Based on patch by Zdenek Dohnal obtained from
https://bugs.launchpad.net/hplip/+bug/1933973

diff -pru hplip-3.21.8/io/mudext/hpmudext.c hplip-3.21.8-patched/io/mudext/hpmudext.c
--- hplip-3.21.8/io/mudext/hpmudext.c	2021-09-01 16:10:17.000000000 +0100
+++ hplip-3.21.8-patched/io/mudext/hpmudext.c	2021-10-22 08:30:38.600922861 +0100
@@ -24,6 +24,8 @@ Authors: Don Welch, David Suffield, Naga
 
 \*****************************************************************************/
 
+#define PY_SSIZE_T_CLEAN
+
 #include <Python.h>
 #include <stdarg.h>
 #include "hpmud.h"
@@ -187,14 +189,22 @@ static PyObject *write_channel(PyObject
     HPMUD_CHANNEL cd;
     int timeout = 30;
     char * buf;
-    int buf_size = 0;
+    Py_ssize_t buf_size = 0;
+    int buf_size_asInt = 0;
     int bytes_written = 0;
 
     if (!PyArg_ParseTuple(args, "iis#|i", &dd, &cd, &buf, &buf_size, &timeout))
         return NULL;
 
+    if (buf_size < INT_MIN)
+      buf_size_asInt = INT_MIN;
+    else if (buf_size > INT_MAX)
+      buf_size_asInt = INT_MAX;
+    else
+      buf_size_asInt = (int)buf_size;
+
     Py_BEGIN_ALLOW_THREADS
-    result = hpmud_write_channel(dd, cd, buf, buf_size,  timeout, &bytes_written);
+    result = hpmud_write_channel(dd, cd, buf, buf_size_asInt,  timeout, &bytes_written);
     Py_END_ALLOW_THREADS
 
     return Py_BuildValue("(ii)", result, bytes_written);
@@ -231,14 +241,22 @@ static PyObject *set_pml(PyObject *self,
     char * oid;
     int type;
     char * data;
-    int data_size;
+    Py_ssize_t data_size = 0;
+    int data_size_asInt = 0;
     int pml_result;
 
     if (!PyArg_ParseTuple(args, "iisis#", &dd, &cd, &oid, &type, &data, &data_size))
         return NULL;
 
+    if (data_size < INT_MIN)
+      data_size_asInt = INT_MIN;
+    else if (data_size > INT_MAX)
+      data_size_asInt = INT_MAX;
+    else
+      data_size_asInt = (int)data_size;
+
     Py_BEGIN_ALLOW_THREADS
-    result = hpmud_set_pml(dd, cd, oid, type, (void *)data, data_size, &pml_result);
+    result = hpmud_set_pml(dd, cd, oid, type, (void *)data, data_size_asInt, &pml_result);
     Py_END_ALLOW_THREADS
 
     return Py_BuildValue("(ii)", result, pml_result);
diff -pru hplip-3.21.8/pcard/pcardext/pcardext.c hplip-3.21.8-patched/pcard/pcardext/pcardext.c
--- hplip-3.21.8/pcard/pcardext/pcardext.c	2021-09-01 16:10:17.000000000 +0100
+++ hplip-3.21.8-patched/pcard/pcardext/pcardext.c	2021-10-22 08:24:11.010798381 +0100
@@ -24,6 +24,8 @@ Author: Don Welch
 
 \*****************************************************************************/
 
+#define PY_SSIZE_T_CLEAN
+
 #include <Python.h>
 #include <structmember.h>
 #include "../fat.h"
diff -pru hplip-3.21.8/prnt/cupsext/cupsext.c hplip-3.21.8-patched/prnt/cupsext/cupsext.c
--- hplip-3.21.8/prnt/cupsext/cupsext.c	2021-09-01 16:10:17.000000000 +0100
+++ hplip-3.21.8-patched/prnt/cupsext/cupsext.c	2021-10-22 08:26:30.975843330 +0100
@@ -73,6 +73,7 @@ Yashwant Kumar Sahu
 Sanjay Kumar
 */
 
+#define PY_SSIZE_T_CLEAN
 
 #include <Python.h>
 #include <structmember.h>
diff -pru hplip-3.21.8/scan/scanext/scanext.c hplip-3.21.8-patched/scan/scanext/scanext.c
--- hplip-3.21.8/scan/scanext/scanext.c	2021-09-01 16:10:17.000000000 +0100
+++ hplip-3.21.8-patched/scan/scanext/scanext.c	2021-10-21 21:31:23.074739743 +0100
@@ -45,6 +45,8 @@ PERFORMANCE OF THIS SOFTWARE.
 *******************************************************************/
 
 
+#define PY_SSIZE_T_CLEAN
+
 /* _ScanDevice objects */
 
 #include "Python.h"
