Issue #22821: Fixed fcntl() with integer argument on 64-bit big-endian

platforms.

Misc/NEWS

@@ -183,6 +183,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #22821: Fixed fcntl() with integer argument on 64-bit big-endian
+  platforms.
+
 - Issue #21650: Add an `--sort-keys` option to json.tool CLI.
 
 - Issues #814253, #9179: Group references and conditional group references now

Modules/fcntlmodule.c

@@ -60,7 +60,7 @@ static PyObject *
 fcntl_fcntl_impl(PyModuleDef *module, int fd, int code, PyObject *arg)
 /*[clinic end generated code: output=afc5bfa74a03ef0d input=4850c13a41e86930]*/
 {
-    int int_arg = 0;
+    unsigned int int_arg = 0;
     int ret;
     char *str;
     Py_ssize_t len;
@@ -88,7 +88,7 @@ fcntl_fcntl_impl(PyModuleDef *module, int fd, int code, PyObject *arg)
 
         PyErr_Clear();
         parse_result = PyArg_Parse(arg,
-            "l;fcntl requires a file or file descriptor,"
+            "I;fcntl requires a file or file descriptor,"
             " an integer and optionally a third integer or a string",
             &int_arg);
         if (!parse_result) {
@@ -97,7 +97,7 @@ fcntl_fcntl_impl(PyModuleDef *module, int fd, int code, PyObject *arg)
     }
 
     Py_BEGIN_ALLOW_THREADS
-    ret = fcntl(fd, code, int_arg);
+    ret = fcntl(fd, code, (int)int_arg);
     Py_END_ALLOW_THREADS
     if (ret < 0) {
         PyErr_SetFromErrno(PyExc_IOError);