python · serhiy-storchaka · May 28, 2025 · Sep 20, 2023 · Oct 18, 2023 · Oct 18, 2023
@@ -1417,7 +1417,7 @@ initialization::
 
         /* Specify sys.path explicitly */
         /* If you want to modify the default set of paths, finish
-           initialization first and then use PySys_GetObject("path") */
+           initialization first and then use PySys_GetAttr("path") */
         config.module_search_paths_set = 1;
         status = PyWideStringList_Append(&config.module_search_paths,
                                          L"/path/to/stdlib");

diff --git a/Doc/c-api/sys.rst b/Doc/c-api/sys.rst
@@ -222,10 +222,55 @@ These are utility functions that make functionality from the :mod:`sys` module
 accessible to C code.  They all work with the current interpreter thread's
 :mod:`sys` module's dict, which is contained in the internal thread state structure.
 
+.. c:function:: PyObject *PySys_GetAttr(PyObject *name)
+
+   Get the attribute *name* of the :mod:`sys` module. Return a :term:`strong reference`.
+   Raise :exc:`RuntimeError` and return ``NULL`` if it does not exist.
-   Raise :exc:`RuntimeError` and return ``NULL`` if it does not exist.
+   Raise :exc:`RuntimeError` and return ``NULL`` if it does not exist or if the :mod:`sys` module cannot be found.
-   Raise :exc:`RuntimeError` and return ``NULL`` if it does not exist.
+   Raise :exc:`RuntimeError` and return ``NULL`` if it does not exist or if the :mod:`sys` module cannot be found.
+
+   If the non-existing object should not be treated as a failure, you can use
+   :c:func:`PySys_GetOptionalAttr` instead.
+
+   .. versionadded:: 3.13
+
+.. c:function:: PyObject *PySys_GetAttrString(const char *name)
+
+   This is the same as :c:func:`PySys_GetAttr`, but *name* is
+   specified as a :c:expr:`const char*` UTF-8 encoded bytes string,
+   rather than a :c:expr:`PyObject*`.
+
+   If the non-existing object should not be treated as a failure, you can use
+   :c:func:`PySys_GetOptionalAttrString` instead.
+
+   .. versionadded:: 3.13
+
+.. c:function:: int PySys_GetOptionalAttr(PyObject *name, PyObject **result);
+
+   Variant of :c:func:`PySys_GetAttr` which doesn't raise
+   exception if the object does not exist.
+
+   If the object exists, set *\*result* to a new :term:`strong reference`
+   to the object and return ``1``.
+   If the object does not exist, set *\*result* to ``NULL`` and return ``0``,
+   without setting an exception.
+   If other error occurred, set an exception, set *\*result* to ``NULL`` and
+   return ``-1``.
-   If the object exists, set *\*result* to a new :term:`strong reference`
-   to the object and return ``1``.
-   If the object does not exist, set *\*result* to ``NULL`` and return ``0``,
-   without setting an exception.
-   If other error occurred, set an exception, set *\*result* to ``NULL`` and
-   return ``-1``.
+   * Return ``1`` and set *\*result* to a new :term:`strong reference`
+     to the object if the attribute exists.
+   * Return ``0`` without setting an exception and set *\*result* to ``NULL``
+     if the attribute does not exist.
+   * Return ``-1``, set an exception and set *\*result* to ``NULL``
+     if an error occurred.
-   If the object exists, set *\*result* to a new :term:`strong reference`
-   to the object and return ``1``.
-   If the object does not exist, set *\*result* to ``NULL`` and return ``0``,
-   without setting an exception.
-   If other error occurred, set an exception, set *\*result* to ``NULL`` and
-   return ``-1``.
+   * Return ``1`` and set *\*result* to a new :term:`strong reference`
+     to the object if the attribute exists.
+   * Return ``0`` without setting an exception and set *\*result* to ``NULL``
+     if the attribute does not exist.
+   * Return ``-1``, set an exception and set *\*result* to ``NULL``
+     if an error occurred.
+
+   .. versionadded:: 3.13
+
+.. c:function:: int PySys_GetOptionalAttrString(const char *name, PyObject **result);
+
+   This is the same as :c:func:`PySys_GetOptionalAttr`, but *name* is
+   specified as a :c:expr:`const char*` UTF-8 encoded bytes string,
+   rather than a :c:expr:`PyObject*`.
+
+   .. versionadded:: 3.13
+
 .. c:function:: PyObject *PySys_GetObject(const char *name)
 
-   Return the object *name* from the :mod:`sys` module or ``NULL`` if it does
-   not exist, without setting an exception.
+   Similar to :c:func:`PySys_GetAttrString`, but return a :term:`borrowed
+   reference` and return ``NULL`` *without* setting exception on failure.
+
+   Preserves exception that was set before the call.
 
