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pythongh-108240: Add _PyCapsule_SetTraverse() interal function
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The _socket extension uses _PyCapsule_SetTraverse() to visit and clear
the socket type in the garbage collector. So the _socket.socket type
can be cleared in some corner cases when it wasn't possible before.
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@vstinner
vstinner committed Aug 23, 2023
1 parent ec3527d commit 70517e9
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Showing 3 changed files with 135 additions and 72 deletions.
4 changes: 4 additions & 0 deletions Include/pycapsule.h
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Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,10 @@ PyAPI_FUNC(int) PyCapsule_SetName(PyObject *capsule, const char *name);

PyAPI_FUNC(int) PyCapsule_SetContext(PyObject *capsule, void *context);

#ifdef Py_BUILD_CORE
PyAPI_FUNC(int) _PyCapsule_SetTraverse(PyObject *op, traverseproc traverse_func, inquiry clear_func);
#endif

PyAPI_FUNC(void *) PyCapsule_Import(
const char *name, /* UTF-8 encoded string */
int no_block);
Expand Down
37 changes: 31 additions & 6 deletions Modules/socketmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7314,20 +7314,39 @@ os_init(void)
}
#endif

static int
sock_capi_traverse(PyObject *capsule, visitproc visit, void *arg)
{
PySocketModule_APIObject *capi = PyCapsule_GetPointer(capsule, PySocket_CAPSULE_NAME);
assert(capi != NULL);
Py_VISIT(capi->Sock_Type);
return 0;
}

static int
sock_capi_clear(PyObject *capsule)
{
PySocketModule_APIObject *capi = PyCapsule_GetPointer(capsule, PySocket_CAPSULE_NAME);
assert(capi != NULL);
Py_CLEAR(capi->Sock_Type);
return 0;
}

static void
sock_free_api(PySocketModule_APIObject *capi)
sock_capi_free(PySocketModule_APIObject *capi)
{
Py_DECREF(capi->Sock_Type);
Py_XDECREF(capi->Sock_Type); // sock_capi_free() can clear it
Py_DECREF(capi->error);
Py_DECREF(capi->timeout_error);
PyMem_Free(capi);
}

static void
sock_destroy_api(PyObject *capsule)
sock_capi_destroy(PyObject *capsule)
{
void *capi = PyCapsule_GetPointer(capsule, PySocket_CAPSULE_NAME);
sock_free_api(capi);
assert(capi != NULL);
sock_capi_free(capi);
}

static PySocketModule_APIObject *
Expand Down Expand Up @@ -7432,11 +7451,17 @@ socket_exec(PyObject *m)
}
PyObject *capsule = PyCapsule_New(capi,
PySocket_CAPSULE_NAME,
sock_destroy_api);
sock_capi_destroy);
if (capsule == NULL) {
sock_free_api(capi);
sock_capi_free(capi);
goto error;
}
if (_PyCapsule_SetTraverse(capsule,
sock_capi_traverse, sock_capi_clear) < 0) {
sock_capi_free(capi);
goto error;
}

if (PyModule_Add(m, PySocket_CAPI_NAME, capsule) < 0) {
goto error;
}
Expand Down
166 changes: 100 additions & 66 deletions Objects/capsule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -9,18 +9,28 @@ typedef struct {
const char *name;
void *context;
PyCapsule_Destructor destructor;
traverseproc traverse_func;
inquiry clear_func;
} PyCapsule;



static int
_is_legal_capsule(PyCapsule *capsule, const char *invalid_capsule)
_is_legal_capsule(PyObject *op, const char *invalid_capsule)
{
if (!capsule || !PyCapsule_CheckExact(capsule) || capsule->pointer == NULL) {
PyErr_SetString(PyExc_ValueError, invalid_capsule);
return 0;
if (!op || !PyCapsule_CheckExact(op)) {
goto error;
}
PyCapsule *capsule = (PyCapsule *)op;

if (capsule->pointer == NULL) {
goto error;
}
return 1;

error:
PyErr_SetString(PyExc_ValueError, invalid_capsule);
return 0;
}

#define is_legal_capsule(capsule, name) \
Expand Down Expand Up @@ -50,7 +60,7 @@ PyCapsule_New(void *pointer, const char *name, PyCapsule_Destructor destructor)
return NULL;
}

