diff -r eae03e8aef0e Modules/_struct.c
--- a/Modules/_struct.c	Wed Aug 15 16:26:15 2012 +0200
+++ b/Modules/_struct.c	Wed Aug 15 16:39:35 2012 +0200
@@ -9,7 +9,46 @@
 #include "structmember.h"
 #include <ctype.h>
 
-static PyTypeObject PyStructType;
+typedef struct {
+  PyObject *PyStructType;
+  /* Exception */
+  PyObject *StructError;
+  PyObject *cache;
+} _structstate;
+
+
+#define _struct_state(o) ((_structstate *)PyModule_GetState(o))
+
+static int
+_struct_clear(PyObject *m)
+{
+   _structstate *state = _struct_state(m);
+   Py_CLEAR(state->PyStructType);
+   Py_CLEAR(state->StructError);
+   Py_CLEAR(state->cache);
+   return 0;
+}
+
+static int
+_struct_traverse(PyObject *m, visitproc visit, void *arg)
+{
+    _structstate *state = _struct_state(m);
+    Py_VISIT(state->PyStructType);
+    Py_VISIT(state->StructError);
+    Py_VISIT(state->cache);
+    return 0;
+}
+
+static void
+_struct_free(void *m)
+{
+    _struct_clear((PyObject *)m);
+}
+
+static PyModuleDef _structmodule;
+
+#define _structstate_global ((_structstate *)PyModule_GetState(PyState_FindModule(&_structmodule)))
+
 
 /* The translation function for each format character is table driven */
 typedef struct _formatdef {
@@ -40,14 +79,10 @@
 } PyStructObject;
 
 
-#define PyStruct_Check(op) PyObject_TypeCheck(op, &PyStructType)
-#define PyStruct_CheckExact(op) (Py_TYPE(op) == &PyStructType)
-
-
-/* Exception */
-
-static PyObject *StructError;
-
+#define PyStruct_Check(op) PyObject_TypeCheck(op, \
+            (PyTypeObject *)_structstate_global->PyStructType)
+#define PyStruct_CheckExact(op) (Py_TYPE(op) == \
+            (PyTypeObject *)_structstate_global->PyStructType)
 