 .. c:function:: int PySys_SetObject(const char *name, PyObject *v)
 

diff --git a/Include/cpython/sysmodule.h b/Include/cpython/sysmodule.h
@@ -10,6 +10,11 @@ PyAPI_FUNC(int) PySys_Audit(
     ...);
 PyAPI_FUNC(int) PySys_AddAuditHook(Py_AuditHookFunction, void*);
 
+PyAPI_FUNC(PyObject *) PySys_GetAttr(PyObject *);
+PyAPI_FUNC(PyObject *) PySys_GetAttrString(const char *);
+PyAPI_FUNC(int) PySys_GetOptionalAttr(PyObject *, PyObject **);
+PyAPI_FUNC(int) PySys_GetOptionalAttrString(const char *, PyObject **);
+
 typedef struct {
     FILE* perf_map;
     PyThread_type_lock map_lock;

@@ -8,9 +8,6 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
-// Export for '_pickle' shared extension
-PyAPI_FUNC(PyObject*) _PySys_GetAttr(PyThreadState *tstate, PyObject *name);
-
 // Export for '_pickle' shared extension
 PyAPI_FUNC(size_t) _PySys_GetSizeOf(PyObject *);
 

diff --git a/Lib/test/test_capi/test_misc.py b/Lib/test/test_capi/test_misc.py
@@ -1098,6 +1098,54 @@ class Data(_testcapi.ObjExtraData):
         del d.extra
         self.assertIsNone(d.extra)
 
+    def test_sys_getattr(self):
+        sys_getattr = _testcapi.sys_getattr
+
+        self.assertIs(sys_getattr('stdout'), sys.stdout)
+        with support.swap_attr(sys, '\U0001f40d', 42):
+            self.assertEqual(sys_getattr('\U0001f40d'), 42)
+
+        with self.assertRaisesRegex(RuntimeError, r'lost sys\.nonexisting'):
+            sys_getattr('nonexisting')
+        self.assertRaises(TypeError, sys_getattr, 1)
+        self.assertRaises(TypeError, sys_getattr, [])
+        # CRASHES sys_getattr(NULL)
+
+    def test_sys_getattrstring(self):
+        getattrstring = _testcapi.sys_getattrstring
+
+        self.assertIs(getattrstring(b'stdout'), sys.stdout)
+        with support.swap_attr(sys, '\U0001f40d', 42):
+            self.assertEqual(getattrstring('\U0001f40d'.encode()), 42)
+
+        with self.assertRaisesRegex(RuntimeError, r'lost sys\.nonexisting'):
+            getattrstring(b'nonexisting')
+        self.assertRaises(UnicodeDecodeError, getattrstring, b'\xff')
+        # CRASHES getattrstring(NULL)
+    
+    def test_sys_getoptionalattr(self):
+        getoptionalattr = _testcapi.sys_getoptionalattr
+
+        self.assertIs(getoptionalattr('stdout'), sys.stdout)
+        with support.swap_attr(sys, '\U0001f40d', 42):
+            self.assertEqual(getoptionalattr('\U0001f40d'), 42)
+
+        self.assertIs(getoptionalattr('nonexisting'), AttributeError)
+        self.assertRaises(TypeError, getoptionalattr, 1)
+        self.assertRaises(TypeError, getoptionalattr, [])
+        # CRASHES getoptionalattr(NULL)
+
+    def test_sys_getoptionalattrstring(self):
+        getoptionalattrstring = _testcapi.sys_getoptionalattrstring
+
+        self.assertIs(getoptionalattrstring(b'stdout'), sys.stdout)
+        with support.swap_attr(sys, '\U0001f40d', 42):
+            self.assertEqual(getoptionalattrstring('\U0001f40d'.encode()), 42)
+
+        self.assertIs(getoptionalattrstring(b'nonexisting'), AttributeError)
+        self.assertRaises(UnicodeDecodeError, getoptionalattrstring, b'\xff')
+        # CRASHES getoptionalattrstring(NULL)
+
     def test_sys_getobject(self):
         getobject = _testcapi.sys_getobject
 

