gh-108512: Add and use new replacements for PySys_GetObject()

Add functions PySys_GetAttr(), PySys_GetAttrString(),
PySys_GetOptionalAttr() and PySys_GetOptionalAttrString().

Author: serhiy-storchaka

Doc/c-api/init_config.rst

@@ -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");

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)
+
+   Return the object *name* from the :mod:`sys` module or ``NULL`` on failure.
+   Set :exc:`RuntimeError` and return ``NULL`` if it does not exist.
+
+   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``.
+
+   .. 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)
 

Doc/whatsnew/3.13.rst

@@ -988,6 +988,12 @@ New Features
 
   (Contributed by Serhiy Storchaka in :gh:`108511`.)
 
+* Add functions :c:func:`PySys_GetAttr`, :c:func:`PySys_GetAttrString`,
+  :c:func:`PySys_GetOptionalAttr` and :c:func:`PySys_GetOptionalAttrString`.
+  They all are variants of :c:func:`PySys_GetObject` which return a new
+  :term:`strong reference` and can set an exception on failure.
+  (Contributed by Serhiy Storchaka in :gh:`108512`.)
+
 * If Python is built in :ref:`debug mode <debug-build>` or :option:`with
   assertions <--with-assertions>`, :c:func:`PyTuple_SET_ITEM` and
   :c:func:`PyList_SET_ITEM` now check the index argument with an assertion.

Include/internal/pycore_sysmodule.h

@@ -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 *);
 

Include/sysmodule.h

@@ -8,6 +8,12 @@ extern "C" {
 #endif
 
 PyAPI_FUNC(PyObject *) PySys_GetObject(const char *);
+#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x030D0000
+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 **);
+#endif
 PyAPI_FUNC(int) PySys_SetObject(const char *, PyObject *);
 
 PyAPI_FUNC(void) PySys_WriteStdout(const char *format, ...)

Misc/NEWS.d/next/C API/2023-10-18-14-36-35.gh-issue-108512.fMZLfr.rst

@@ -0,0 +1,2 @@
+Add functions :c:func:`PySys_GetAttr`, :c:func:`PySys_GetAttrString`,
+:c:func:`PySys_GetOptionalAttr` and :c:func:`PySys_GetOptionalAttrString`.

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! */

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;
         }

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;
     }

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__);