 /* Define various structs to figure out the alignments of types */
 
@@ -105,7 +140,7 @@
                 return NULL;
         }
         else {
-            PyErr_SetString(StructError,
+            PyErr_SetString(_structstate_global->StructError,
                             "required argument is not an integer");
             return NULL;
         }
@@ -133,7 +168,7 @@
     Py_DECREF(v);
     if (x == (long)-1 && PyErr_Occurred()) {
         if (PyErr_ExceptionMatches(PyExc_OverflowError))
-            PyErr_SetString(StructError,
+            PyErr_SetString(_structstate_global->StructError,
                             "argument out of range");
         return -1;
     }
@@ -157,7 +192,7 @@
     Py_DECREF(v);
     if (x == (unsigned long)-1 && PyErr_Occurred()) {
         if (PyErr_ExceptionMatches(PyExc_OverflowError))
-            PyErr_SetString(StructError,
+            PyErr_SetString(_structstate_global->StructError,
                             "argument out of range");
         return -1;
     }
@@ -182,7 +217,7 @@
     Py_DECREF(v);
     if (x == (PY_LONG_LONG)-1 && PyErr_Occurred()) {
         if (PyErr_ExceptionMatches(PyExc_OverflowError))
-            PyErr_SetString(StructError,
+            PyErr_SetString(_structstate_global->StructError,
                             "argument out of range");
         return -1;
     }
@@ -205,7 +240,7 @@
     Py_DECREF(v);
     if (x == (unsigned PY_LONG_LONG)-1 && PyErr_Occurred()) {
         if (PyErr_ExceptionMatches(PyExc_OverflowError))
-            PyErr_SetString(StructError,
+            PyErr_SetString(_structstate_global->StructError,
                             "argument out of range");
         return -1;
     }
@@ -230,7 +265,7 @@
     Py_DECREF(v);
     if (x == (Py_ssize_t)-1 && PyErr_Occurred()) {
         if (PyErr_ExceptionMatches(PyExc_OverflowError))
-            PyErr_SetString(StructError,
+            PyErr_SetString(_structstate_global->StructError,
                             "argument out of range");
         return -1;
     }
@@ -253,7 +288,7 @@
     Py_DECREF(v);
     if (x == (size_t)-1 && PyErr_Occurred()) {
         if (PyErr_ExceptionMatches(PyExc_OverflowError))
-            PyErr_SetString(StructError,
+            PyErr_SetString(_structstate_global->StructError,
                             "argument out of range");
         return -1;
     }
@@ -306,13 +341,13 @@
     const size_t ulargest = (size_t)-1 >> ((SIZEOF_SIZE_T - f->size)*8);
     assert(f->size >= 1 && f->size <= SIZEOF_SIZE_T);
     if (is_unsigned)
-        PyErr_Format(StructError,
+        PyErr_Format(_structstate_global->StructError,
             "'%c' format requires 0 <= number <= %zu",
             f->format,
             ulargest);
     else {
         const Py_ssize_t largest = (Py_ssize_t)(ulargest >> 1);
-        PyErr_Format(StructError,
+        PyErr_Format(_structstate_global->StructError,
             "'%c' format requires %zd <= number <= %zd",
             f->format,
             ~ largest,
@@ -501,7 +536,7 @@
     if (get_long(v, &x) < 0)
         return -1;
     if (x < -128 || x > 127){
-        PyErr_SetString(StructError,
+        PyErr_SetString(_structstate_global->StructError,
                         "byte format requires -128 <= number <= 127");
         return -1;
     }
@@ -516,7 +551,7 @@
     if (get_long(v, &x) < 0)
         return -1;
     if (x < 0 || x > 255){
-        PyErr_SetString(StructError,
+        PyErr_SetString(_structstate_global->StructError,
                         "ubyte format requires 0 <= number <= 255");
         return -1;
     }
@@ -528,7 +563,7 @@
 np_char(char *p, PyObject *v, const formatdef *f)
 {
     if (!PyBytes_Check(v) || PyBytes_Size(v) != 1) {
-        PyErr_SetString(StructError,
+        PyErr_SetString(_structstate_global->StructError,
                         "char format requires a bytes object of length 1");
         return -1;
     }
@@ -544,7 +579,7 @@
     if (get_long(v, &x) < 0)
         return -1;
     if (x < SHRT_MIN || x > SHRT_MAX){
-        PyErr_SetString(StructError,
+        PyErr_SetString(_structstate_global->StructError,
                         "short format requires " STRINGIFY(SHRT_MIN)
                         " <= number <= " STRINGIFY(SHRT_MAX));
         return -1;
@@ -562,7 +597,7 @@
     if (get_long(v, &x) < 0)
         return -1;
     if (x < 0 || x > USHRT_MAX){
-        PyErr_SetString(StructError,
+        PyErr_SetString(_structstate_global->StructError,
                         "ushort format requires 0 <= number <= " STRINGIFY(USHRT_MAX));
         return -1;
     }
@@ -685,7 +720,7 @@
 {
     float x = (float)PyFloat_AsDouble(v);
     if (x == -1 && PyErr_Occurred()) {
-        PyErr_SetString(StructError,
+        PyErr_SetString(_structstate_global->StructError,
                         "required argument is not a float");
         return -1;
     }
@@ -698,7 +733,7 @@
 {
     double x = PyFloat_AsDouble(v);
     if (x == -1 && PyErr_Occurred()) {
-        PyErr_SetString(StructError,
+        PyErr_SetString(_structstate_global->StructError,
                         "required argument is not a float");
         return -1;
     }
@@ -926,7 +961,7 @@
 {
     double x = PyFloat_AsDouble(v);
     if (x == -1 && PyErr_Occurred()) {
-        PyErr_SetString(StructError,
+        PyErr_SetString(_structstate_global->StructError,
                         "required argument is not a float");
         return -1;
     }
@@ -938,7 +973,7 @@
 {
     double x = PyFloat_AsDouble(v);
     if (x == -1 && PyErr_Occurred()) {
-        PyErr_SetString(StructError,
+        PyErr_SetString(_structstate_global->StructError,
                         "required argument is not a float");
         return -1;
     }
@@ -1146,7 +1181,7 @@
 {
     double x = PyFloat_AsDouble(v);
     if (x == -1 && PyErr_Occurred()) {
-        PyErr_SetString(StructError,
+        PyErr_SetString(_structstate_global->StructError,
                         "required argument is not a float");
         return -1;
     }
@@ -1158,7 +1193,7 @@
 {
     double x = PyFloat_AsDouble(v);
     if (x == -1 && PyErr_Occurred()) {
-        PyErr_SetString(StructError,
+        PyErr_SetString(_structstate_global->StructError,
                         "required argument is not a float");
         return -1;
     }
@@ -1225,7 +1260,7 @@
             return f;
         }
     }
-    PyErr_SetString(StructError, "bad char in struct format");
+    PyErr_SetString(_structstate_global->StructError, "bad char in struct format");
     return NULL;
 }
 
