Issue #18112: PEP 442 implementation (safe object finalization).

4 files changed, 163 insertions, 64 deletions

diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index 6a885cf..6fe5d58 100644
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -190,7 +190,8 @@ PyTypeObject PyBufferedIOBase_Type = {
     0,                          /*tp_getattro*/
     0,                          /*tp_setattro*/
     0,                          /*tp_as_buffer*/
-    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
+        | Py_TPFLAGS_HAVE_FINALIZE,  /*tp_flags*/
     bufferediobase_doc,         /* tp_doc */
     0,                          /* tp_traverse */
     0,                          /* tp_clear */
@@ -209,6 +210,16 @@ PyTypeObject PyBufferedIOBase_Type = {
     0,                          /* tp_init */
     0,                          /* tp_alloc */
     0,                          /* tp_new */
+    0,                          /* tp_free */
+    0,                          /* tp_is_gc */
+    0,                          /* tp_bases */
+    0,                          /* tp_mro */
+    0,                          /* tp_cache */
+    0,                          /* tp_subclasses */
+    0,                          /* tp_weaklist */
+    0,                          /* tp_del */
+    0,                          /* tp_version_tag */
+    0,                          /* tp_finalize */
 };
 
 
@@ -220,7 +231,7 @@ typedef struct {
     int detached;
     int readable;
     int writable;
-    int deallocating;
+    char finalizing;
 
     /* True if this is a vanilla Buffered object (rather than a user derived
        class) *and* the raw stream is a vanilla FileIO object. */
@@ -384,8 +395,8 @@ _enter_buffered_busy(buffered *self)
 static void
 buffered_dealloc(buffered *self)
 {
-    self->deallocating = 1;
-    if (self->ok && _PyIOBase_finalize((PyObject *) self) < 0)
+    self->finalizing = 1;
+    if (_PyIOBase_finalize((PyObject *) self) < 0)
         return;
     _PyObject_GC_UNTRACK(self);
     self->ok = 0;
@@ -428,8 +439,6 @@ buffered_traverse(buffered *self, visitproc visit, void *arg)
 static int
 buffered_clear(buffered *self)
 {
-    if (self->ok && _PyIOBase_finalize((PyObject *) self) < 0)
-        return -1;
     self->ok = 0;
     Py_CLEAR(self->raw);
     Py_CLEAR(self->dict);
@@ -508,7 +517,7 @@ buffered_close(buffered *self, PyObject *args)
         goto end;
     }
 
-    if (self->deallocating) {
+    if (self->finalizing) {
         PyObject *r = buffered_dealloc_warn(self, (PyObject *) self);
         if (r)
             Py_DECREF(r);
@@ -1749,6 +1758,7 @@ static PyMethodDef bufferedreader_methods[] = {
 
 static PyMemberDef bufferedreader_members[] = {
     {"raw", T_OBJECT, offsetof(buffered, raw), READONLY},
+    {"_finalizing", T_BOOL, offsetof(buffered, finalizing), 0},
     {NULL}
 };
 
@@ -1781,7 +1791,7 @@ PyTypeObject PyBufferedReader_Type = {
     0,                          /*tp_setattro*/
     0,                          /*tp_as_buffer*/
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
-            | Py_TPFLAGS_HAVE_GC, /*tp_flags*/
+        | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
     bufferedreader_doc,         /* tp_doc */
     (traverseproc)buffered_traverse, /* tp_traverse */
     (inquiry)buffered_clear,    /* tp_clear */
@@ -1800,6 +1810,16 @@ PyTypeObject PyBufferedReader_Type = {
     (initproc)bufferedreader_init, /* tp_init */
     0,                          /* tp_alloc */
     PyType_GenericNew,          /* tp_new */
+    0,                          /* tp_free */
+    0,                          /* tp_is_gc */
+    0,                          /* tp_bases */
+    0,                          /* tp_mro */
+    0,                          /* tp_cache */
+    0,                          /* tp_subclasses */
+    0,                          /* tp_weaklist */
+    0,                          /* tp_del */
+    0,                          /* tp_version_tag */
+    0,                          /* tp_finalize */
 };
 
 
@@ -2130,6 +2150,7 @@ static PyMethodDef bufferedwriter_methods[] = {
 
 static PyMemberDef bufferedwriter_members[] = {
     {"raw", T_OBJECT, offsetof(buffered, raw), READONLY},
+    {"_finalizing", T_BOOL, offsetof(buffered, finalizing), 0},
     {NULL}
 };
 
