gh-94936: C getters: co_varnames, co_cellvars, co_freevars (GH-95008)

(cherry picked from commit 42b102b)

Co-authored-by: Ken Jin <[email protected]>

Author: miss-islington

Doc/c-api/code.rst

@@ -90,3 +90,28 @@ bound into a function.
 
    .. versionadded:: 3.11
 
+.. c:function:: PyObject* PyCode_GetVarnames(PyCodeObject *co)
+
+   Equivalent to the Python code ``getattr(co, 'co_varnames')``.
+   Returns a new reference to a :c:type:`PyTupleObject` containing the names of
+   the local variables. On error, ``NULL`` is returned and an exception
+   is raised.
+
+   .. versionadded:: 3.11
+
+.. c:function:: PyObject* PyCode_GetCellvars(PyCodeObject *co)
+
+   Equivalent to the Python code ``getattr(co, 'co_cellvars')``.
+   Returns a new reference to a :c:type:`PyTupleObject` containing the names of
+   the local variables that are referenced by nested functions. On error, ``NULL``
+   is returned and an exception is raised.
+
+   .. versionadded:: 3.11
+
+.. c:function:: PyObject* PyCode_GetFreevars(PyCodeObject *co)
+
+   Equivalent to the Python code ``getattr(co, 'co_freevars')``.
+   Returns a new reference to a :c:type:`PyTupleObject` containing the names of
+   the free variables. On error, ``NULL`` is returned and an exception is raised.
+
+   .. versionadded:: 3.11

Doc/whatsnew/3.11.rst

@@ -1724,10 +1724,13 @@ Porting to Python 3.11
   To get a custom code object: create a code object using the compiler,
   then get a modified version with the ``replace`` method.
 
-* :c:type:`PyCodeObject` no longer has a ``co_code`` field.  Instead,
-  use ``PyObject_GetAttrString(code_object, "co_code")`` or
-  :c:func:`PyCode_GetCode` to get the underlying bytes object.
-  (Contributed by Brandt Bucher in :issue:`46841` and Ken Jin in :gh:`92154`.)
+* :c:type:`PyCodeObject` no longer has the ``co_code``, ``co_varnames``,
+  ``co_cellvars`` and ``co_freevars`` fields.  Instead, use
+  :c:func:`PyCode_GetCode`, :c:func:`PyCode_GetVarnames`,
+  :c:func:`PyCode_GetCellvars` and :c:func:`PyCode_GetFreevars` respectively
+  to access them via the C API.
+  (Contributed by Brandt Bucher in :issue:`46841` and Ken Jin in :gh:`92154`
+  and :gh:`94936`.)
 
 * The old trashcan macros (``Py_TRASHCAN_SAFE_BEGIN``/``Py_TRASHCAN_SAFE_END``)
   are now deprecated. They should be replaced by the new macros

Include/cpython/code.h

@@ -209,6 +209,12 @@ PyAPI_FUNC(int) _PyCode_SetExtra(PyObject *code, Py_ssize_t index,
 /* Equivalent to getattr(code, 'co_code') in Python.
    Returns a strong reference to a bytes object. */
 PyAPI_FUNC(PyObject *) PyCode_GetCode(PyCodeObject *code);
+/* Equivalent to getattr(code, 'co_varnames') in Python. */
+PyAPI_FUNC(PyObject *) PyCode_GetVarnames(PyCodeObject *code);
+/* Equivalent to getattr(code, 'co_cellvars') in Python. */
+PyAPI_FUNC(PyObject *) PyCode_GetCellvars(PyCodeObject *code);
+/* Equivalent to getattr(code, 'co_freevars') in Python. */
+PyAPI_FUNC(PyObject *) PyCode_GetFreevars(PyCodeObject *code);
 
 typedef enum _PyCodeLocationInfoKind {
     /* short forms are 0 to 9 */

Misc/NEWS.d/next/C API/2022-07-19-22-37-40.gh-issue-94936.LGlmKv.rst

@@ -0,0 +1,3 @@
+Added :c:func:`PyCode_GetVarnames`, :c:func:`PyCode_GetCellvars` and
+:c:func:`PyCode_GetFreevars` for accessing ``co_varnames``, ``co_cellvars``
+and ``co_freevars`` respectively via the C API.