capsule = PyObject_New(PyCapsule, &PyCapsule_Type);
capsule = PyObject_GC_New(PyCapsule, &PyCapsule_Type);
if (capsule == NULL) {
return NULL;
}
Expand All @@ -59,15 +69,18 @@ PyCapsule_New(void *pointer, const char *name, PyCapsule_Destructor destructor)
capsule->name = name;
capsule->context = NULL;
capsule->destructor = destructor;
capsule->traverse_func = NULL;
capsule->clear_func = NULL;
// Only track the capsule if _PyCapsule_SetTraverse() is called

return (PyObject *)capsule;
}


int
PyCapsule_IsValid(PyObject *o, const char *name)
PyCapsule_IsValid(PyObject *op, const char *name)
{
PyCapsule *capsule = (PyCapsule *)o;
PyCapsule *capsule = (PyCapsule *)op;

return (capsule != NULL &&
PyCapsule_CheckExact(capsule) &&
Expand All @@ -77,13 +90,12 @@ PyCapsule_IsValid(PyObject *o, const char *name)


void *
PyCapsule_GetPointer(PyObject *o, const char *name)
PyCapsule_GetPointer(PyObject *op, const char *name)
{
PyCapsule *capsule = (PyCapsule *)o;

if (!is_legal_capsule(capsule, "PyCapsule_GetPointer")) {
if (!is_legal_capsule(op, "PyCapsule_GetPointer")) {
return NULL;
}
PyCapsule *capsule = (PyCapsule *)op;

if (!name_matches(name, capsule->name)) {
PyErr_SetString(PyExc_ValueError, "PyCapsule_GetPointer called with incorrect name");
Expand All @@ -95,52 +107,48 @@ PyCapsule_GetPointer(PyObject *o, const char *name)


const char *
PyCapsule_GetName(PyObject *o)
PyCapsule_GetName(PyObject *op)
{
PyCapsule *capsule = (PyCapsule *)o;

if (!is_legal_capsule(capsule, "PyCapsule_GetName")) {
if (!is_legal_capsule(op, "PyCapsule_GetName")) {
return NULL;
}
PyCapsule *capsule = (PyCapsule *)op;
return capsule->name;
}


PyCapsule_Destructor
PyCapsule_GetDestructor(PyObject *o)
PyCapsule_GetDestructor(PyObject *op)
{
PyCapsule *capsule = (PyCapsule *)o;

if (!is_legal_capsule(capsule, "PyCapsule_GetDestructor")) {
if (!is_legal_capsule(op, "PyCapsule_GetDestructor")) {
return NULL;
}
PyCapsule *capsule = (PyCapsule *)op;
return capsule->destructor;
}


void *
PyCapsule_GetContext(PyObject *o)
PyCapsule_GetContext(PyObject *op)
{
PyCapsule *capsule = (PyCapsule *)o;

if (!is_legal_capsule(capsule, "PyCapsule_GetContext")) {
if (!is_legal_capsule(op, "PyCapsule_GetContext")) {
return NULL;
}
PyCapsule *capsule = (PyCapsule *)op;
return capsule->context;
}


int
PyCapsule_SetPointer(PyObject *o, void *pointer)
PyCapsule_SetPointer(PyObject *op, void *pointer)
{
PyCapsule *capsule = (PyCapsule *)o;

if (!pointer) {
PyErr_SetString(PyExc_ValueError, "PyCapsule_SetPointer called with null pointer");
if (!is_legal_capsule(op, "PyCapsule_SetPointer")) {
return -1;
}
PyCapsule *capsule = (PyCapsule *)op;

if (!is_legal_capsule(capsule, "PyCapsule_SetPointer")) {
if (!pointer) {
PyErr_SetString(PyExc_ValueError, "PyCapsule_SetPointer called with null pointer");
return -1;
}

