Fix conversion of ctypes pointers passed to C extension

CHANGELOG.rst

@@ -10,6 +10,10 @@ Versioning <https://semver.org/spec/v2.0.0.html>`_.
 Unreleased_
 -----------
 
+Fixed:
+
+- `Fix conversion of ctypes pointers passed to C extension <../../pull/154>`_
+
 4.5.0_ - 2023-12-04
 -------------------
 

softioc/extension.c

@@ -98,9 +98,12 @@ static PyObject *db_put_field(PyObject *self, PyObject *args)
 {
     const char *name;
     short dbrType;
-    void *pbuffer;
+    PyObject *buffer_ptr;
     long length;
-    if (!PyArg_ParseTuple(args, "shnl", &name, &dbrType, &pbuffer, &length))
+    if (!PyArg_ParseTuple(args, "shOl", &name, &dbrType, &buffer_ptr, &length))
+        return NULL;
+    void *pbuffer = PyLong_AsVoidPtr(buffer_ptr);
+    if (!pbuffer)
         return NULL;
 
     struct dbAddr dbAddr;
@@ -110,11 +113,11 @@ static PyObject *db_put_field(PyObject *self, PyObject *args)
 
     long put_result;
     /* There are two important locks to consider at this point: The Global
-     * Interpreter Lock (GIL) and the EPICS record lock. A deadlock is possible if
-     * this thread holds the GIL and wants the record lock (which happens inside
-     * dbPutField), and there exists another EPICS thread that has the record lock
-     * and wants to call Python (which requires the GIL).
-     * This can occur if this code is called as part of an asynchronous on_update
+     * Interpreter Lock (GIL) and the EPICS record lock. A deadlock is possible
+     * if this thread holds the GIL and wants the record lock (which happens
+     * inside dbPutField), and there exists another EPICS thread that has the
+     * record lock and wants to call Python (which requires the GIL).  This can
+     * occur if this code is called as part of an asynchronous on_update
      * callback.
      * Therefore, we must ensure we relinquish the GIL while we perform this
      * EPICS call, to avoid potential deadlocks.
@@ -133,9 +136,12 @@ static PyObject *db_get_field(PyObject *self, PyObject *args)
 {
     const char *name;
     short dbrType;
-    void *pbuffer;
+    PyObject *buffer_ptr;
     long length;
-    if (!PyArg_ParseTuple(args, "shnl", &name, &dbrType, &pbuffer, &length))
+    if (!PyArg_ParseTuple(args, "shOl", &name, &dbrType, &buffer_ptr, &length))
+        return NULL;
+    void *pbuffer = PyLong_AsVoidPtr(buffer_ptr);
+    if (!pbuffer)
         return NULL;
 
     struct dbAddr dbAddr;