python: Use new Py_SET_SIZE API introduced in Python 3.9

Fixes compile error using Python 3.10 while keeping backwards compatibility

CONTRIBUTORS

@@ -38,3 +38,4 @@ Alexandre Bonnetain
 Darvame Hleran
 Sokolov Yura <[email protected]>
 Marcin Lulek <[email protected]>
+Derzsi Dániel <[email protected]>

plugins/python/uwsgi_pymodule.c

@@ -2039,7 +2039,7 @@ PyObject *py_uwsgi_sharedarea_read(PyObject * self, PyObject * args) {
         }
 
 	// HACK: we are safe as rlen can only be lower or equal to len
-	Py_SIZE(ret) = rlen;
+	Py_SET_SIZE((PyVarObject *) ret, rlen);
 
 	return ret;
 }

plugins/python/uwsgi_python.h

@@ -42,9 +42,9 @@
 #define PYTHREE
 #endif
 
-#if (PY_VERSION_HEX < 0x02060000)
-#ifndef Py_SIZE
-#define Py_SIZE(ob)             (((PyVarObject*)(ob))->ob_size)
+#if (PY_VERSION_HEX < 0x03090000)
+#ifndef Py_SET_SIZE
+#define Py_SET_SIZE(o, size) ((o)->ob_size = (size))
 #endif
 #endif