gh-130163: Fix crashes related to PySys_GetObject() (GH-130503)

The use of PySys_GetObject() and _PySys_GetAttr(), which return a borrowed
reference, has been replaced by using one of the following functions, which
return a strong reference and distinguish a missing attribute from an error:
_PySys_GetOptionalAttr(), _PySys_GetOptionalAttrString(),
_PySys_GetRequiredAttr(), and _PySys_GetRequiredAttrString().

Modules/syslogmodule.c

@@ -56,6 +56,7 @@ Revision history:
 
 #include "Python.h"
 #include "osdefs.h"               // SEP
+#include "pycore_sysmodule.h"     // _PySys_GetOptionalAttrString()
 
 #include <syslog.h>
 
@@ -89,45 +90,50 @@ syslog_get_argv(void)
     Py_ssize_t argv_len, scriptlen;
     PyObject *scriptobj;
     Py_ssize_t slash;
-    PyObject *argv = PySys_GetObject("argv");
+    PyObject *argv;
 
-    if (argv == NULL) {
-        return(NULL);
+    if (_PySys_GetOptionalAttrString("argv", &argv) <= 0) {
+        return NULL;
     }
 
     argv_len = PyList_Size(argv);
     if (argv_len == -1) {
         PyErr_Clear();
-        return(NULL);
+        Py_DECREF(argv);
+        return NULL;
     }
     if (argv_len == 0) {
-        return(NULL);
+        Py_DECREF(argv);
+        return NULL;
     }
 
     scriptobj = PyList_GetItem(argv, 0);
+    Py_XINCREF(scriptobj);
+    Py_DECREF(argv);
     if (scriptobj == NULL) {
         PyErr_Clear();
         return NULL;
     }
     if (!PyUnicode_Check(scriptobj)) {
-        return(NULL);
+        Py_DECREF(scriptobj);
+        return NULL;
     }
     scriptlen = PyUnicode_GET_LENGTH(scriptobj);
     if (scriptlen == 0) {
-        return(NULL);
+        Py_DECREF(scriptobj);
+        return NULL;
     }
 
     slash = PyUnicode_FindChar(scriptobj, SEP, 0, scriptlen, -1);
     if (slash == -2) {
         PyErr_Clear();
+        Py_DECREF(scriptobj);
         return NULL;
     }
     if (slash != -1) {
-        return PyUnicode_Substring(scriptobj, slash + 1, scriptlen);
-    } else {
-        Py_INCREF(scriptobj);
-        return(scriptobj);
+        Py_SETREF(scriptobj, PyUnicode_Substring(scriptobj, slash + 1, scriptlen));
     }
+    return scriptobj;
 }
 
 
@@ -162,6 +168,9 @@ syslog_openlog_impl(PyObject *module, PyObject *ident, long logopt,
     else {
         /* get sys.argv[0] or NULL if we can't for some reason  */
         ident = syslog_get_argv();
+        if (ident == NULL && PyErr_Occurred()) {
+            return NULL;
+        }
     }
 
     /* At this point, ident should be INCREF()ed.  openlog(3) does not