Add safety cast in queue tutorial code that avoids casting a potentially...

Add safety cast in queue tutorial code that avoids casting a potentially non-pointer-sized "int" to a "void*".

docs/examples/tutorial/clibraries/queue3.pyx

-# queue.pyx
-
-cimport cqueue
-
-cdef class Queue:
-    """A queue class for C integer values.
-
-    >>> q = Queue()
-    >>> q.append(5)
-    >>> q.peek()
-    5
-    >>> q.pop()
-    5
-    """
-    cdef cqueue.Queue* _c_queue
-    def __cinit__(self):
-        self._c_queue = cqueue.queue_new()
-        if self._c_queue is NULL:
-            raise MemoryError()
-
-    def __dealloc__(self):
-        if self._c_queue is not NULL:
-            cqueue.queue_free(self._c_queue)
-
-    cpdef append(self, int value):
-        if not cqueue.queue_push_tail(self._c_queue,
-                                      <void*> value):
-            raise MemoryError()
-
-    # The `cpdef` feature is obviously not available for the original "extend()"
-    # method, as the method signature is incompatible with Python argument
-    # types (Python does not have pointers).  However, we can rename
-    # the C-ish "extend()" method to e.g. "extend_ints()", and write
-    # a new "extend()" method that provides a suitable Python interface by
-    # accepting an arbitrary Python iterable.
-    cpdef extend(self, values):
-        for value in values:
-            self.append(value)
-
-    cdef extend_ints(self, int* values, size_t count):
-        cdef int value
-        for value in values[:count]:  # Slicing pointer to limit the iteration boundaries.
-            self.append(value)
-
-    cpdef int peek(self) except? -1:
-        cdef int value = <Py_ssize_t> cqueue.queue_peek_head(self._c_queue)
-
-        if value == 0:
-            # this may mean that the queue is empty,
-            # or that it happens to contain a 0 value
-            if cqueue.queue_is_empty(self._c_queue):
-                raise IndexError("Queue is empty")
-        return value
-
-    cpdef int pop(self) except? -1:
-        if cqueue.queue_is_empty(self._c_queue):
-            raise IndexError("Queue is empty")
-        return <Py_ssize_t> cqueue.queue_pop_head(self._c_queue)
-
-    def __bool__(self):
-        return not cqueue.queue_is_empty(self._c_queue)
+# queue.pyx
+
+cimport cqueue
+
+cdef class Queue:
+    """A queue class for C integer values.
+
+    >>> q = Queue()
+    >>> q.append(5)
+    >>> q.peek()
+    5
+    >>> q.pop()
+    5
+    """
+    cdef cqueue.Queue* _c_queue
+    def __cinit__(self):
+        self._c_queue = cqueue.queue_new()
+        if self._c_queue is NULL:
+            raise MemoryError()
+
+    def __dealloc__(self):
+        if self._c_queue is not NULL:
+            cqueue.queue_free(self._c_queue)
+
+    cpdef append(self, int value):
+        if not cqueue.queue_push_tail(self._c_queue,
+                                      <void*> <Py_ssize_t> value):
+            raise MemoryError()
+
+    # The `cpdef` feature is obviously not available for the original "extend()"
+    # method, as the method signature is incompatible with Python argument
+    # types (Python does not have pointers).  However, we can rename
+    # the C-ish "extend()" method to e.g. "extend_ints()", and write
+    # a new "extend()" method that provides a suitable Python interface by
+    # accepting an arbitrary Python iterable.
+    cpdef extend(self, values):
+        for value in values:
+            self.append(value)
+
+    cdef extend_ints(self, int* values, size_t count):
+        cdef int value
+        for value in values[:count]:  # Slicing pointer to limit the iteration boundaries.
+            self.append(value)
+
+    cpdef int peek(self) except? -1:
+        cdef int value = <Py_ssize_t> cqueue.queue_peek_head(self._c_queue)
+
+        if value == 0:
+            # this may mean that the queue is empty,
+            # or that it happens to contain a 0 value
+            if cqueue.queue_is_empty(self._c_queue):
+                raise IndexError("Queue is empty")
+        return value
+
+    cpdef int pop(self) except? -1:
+        if cqueue.queue_is_empty(self._c_queue):
+            raise IndexError("Queue is empty")
+        return <Py_ssize_t> cqueue.queue_pop_head(self._c_queue)
+
+    def __bool__(self):
+        return not cqueue.queue_is_empty(self._c_queue)