@@ -2162,7 +2183,7 @@ PyTypeObject PyBufferedWriter_Type = {
     0,                          /*tp_setattro*/
     0,                          /*tp_as_buffer*/
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
-        | Py_TPFLAGS_HAVE_GC,   /*tp_flags*/
+        | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE,   /*tp_flags*/
     bufferedwriter_doc,         /* tp_doc */
     (traverseproc)buffered_traverse, /* tp_traverse */
     (inquiry)buffered_clear,    /* tp_clear */
@@ -2181,6 +2202,16 @@ PyTypeObject PyBufferedWriter_Type = {
     (initproc)bufferedwriter_init, /* tp_init */
     0,                          /* tp_alloc */
     PyType_GenericNew,          /* tp_new */
+    0,                          /* tp_free */
+    0,                          /* tp_is_gc */
+    0,                          /* tp_bases */
+    0,                          /* tp_mro */
+    0,                          /* tp_cache */
+    0,                          /* tp_subclasses */
+    0,                          /* tp_weaklist */
+    0,                          /* tp_del */
+    0,                          /* tp_version_tag */
+    0,                          /* tp_finalize */
 };
 
 
@@ -2416,7 +2447,7 @@ PyTypeObject PyBufferedRWPair_Type = {
     0,                          /*tp_setattro*/
     0,                          /*tp_as_buffer*/
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
-        | Py_TPFLAGS_HAVE_GC,   /* tp_flags */
+        | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE,   /* tp_flags */
     bufferedrwpair_doc,         /* tp_doc */
     (traverseproc)bufferedrwpair_traverse, /* tp_traverse */
     (inquiry)bufferedrwpair_clear, /* tp_clear */
@@ -2435,6 +2466,16 @@ PyTypeObject PyBufferedRWPair_Type = {
     (initproc)bufferedrwpair_init, /* tp_init */
     0,                          /* tp_alloc */
     PyType_GenericNew,          /* tp_new */
+    0,                          /* tp_free */
+    0,                          /* tp_is_gc */
+    0,                          /* tp_bases */
+    0,                          /* tp_mro */
+    0,                          /* tp_cache */
+    0,                          /* tp_subclasses */
+    0,                          /* tp_weaklist */
+    0,                          /* tp_del */
+    0,                          /* tp_version_tag */
+    0,                          /* tp_finalize */
 };
 
 
@@ -2522,6 +2563,7 @@ static PyMethodDef bufferedrandom_methods[] = {
 
 static PyMemberDef bufferedrandom_members[] = {
     {"raw", T_OBJECT, offsetof(buffered, raw), READONLY},
+    {"_finalizing", T_BOOL, offsetof(buffered, finalizing), 0},
     {NULL}
 };
 
@@ -2554,7 +2596,7 @@ PyTypeObject PyBufferedRandom_Type = {
     0,                          /*tp_setattro*/
     0,                          /*tp_as_buffer*/
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
-        | Py_TPFLAGS_HAVE_GC,   /*tp_flags*/
+        | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE,   /*tp_flags*/
     bufferedrandom_doc,         /* tp_doc */
     (traverseproc)buffered_traverse, /* tp_traverse */
     (inquiry)buffered_clear,    /* tp_clear */
@@ -2573,4 +2615,14 @@ PyTypeObject PyBufferedRandom_Type = {
     (initproc)bufferedrandom_init, /* tp_init */
     0,                          /* tp_alloc */
     PyType_GenericNew,          /* tp_new */
+    0,                          /* tp_free */
+    0,                          /* tp_is_gc */
+    0,                          /* tp_bases */
+    0,                          /* tp_mro */
+    0,                          /* tp_cache */
+    0,                          /* tp_subclasses */
+    0,                          /* tp_weaklist */
+    0,                          /* tp_del */
+    0,                          /* tp_version_tag */
+    0,                          /* tp_finalize */
 };
diff --git a/Modules/_io/fileio.c b/Modules/_io/fileio.c
index 5280991..e88ae87 100644
--- a/Modules/_io/fileio.c
+++ b/Modules/_io/fileio.c
@@ -51,7 +51,7 @@ typedef struct {
     unsigned int writable : 1;
     signed int seekable : 2; /* -1 means unknown */
     unsigned int closefd : 1;
-    unsigned int deallocating: 1;
+    char finalizing;
     PyObject *weakreflist;
     PyObject *dict;
 } fileio;
@@ -128,7 +128,7 @@ fileio_close(fileio *self)
         self->fd = -1;
         Py_RETURN_NONE;
     }
-    if (self->deallocating) {
+    if (self->finalizing) {
         PyObject *r = fileio_dealloc_warn(self, (PyObject *) self);
         if (r)
             Py_DECREF(r);
@@ -447,7 +447,7 @@ fileio_clear(fileio *self)
 static void
 fileio_dealloc(fileio *self)
 {
-    self->deallocating = 1;
+    self->finalizing = 1;
     if (_PyIOBase_finalize((PyObject *) self) < 0)
         return;
     _PyObject_GC_UNTRACK(self);
@@ -1182,6 +1182,11 @@ static PyGetSetDef fileio_getsetlist[] = {
     {NULL},
 };
 