@@ -1285,7 +1320,7 @@
                 num = num*10 + (c - '0');
             }
             if (c == '\0') {
-                PyErr_SetString(StructError,
+                PyErr_SetString(_structstate_global->StructError,
                                 "repeat count given without format specifier");
                 return -1;
             }
@@ -1376,7 +1411,7 @@
     return 0;
 
   overflow:
-    PyErr_SetString(StructError,
+    PyErr_SetString(_structstate_global->StructError,
                     "total struct size too long");
     return -1;
 }
@@ -1442,13 +1477,17 @@
 static void
 s_dealloc(PyStructObject *s)
 {
+    PyTypeObject *type = Py_TYPE(s);
     if (s->weakreflist != NULL)
         PyObject_ClearWeakRefs((PyObject *)s);
     if (s->s_codes != NULL) {
         PyMem_FREE(s->s_codes);
     }
     Py_XDECREF(s->s_format);
-    Py_TYPE(s)->tp_free((PyObject *)s);
+    type->tp_free((PyObject *)s);
+    if((void *)type->tp_dealloc == (void *)s_dealloc) {
+       Py_DECREF(type);
+    }
 }
 
 static PyObject *
@@ -1504,7 +1543,7 @@
     if (PyObject_GetBuffer(input, &vbuf, PyBUF_SIMPLE) < 0)
         return NULL;
     if (vbuf.len != soself->s_size) {
-        PyErr_Format(StructError,
+        PyErr_Format(_structstate_global->StructError,
                      "unpack requires a bytes object of length %zd",
                      soself->s_size);
         PyBuffer_Release(&vbuf);
@@ -1545,7 +1584,7 @@
     if (offset < 0)
         offset += vbuf.len;
     if (offset < 0 || vbuf.len - offset < soself->s_size) {
-        PyErr_Format(StructError,
+        PyErr_Format(_structstate_global->StructError,
             "unpack_from requires a buffer of at least %zd bytes",
             soself->s_size);
         PyBuffer_Release(&vbuf);
@@ -1587,7 +1626,7 @@
             void *p;
             isstring = PyBytes_Check(v);
             if (!isstring && !PyByteArray_Check(v)) {
-                PyErr_SetString(StructError,
+                PyErr_SetString(_structstate_global->StructError,
                                 "argument for 's' must be a bytes object");
                 return -1;
             }
@@ -1608,7 +1647,7 @@
             void *p;
             isstring = PyBytes_Check(v);
             if (!isstring && !PyByteArray_Check(v)) {
-                PyErr_SetString(StructError,
+                PyErr_SetString(_structstate_global->StructError,
                                 "argument for 'p' must be a bytes object");
                 return -1;
             }
@@ -1630,7 +1669,7 @@
         } else {
             if (e->pack(res, v, e) < 0) {
                 if (PyLong_Check(v) && PyErr_ExceptionMatches(PyExc_OverflowError))
-                    PyErr_SetString(StructError,
+                    PyErr_SetString(_structstate_global->StructError,
                                     "long too large to convert to int");
                 return -1;
             }
@@ -1661,7 +1700,7 @@
     assert(soself->s_codes != NULL);
     if (PyTuple_GET_SIZE(args) != soself->s_len)
     {
-        PyErr_Format(StructError,
+        PyErr_Format(_structstate_global->StructError,
             "pack requires exactly %zd arguments", soself->s_len);
         return NULL;
     }
@@ -1701,7 +1740,7 @@
     assert(soself->s_codes != NULL);
     if (PyTuple_GET_SIZE(args) != (soself->s_len + 2))
     {
-        PyErr_Format(StructError,
+        PyErr_Format(_structstate_global->StructError,
                      "pack_into requires exactly %zd arguments",
                      (soself->s_len + 2));
         return NULL;
@@ -1725,7 +1764,7 @@
 