Expand All @@ -150,47 +158,62 @@ PyCapsule_SetPointer(PyObject *o, void *pointer)


int
PyCapsule_SetName(PyObject *o, const char *name)
PyCapsule_SetName(PyObject *op, const char *name)
{
PyCapsule *capsule = (PyCapsule *)o;

if (!is_legal_capsule(capsule, "PyCapsule_SetName")) {
if (!is_legal_capsule(op, "PyCapsule_SetName")) {
return -1;
}
PyCapsule *capsule = (PyCapsule *)op;

capsule->name = name;
return 0;
}


int
PyCapsule_SetDestructor(PyObject *o, PyCapsule_Destructor destructor)
PyCapsule_SetDestructor(PyObject *op, PyCapsule_Destructor destructor)
{
PyCapsule *capsule = (PyCapsule *)o;

if (!is_legal_capsule(capsule, "PyCapsule_SetDestructor")) {
if (!is_legal_capsule(op, "PyCapsule_SetDestructor")) {
return -1;
}
PyCapsule *capsule = (PyCapsule *)op;

capsule->destructor = destructor;
return 0;
}


int
PyCapsule_SetContext(PyObject *o, void *context)
PyCapsule_SetContext(PyObject *op, void *context)
{
PyCapsule *capsule = (PyCapsule *)o;

if (!is_legal_capsule(capsule, "PyCapsule_SetContext")) {
if (!is_legal_capsule(op, "PyCapsule_SetContext")) {
return -1;
}
PyCapsule *capsule = (PyCapsule *)op;

capsule->context = context;
return 0;
}


int
_PyCapsule_SetTraverse(PyObject *op, traverseproc traverse_func, inquiry clear_func)
{
if (!is_legal_capsule(op, "_PyCapsule_SetTraverse")) {
return -1;
}
PyCapsule *capsule = (PyCapsule *)op;

if (!PyObject_GC_IsTracked(op)) {
PyObject_GC_Track(op);
}

capsule->traverse_func = traverse_func;
capsule->clear_func = clear_func;
return 0;
}


void *
PyCapsule_Import(const char *name, int no_block)
{
Expand Down Expand Up @@ -249,13 +272,14 @@ PyCapsule_Import(const char *name, int no_block)


static void
capsule_dealloc(PyObject *o)
capsule_dealloc(PyObject *op)
{
PyCapsule *capsule = (PyCapsule *)o;
PyCapsule *capsule = (PyCapsule *)op;
PyObject_GC_UnTrack(op);
if (capsule->destructor) {
capsule->destructor(o);
capsule->destructor(op);
}
PyObject_Free(o);
PyObject_GC_Del(op);
}


Expand All @@ -279,6 +303,29 @@ capsule_repr(PyObject *o)
}


static int
capsule_traverse(PyCapsule *capsule, visitproc visit, void *arg)
{
if (capsule->traverse_func) {
return capsule->traverse_func((PyObject*)capsule, visit, arg);
}
else {
return 0;
}
}


static int
capsule_clear(PyCapsule *capsule)
{
if (capsule->clear_func) {
return capsule->clear_func((PyObject*)capsule);
}
else {
return 0;
}
}


PyDoc_STRVAR(PyCapsule_Type__doc__,
"Capsule objects let you wrap a C \"void *\" pointer in a Python\n\
Expand All @@ -293,27 +340,14 @@ Python import mechanism to link to one another.\n\

PyTypeObject PyCapsule_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
"PyCapsule", /*tp_name*/
sizeof(PyCapsule), /*tp_basicsize*/
0, /*tp_itemsize*/
/* methods */
capsule_dealloc, /*tp_dealloc*/
0, /*tp_vectorcall_offset*/
0, /*tp_getattr*/
0, /*tp_setattr*/
0, /*tp_as_async*/
capsule_repr, /*tp_repr*/
0, /*tp_as_number*/
0, /*tp_as_sequence*/
0, /*tp_as_mapping*/
0, /*tp_hash*/
0, /*tp_call*/
0, /*tp_str*/
0, /*tp_getattro*/
0, /*tp_setattro*/
0, /*tp_as_buffer*/
0, /*tp_flags*/
PyCapsule_Type__doc__ /*tp_doc*/
.tp_name = "PyCapsule",
.tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
.tp_basicsize = sizeof(PyCapsule),
.tp_dealloc = capsule_dealloc,
.tp_repr = capsule_repr,
.tp_doc = PyCapsule_Type__doc__,
.tp_traverse = (traverseproc)capsule_traverse,
.tp_clear = (inquiry)capsule_clear,
};


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