+static PyMemberDef fileio_members[] = {
+    {"_finalizing", T_BOOL, offsetof(fileio, finalizing), 0},
+    {NULL}
+};
+
 PyTypeObject PyFileIO_Type = {
     PyVarObject_HEAD_INIT(NULL, 0)
     "_io.FileIO",
@@ -1203,7 +1208,7 @@ PyTypeObject PyFileIO_Type = {
     0,                                          /* tp_setattro */
     0,                                          /* tp_as_buffer */
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
-                    | Py_TPFLAGS_HAVE_GC,       /* tp_flags */
+        | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE,       /* tp_flags */
     fileio_doc,                                 /* tp_doc */
     (traverseproc)fileio_traverse,              /* tp_traverse */
     (inquiry)fileio_clear,                      /* tp_clear */
@@ -1212,7 +1217,7 @@ PyTypeObject PyFileIO_Type = {
     0,                                          /* tp_iter */
     0,                                          /* tp_iternext */
     fileio_methods,                             /* tp_methods */
-    0,                                          /* tp_members */
+    fileio_members,                             /* tp_members */
     fileio_getsetlist,                          /* tp_getset */
     0,                                          /* tp_base */
     0,                                          /* tp_dict */
@@ -1223,4 +1228,13 @@ PyTypeObject PyFileIO_Type = {
     PyType_GenericAlloc,                        /* tp_alloc */
     fileio_new,                                 /* tp_new */
     PyObject_GC_Del,                            /* tp_free */
+    0,                                          /* tp_is_gc */
+    0,                                          /* tp_bases */
+    0,                                          /* tp_mro */
+    0,                                          /* tp_cache */
+    0,                                          /* tp_subclasses */
+    0,                                          /* tp_weaklist */
+    0,                                          /* tp_del */
+    0,                                          /* tp_version_tag */
+    0,                                          /* tp_finalize */
 };
diff --git a/Modules/_io/iobase.c b/Modules/_io/iobase.c
index e38473a..a4f2c0e 100644
--- a/Modules/_io/iobase.c
+++ b/Modules/_io/iobase.c
@@ -196,21 +196,17 @@ iobase_close(PyObject *self, PyObject *args)
 
 /* Finalization and garbage collection support */
 
-int
-_PyIOBase_finalize(PyObject *self)
+static void
+iobase_finalize(PyObject *self)
 {
     PyObject *res;
-    PyObject *tp, *v, *tb;
-    int closed = 1;
-    int is_zombie;
+    PyObject *error_type, *error_value, *error_traceback;
+    int closed;
+    _Py_IDENTIFIER(_finalizing);
+
+    /* Save the current exception, if any. */
+    PyErr_Fetch(&error_type, &error_value, &error_traceback);
 
