ -4,6 +4,7 @@
 #include "Python.h"
 #include "pycore_ceval.h"         // _PyEval_BuiltinsFromGlobals()
 #include "pycore_object.h"        // _PyObject_GC_UNTRACK()
+#include "pycore_pyerrors.h"      // _PyErr_Occurred()
 #include "structmember.h"         // PyMemberDef
 
 PyObject *
@@ -13,6 +14,8 @@ PyFunction_NewWithQualName(PyObject *code, PyObject *globals, PyObject *qualname
     assert(PyDict_Check(globals));
     Py_INCREF(globals);
 
+    PyThreadState *tstate = _PyThreadState_GET();
+
     PyCodeObject *code_obj = (PyCodeObject *)code;
     Py_INCREF(code_obj);
 
@@ -42,15 +45,16 @@ PyFunction_NewWithQualName(PyObject *code, PyObject *globals, PyObject *qualname
     _Py_IDENTIFIER(__name__);
     PyObject *module = _PyDict_GetItemIdWithError(globals, &PyId___name__);
     PyObject *builtins = NULL;
-    if (module == NULL && PyErr_Occurred()) {
+    if (module == NULL && _PyErr_Occurred(tstate)) {
         goto error;
     }
     Py_XINCREF(module);
 
-    builtins = _PyEval_BuiltinsFromGlobals(globals);
+    builtins = _PyEval_BuiltinsFromGlobals(tstate, globals);
     if (builtins == NULL) {
         goto error;
     }
+    Py_INCREF(builtins);
 
     PyFunctionObject *op = PyObject_GC_New(PyFunctionObject, &PyFunction_Type);
     if (op == NULL) {