diff --git a/Misc/NEWS.d/next/C API/2023-10-18-14-36-35.gh-issue-108512.fMZLfr.rst b/Misc/NEWS.d/next/C API/2023-10-18-14-36-35.gh-issue-108512.fMZLfr.rst
@@ -0,0 +1,2 @@
+Add private functions :c:func:`PySys_GetAttr`, :c:func:`PySys_GetAttrString`,
+:c:func:`PySys_GetOptionalAttr` and :c:func:`PySys_GetOptionalAttrString`.
diff --git a/Modules/_ctypes/callbacks.c b/Modules/_ctypes/callbacks.c
@@ -82,22 +82,6 @@ PyType_Spec cthunk_spec = {
 
 /**************************************************************/
 
-static void
-PrintError(const char *msg, ...)
-{
-    char buf[512];
-    PyObject *f = PySys_GetObject("stderr");
-    va_list marker;
-
-    va_start(marker, msg);
-    PyOS_vsnprintf(buf, sizeof(buf), msg, marker);
-    va_end(marker);
-    if (f != NULL && f != Py_None)
-        PyFile_WriteString(buf, f);
-    PyErr_Print();
-}
-
-
 #ifdef MS_WIN32
 /*
  * We must call AddRef() on non-NULL COM pointers we receive as arguments
@@ -116,7 +100,7 @@ TryAddRef(StgDictObject *dict, CDataObject *obj)
     int r = PyDict_Contains((PyObject *)dict, &_Py_ID(_needs_com_addref_));
     if (r <= 0) {
         if (r < 0) {
-            PrintError("getting _needs_com_addref_");
+            PySys_WriteStderr("getting _needs_com_addref_");
         }
         return;
     }
@@ -160,7 +144,7 @@ static void _CallPythonObject(void *mem,
         if (dict && dict->getfunc && !_ctypes_simple_instance(cnv)) {
             PyObject *v = dict->getfunc(*pArgs, dict->size);
             if (!v) {
-                PrintError("create argument %zd:\n", i);
+                PySys_WriteStderr("create argument %zd:\n", i);
                 goto Done;
             }
             args[i] = v;
@@ -173,12 +157,12 @@ static void _CallPythonObject(void *mem,
             /* Hm, shouldn't we use PyCData_AtAddress() or something like that instead? */
             CDataObject *obj = (CDataObject *)_PyObject_CallNoArgs(cnv);
             if (!obj) {
-                PrintError("create argument %zd:\n", i);
+                PySys_WriteStderr("create argument %zd:\n", i);
                 goto Done;
             }
             if (!CDataObject_Check(obj)) {
                 Py_DECREF(obj);
-                PrintError("unexpected result of create argument %zd:\n", i);
+                PySys_WriteStderr("unexpected result of create argument %zd:\n", i);
                 goto Done;
             }
             memcpy(obj->b_ptr, *pArgs, dict->size);
@@ -189,7 +173,7 @@ static void _CallPythonObject(void *mem,
         } else {
             PyErr_SetString(PyExc_TypeError,
                             "cannot build parameter");
-            PrintError("Parsing argument %zd\n", i);
+            PySys_WriteStderr("Parsing argument %zd\n", i);
             goto Done;
         }
         /* XXX error handling! */

diff --git a/Modules/_cursesmodule.c b/Modules/_cursesmodule.c
@@ -3373,17 +3373,19 @@ _curses_setupterm_impl(PyObject *module, const char *term, int fd)
     if (fd == -1) {
         PyObject* sys_stdout;
 
-        sys_stdout = PySys_GetObject("stdout");
+        sys_stdout = PySys_GetAttrString("stdout");
+        if (sys_stdout == NULL) {
+            return NULL;
+        }
 