-    /* If _PyIOBase_finalize() is called from a destructor, we need to
-       resurrect the object as calling close() can invoke arbitrary code. */
-    is_zombie = (Py_REFCNT(self) == 0);
-    if (is_zombie) {
-        ++Py_REFCNT(self);
-    }
-    PyErr_Fetch(&tp, &v, &tb);
     /* If `closed` doesn't exist or can't be evaluated as bool, then the
        object is probably in an unusable state, so ignore. */
     res = PyObject_GetAttr(self, _PyIO_str_closed);
@@ -223,6 +219,10 @@ _PyIOBase_finalize(PyObject *self)
             PyErr_Clear();
     }
     if (closed == 0) {
+        /* Signal close() that it was called as part of the object
+           finalization process. */
+        if (_PyObject_SetAttrId(self, &PyId__finalizing, Py_True))
+            PyErr_Clear();
         res = PyObject_CallMethodObjArgs((PyObject *) self, _PyIO_str_close,
                                           NULL);
         /* Silencing I/O errors is bad, but printing spurious tracebacks is
@@ -233,31 +233,25 @@ _PyIOBase_finalize(PyObject *self)
         else
             Py_DECREF(res);
     }
-    PyErr_Restore(tp, v, tb);
-    if (is_zombie) {
-        if (--Py_REFCNT(self) != 0) {
-            /* The object lives again. The following code is taken from
-               slot_tp_del in typeobject.c. */
-            Py_ssize_t refcnt = Py_REFCNT(self);
-            _Py_NewReference(self);
-            Py_REFCNT(self) = refcnt;
-            /* If Py_REF_DEBUG, _Py_NewReference bumped _Py_RefTotal, so
-             * we need to undo that. */
-            _Py_DEC_REFTOTAL;
-            /* If Py_TRACE_REFS, _Py_NewReference re-added self to the object
-             * chain, so no more to do there.
-             * If COUNT_ALLOCS, the original decref bumped tp_frees, and
-             * _Py_NewReference bumped tp_allocs:  both of those need to be
-             * undone.
-             */
-#ifdef COUNT_ALLOCS
-            --Py_TYPE(self)->tp_frees;
-            --Py_TYPE(self)->tp_allocs;
-#endif
-            return -1;
-        }
+
+    /* Restore the saved exception. */
+    PyErr_Restore(error_type, error_value, error_traceback);
+}
+
+int
+_PyIOBase_finalize(PyObject *self)
+{
+    int is_zombie;
+
+    /* If _PyIOBase_finalize() is called from a destructor, we need to
+       resurrect the object as calling close() can invoke arbitrary code. */
+    is_zombie = (Py_REFCNT(self) == 0);
+    if (is_zombie)
+        return PyObject_CallFinalizerFromDealloc(self);
+    else {
+        PyObject_CallFinalizer(self);
+        return 0;
     }
-    return 0;
 }
 
 static int
@@ -270,8 +264,6 @@ iobase_traverse(iobase *self, visitproc visit, void *arg)
 static int
 iobase_clear(iobase *self)
 {
-    if (_PyIOBase_finalize((PyObject *) self) < 0)
-        return -1;
     Py_CLEAR(self->dict);
     return 0;
 }
@@ -741,7 +733,7 @@ PyTypeObject PyIOBase_Type = {
     0,                          /*tp_setattro*/
     0,                          /*tp_as_buffer*/
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
-        | Py_TPFLAGS_HAVE_GC,   /*tp_flags*/
+        | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE,   /*tp_flags*/
     iobase_doc,                 /* tp_doc */
     (traverseproc)iobase_traverse, /* tp_traverse */
     (inquiry)iobase_clear,      /* tp_clear */
@@ -760,6 +752,16 @@ PyTypeObject PyIOBase_Type = {
     0,                          /* tp_init */
     0,                          /* tp_alloc */
     PyType_GenericNew,          /* tp_new */
+    0,                          /* tp_free */
+    0,                          /* tp_is_gc */
+    0,                          /* tp_bases */
+    0,                          /* tp_mro */
+    0,                          /* tp_cache */
+    0,                          /* tp_subclasses */
+    0,                          /* tp_weaklist */
+    0,                          /* tp_del */
+    0,                          /* tp_version_tag */
+    (destructor)iobase_finalize, /* tp_finalize */
 };
 