     /* Check boundaries */
     if (offset < 0 || (buffer_len - offset) < soself->s_size) {
-        PyErr_Format(StructError,
+        PyErr_Format(_structstate_global->StructError,
                      "pack_into requires a buffer of at least %zd bytes",
                      soself->s_size);
         return NULL;
@@ -1790,78 +1829,59 @@
     {NULL} /* sentinel */
 };
 
-static
-PyTypeObject PyStructType = {
-    PyVarObject_HEAD_INIT(NULL, 0)
+static PyType_Slot PyStructType_slots[] = {
+    {Py_tp_dealloc, (destructor)s_dealloc},
+    {Py_tp_getattro, PyObject_GenericGetAttr},
+    {Py_tp_setattro, PyObject_GenericSetAttr},
+    {Py_tp_doc, s__doc__},
+    {Py_tp_methods, s_methods},
+    {Py_tp_members, NULL},
+    {Py_tp_getset, s_getsetlist},
+    {Py_tp_init, s_init},
+    {Py_tp_alloc, PyType_GenericAlloc},
+    {Py_tp_new, s_new},
+    {Py_tp_free, PyObject_Del},
+    {0, 0}
+};
+
+static PyType_Spec PyStructType_spec = {
     "Struct",
     sizeof(PyStructObject),
     0,
-    (destructor)s_dealloc,      /* tp_dealloc */
-    0,                                          /* tp_print */
-    0,                                          /* tp_getattr */
-    0,                                          /* tp_setattr */
-    0,                                          /* tp_reserved */
-    0,                                          /* tp_repr */
-    0,                                          /* tp_as_number */
-    0,                                          /* tp_as_sequence */
-    0,                                          /* tp_as_mapping */
-    0,                                          /* tp_hash */
-    0,                                          /* tp_call */
-    0,                                          /* tp_str */
-    PyObject_GenericGetAttr,            /* tp_getattro */
-    PyObject_GenericSetAttr,            /* tp_setattro */
-    0,                                          /* tp_as_buffer */
-    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /* tp_flags */
-    s__doc__,                           /* tp_doc */
-    0,                                          /* tp_traverse */
-    0,                                          /* tp_clear */
-    0,                                          /* tp_richcompare */
-    offsetof(PyStructObject, weakreflist),      /* tp_weaklistoffset */
-    0,                                          /* tp_iter */
-    0,                                          /* tp_iternext */
-    s_methods,                          /* tp_methods */
-    NULL,                               /* tp_members */
-    s_getsetlist,               /* tp_getset */
-    0,                                          /* tp_base */
-    0,                                          /* tp_dict */
-    0,                                          /* tp_descr_get */
-    0,                                          /* tp_descr_set */
-    0,                                          /* tp_dictoffset */
-    s_init,                             /* tp_init */
-    PyType_GenericAlloc,/* tp_alloc */
-    s_new,                              /* tp_new */
-    PyObject_Del,               /* tp_free */
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
+    PyStructType_slots,
 };
 