-        if (sys_stdout == NULL || sys_stdout == Py_None) {
-            PyErr_SetString(
-                PyCursesError,
-                "lost sys.stdout");
+        if (sys_stdout == Py_None) {
+            PyErr_SetString(PyCursesError, "lost sys.stdout");
+            Py_DECREF(sys_stdout);
             return NULL;
         }
 
         fd = PyObject_AsFileDescriptor(sys_stdout);
-
+        Py_DECREF(sys_stdout);
         if (fd == -1) {
             return NULL;
         }

diff --git a/Modules/_lsprof.c b/Modules/_lsprof.c
@@ -716,7 +716,7 @@ profiler_enable(ProfilerObject *self, PyObject *args, PyObject *kwds)
         return NULL;
     }
 
-    PyObject* monitoring = _PyImport_GetModuleAttrString("sys", "monitoring");
+    PyObject* monitoring = PySys_GetAttrString("monitoring");
     if (!monitoring) {
         return NULL;
     }
@@ -778,7 +778,7 @@ profiler_disable(ProfilerObject *self, PyObject* noarg)
 {
     if (self->flags & POF_ENABLED) {
         PyObject* result = NULL;
-        PyObject* monitoring = _PyImport_GetModuleAttrString("sys", "monitoring");
+        PyObject* monitoring = PySys_GetAttrString("monitoring");
 
         if (!monitoring) {
             return NULL;
@@ -880,7 +880,7 @@ profiler_init(ProfilerObject *pObj, PyObject *args, PyObject *kw)
     Py_XSETREF(pObj->externalTimer, Py_XNewRef(timer));
     pObj->tool_id = PY_MONITORING_PROFILER_ID;
 
-    PyObject* monitoring = _PyImport_GetModuleAttrString("sys", "monitoring");
+    PyObject* monitoring = PySys_GetAttrString("monitoring");
     if (!monitoring) {
         return -1;
     }

diff --git a/Modules/_pickle.c b/Modules/_pickle.c
@@ -17,7 +17,7 @@
 #include "pycore_pystate.h"       // _PyThreadState_GET()
 #include "pycore_runtime.h"       // _Py_ID()
 #include "pycore_setobject.h"     // _PySet_NextEntry()
-#include "pycore_sysmodule.h"     // _PySys_GetAttr()
+#include "pycore_sysmodule.h"     // _PySys_GetSizeOf()
 
 #include <stdlib.h>               // strtol()
 
@@ -1986,49 +1986,54 @@ whichmodule(PyObject *global, PyObject *dotted_path)
     assert(module_name == NULL);
 
     /* Fallback on walking sys.modules */
-        PyThreadState *tstate = _PyThreadState_GET();
-    modules = _PySys_GetAttr(tstate, &_Py_ID(modules));
+    modules = PySys_GetAttr(&_Py_ID(modules));
     if (modules == NULL) {
-        PyErr_SetString(PyExc_RuntimeError, "unable to get sys.modules");
         return NULL;
     }
     if (PyDict_CheckExact(modules)) {
         i = 0;
         while (PyDict_Next(modules, &i, &module_name, &module)) {
             if (_checkmodule(module_name, module, global, dotted_path) == 0) {
+                Py_DECREF(modules);
                 return Py_NewRef(module_name);
             }
             if (PyErr_Occurred()) {
+                Py_DECREF(modules);
                 return NULL;
             }
         }
     }
     else {
         PyObject *iterator = PyObject_GetIter(modules);
         if (iterator == NULL) {
+            Py_DECREF(modules);
             return NULL;
         }
         while ((module_name = PyIter_Next(iterator))) {
             module = PyObject_GetItem(modules, module_name);
             if (module == NULL) {
                 Py_DECREF(module_name);
                 Py_DECREF(iterator);
+                Py_DECREF(modules);
                 return NULL;
             }
             if (_checkmodule(module_name, module, global, dotted_path) == 0) {
                 Py_DECREF(module);
                 Py_DECREF(iterator);
+                Py_DECREF(modules);
                 return module_name;
             }
             Py_DECREF(module);
             Py_DECREF(module_name);
             if (PyErr_Occurred()) {
                 Py_DECREF(iterator);
+                Py_DECREF(modules);
                 return NULL;
             }
         }
         Py_DECREF(iterator);
     }
+    Py_DECREF(modules);
 
     /* If no module is found, use __main__. */
     return &_Py_ID(__main__);
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		Add private functions :c:func:`PySys_GetAttr`, :c:func:`PySys_GetAttrString`,
		:c:func:`PySys_GetOptionalAttr` and :c:func:`PySys_GetOptionalAttrString`.