Modules/_testcapimodule.c

@@ -5952,21 +5952,79 @@ test_code_api(PyObject *self, PyObject *Py_UNUSED(args))
     if (co == NULL) {
         return NULL;
     }
-    PyObject *co_code = PyCode_GetCode(co);
-    if (co_code == NULL) {
-        Py_DECREF(co);
-        return NULL;
-    }
-    assert(PyBytes_CheckExact(co_code));
-    if (PyObject_Length(co_code) == 0) {
-        PyErr_SetString(PyExc_ValueError, "empty co_code");
-        Py_DECREF(co);
+    /* co_code */
+    {
+        PyObject *co_code = PyCode_GetCode(co);
+        if (co_code == NULL) {
+            goto fail;
+        }
+        assert(PyBytes_CheckExact(co_code));
+        if (PyObject_Length(co_code) == 0) {
+            PyErr_SetString(PyExc_ValueError, "empty co_code");
+            Py_DECREF(co_code);
+            goto fail;
+        }
         Py_DECREF(co_code);
-        return NULL;
+    }
+    /* co_varnames */
+    {
+        PyObject *co_varnames = PyCode_GetVarnames(co);
+        if (co_varnames == NULL) {
+            goto fail;
+        }
+        if (!PyTuple_CheckExact(co_varnames)) {
+            PyErr_SetString(PyExc_TypeError, "co_varnames not tuple");
+            Py_DECREF(co_varnames);
+            goto fail;
+        }
+        if (PyTuple_GET_SIZE(co_varnames) != 0) {
+            PyErr_SetString(PyExc_ValueError, "non-empty co_varnames");
+            Py_DECREF(co_varnames);
+            goto fail;
+        }
+        Py_DECREF(co_varnames);
+    }
+    /* co_cellvars */
+    {
+        PyObject *co_cellvars = PyCode_GetCellvars(co);
+        if (co_cellvars == NULL) {
+            goto fail;
+        }
+        if (!PyTuple_CheckExact(co_cellvars)) {
+            PyErr_SetString(PyExc_TypeError, "co_cellvars not tuple");
+            Py_DECREF(co_cellvars);
+            goto fail;
+        }
+        if (PyTuple_GET_SIZE(co_cellvars) != 0) {
+            PyErr_SetString(PyExc_ValueError, "non-empty co_cellvars");
+            Py_DECREF(co_cellvars);
+            goto fail;
+        }
+        Py_DECREF(co_cellvars);
+    }
+    /* co_freevars */
+    {
+        PyObject *co_freevars = PyCode_GetFreevars(co);
+        if (co_freevars == NULL) {
+            goto fail;
+        }
+        if (!PyTuple_CheckExact(co_freevars)) {
+            PyErr_SetString(PyExc_TypeError, "co_freevars not tuple");
+            Py_DECREF(co_freevars);
+            goto fail;
+        }
+        if (PyTuple_GET_SIZE(co_freevars) != 0) {
+            PyErr_SetString(PyExc_ValueError, "non-empty co_freevars");
+            Py_DECREF(co_freevars);
+            goto fail;
+        }
+        Py_DECREF(co_freevars);
     }
     Py_DECREF(co);
-    Py_DECREF(co_code);
     Py_RETURN_NONE;
+fail:
+    Py_DECREF(co);
+    return NULL;
 }
 
 static int

Objects/codeobject.c

@@ -1399,18 +1399,36 @@ _PyCode_GetVarnames(PyCodeObject *co)
     return get_localsplus_names(co, CO_FAST_LOCAL, co->co_nlocals);
 }
 
+PyObject *
+PyCode_GetVarnames(PyCodeObject *code)
+{
+    return _PyCode_GetVarnames(code);
+}
+
 PyObject *
 _PyCode_GetCellvars(PyCodeObject *co)
 {
     return get_localsplus_names(co, CO_FAST_CELL, co->co_ncellvars);
 }
 
+PyObject *
+PyCode_GetCellvars(PyCodeObject *code)
+{
+    return _PyCode_GetCellvars(code);
+}
+
 PyObject *
 _PyCode_GetFreevars(PyCodeObject *co)
 {
     return get_localsplus_names(co, CO_FAST_FREE, co->co_nfreevars);
 }
 
+PyObject *
+PyCode_GetFreevars(PyCodeObject *code)
+{
+    return _PyCode_GetFreevars(code);
+}
+
 static void
 deopt_code(_Py_CODEUNIT *instructions, Py_ssize_t len)
 {