 
+
 /* ---- Standalone functions  ---- */
 
 #define MAXCACHE 100
-static PyObject *cache = NULL;
+
 
 static PyObject *
 cache_struct(PyObject *fmt)
 {
     PyObject * s_object;
 
-    if (cache == NULL) {
-        cache = PyDict_New();
-        if (cache == NULL)
+    if (_structstate_global->cache == NULL) {
+        _structstate_global->cache = PyDict_New();
+        if (_structstate_global->cache == NULL)
             return NULL;
     }
 
-    s_object = PyDict_GetItem(cache, fmt);
+    s_object = PyDict_GetItem(_structstate_global->cache, fmt);
     if (s_object != NULL) {
         Py_INCREF(s_object);
         return s_object;
     }
 
-    s_object = PyObject_CallFunctionObjArgs((PyObject *)(&PyStructType), fmt, NULL);
+    s_object = PyObject_CallFunctionObjArgs(_structstate_global->PyStructType, fmt, NULL);
     if (s_object != NULL) {
-        if (PyDict_Size(cache) >= MAXCACHE)
-            PyDict_Clear(cache);
+        if (PyDict_Size(_structstate_global->cache) >= MAXCACHE)
+            PyDict_Clear(_structstate_global->cache);
         /* Attempt to cache the result */
-        if (PyDict_SetItem(cache, fmt, s_object) == -1)
+        if (PyDict_SetItem(_structstate_global->cache, fmt, s_object) == -1)
             PyErr_Clear();
     }
     return s_object;
@@ -1873,7 +1893,7 @@
 static PyObject *
 clearcache(PyObject *self)
 {
-    Py_CLEAR(cache);
+    Py_CLEAR(_structstate_global->cache);
     Py_RETURN_NONE;
 }
 
@@ -2065,25 +2085,31 @@
     PyModuleDef_HEAD_INIT,
     "_struct",
     module_doc,
-    -1,
+    sizeof(_structstate),
     module_functions,
     NULL,
-    NULL,
-    NULL,
-    NULL
+    _struct_traverse,
+    _struct_clear,
+    _struct_free
 };
 
 PyMODINIT_FUNC
 PyInit__struct(void)
 {
     PyObject *m;
+    _structstate *state;
 
     m = PyModule_Create(&_structmodule);
     if (m == NULL)
         return NULL;
 
-    Py_TYPE(&PyStructType) = &PyType_Type;
-    if (PyType_Ready(&PyStructType) < 0)
+    state = _struct_state(m);
+
+    state->PyStructType = PyType_FromSpec(&PyStructType_spec);
+    ((PyTypeObject *)(state->PyStructType))->tp_weaklistoffset =
+                                        offsetof(PyStructObject, weakreflist);
+    Py_TYPE(state->PyStructType) = &PyType_Type;
+    if (state->PyStructType == NULL)
         return NULL;
 
     /* Check endian and swap in faster functions */
@@ -2126,17 +2152,17 @@
     }
 
     /* Add some symbolic constants to the module */
-    if (StructError == NULL) {
-        StructError = PyErr_NewException("struct.error", NULL, NULL);
-        if (StructError == NULL)
+    if (state->StructError == NULL) {
+        state->StructError = PyErr_NewException("struct.error", NULL, NULL);
+        if (state->StructError == NULL)
             return NULL;
     }
 
-    Py_INCREF(StructError);
-    PyModule_AddObject(m, "error", StructError);
+    Py_INCREF(state->StructError);
+    PyModule_AddObject(m, "error", state->StructError);
 
-    Py_INCREF((PyObject*)&PyStructType);
-    PyModule_AddObject(m, "Struct", (PyObject*)&PyStructType);
+    Py_INCREF(state->PyStructType);
+    PyModule_AddObject(m, "Struct", state->PyStructType);
 
     return m;
 }