 
@@ -905,7 +907,7 @@ PyTypeObject PyRawIOBase_Type = {
     0,                          /*tp_getattro*/
     0,                          /*tp_setattro*/
     0,                          /*tp_as_buffer*/
-    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_FINALIZE,  /*tp_flags*/
     rawiobase_doc,              /* tp_doc */
     0,                          /* tp_traverse */
     0,                          /* tp_clear */
@@ -924,4 +926,14 @@ PyTypeObject PyRawIOBase_Type = {
     0,                          /* tp_init */
     0,                          /* tp_alloc */
     0,                          /* tp_new */
+    0,                          /* tp_free */
+    0,                          /* tp_is_gc */
+    0,                          /* tp_bases */
+    0,                          /* tp_mro */
+    0,                          /* tp_cache */
+    0,                          /* tp_subclasses */
+    0,                          /* tp_weaklist */
+    0,                          /* tp_del */
+    0,                          /* tp_version_tag */
+    0,                          /* tp_finalize */
 };
diff --git a/Modules/_io/textio.c b/Modules/_io/textio.c
index 283411b..5d2438d 100644
--- a/Modules/_io/textio.c
+++ b/Modules/_io/textio.c
@@ -173,7 +173,8 @@ PyTypeObject PyTextIOBase_Type = {
     0,                          /*tp_getattro*/
     0,                          /*tp_setattro*/
     0,                          /*tp_as_buffer*/
-    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,  /*tp_flags*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
+        | Py_TPFLAGS_HAVE_FINALIZE,  /*tp_flags*/
     textiobase_doc,             /* tp_doc */
     0,                          /* tp_traverse */
     0,                          /* tp_clear */
@@ -192,6 +193,16 @@ PyTypeObject PyTextIOBase_Type = {
     0,                          /* tp_init */
     0,                          /* tp_alloc */
     0,                          /* tp_new */
+    0,                          /* tp_free */
+    0,                          /* tp_is_gc */
+    0,                          /* tp_bases */
+    0,                          /* tp_mro */
+    0,                          /* tp_cache */
+    0,                          /* tp_subclasses */
+    0,                          /* tp_weaklist */
+    0,                          /* tp_del */
+    0,                          /* tp_version_tag */
+    0,                          /* tp_finalize */
 };
 
 
@@ -691,7 +702,7 @@ typedef struct
     char seekable;
     char has_read1;
     char telling;
-    char deallocating;
+    char finalizing;
     /* Specialized encoding func (see below) */
     encodefunc_t encodefunc;
     /* Whether or not it's the start of the stream */
@@ -1112,8 +1123,6 @@ textiowrapper_init(textio *self, PyObject *args, PyObject *kwds)
 static int
 _textiowrapper_clear(textio *self)
 {
-    if (self->ok && _PyIOBase_finalize((PyObject *) self) < 0)
-        return -1;
     self->ok = 0;
     Py_CLEAR(self->buffer);
     Py_CLEAR(self->encoding);
@@ -1131,9 +1140,10 @@ _textiowrapper_clear(textio *self)
 static void
 textiowrapper_dealloc(textio *self)
 {
-    self->deallocating = 1;
-    if (_textiowrapper_clear(self) < 0)
+    self->finalizing = 1;
+    if (_PyIOBase_finalize((PyObject *) self) < 0)
         return;
+    _textiowrapper_clear(self);
     _PyObject_GC_UNTRACK(self);
     if (self->weakreflist != NULL)
         PyObject_ClearWeakRefs((PyObject *)self);
@@ -2573,7 +2583,7 @@ textiowrapper_close(textio *self, PyObject *args)
     }
     else {
         PyObject *exc = NULL, *val, *tb;
-        if (self->deallocating) {
+        if (self->finalizing) {
             res = _PyObject_CallMethodId(self->buffer, &PyId__dealloc_warn, "O", self);
             if (res)
                 Py_DECREF(res);
@@ -2734,6 +2744,7 @@ static PyMemberDef textiowrapper_members[] = {
     {"encoding", T_OBJECT, offsetof(textio, encoding), READONLY},
     {"buffer", T_OBJECT, offsetof(textio, buffer), READONLY},
     {"line_buffering", T_BOOL, offsetof(textio, line_buffering), READONLY},
+    {"_finalizing", T_BOOL, offsetof(textio, finalizing), 0},
     {NULL}
 };
 
@@ -2770,7 +2781,7 @@ PyTypeObject PyTextIOWrapper_Type = {
     0,                          /*tp_setattro*/
     0,                          /*tp_as_buffer*/
     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE
-            | Py_TPFLAGS_HAVE_GC, /*tp_flags*/
+        | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_HAVE_FINALIZE, /*tp_flags*/
     textiowrapper_doc,          /* tp_doc */
     (traverseproc)textiowrapper_traverse, /* tp_traverse */
     (inquiry)textiowrapper_clear, /* tp_clear */
@@ -2789,4 +2800,14 @@ PyTypeObject PyTextIOWrapper_Type = {
     (initproc)textiowrapper_init, /* tp_init */
     0,                          /* tp_alloc */
     PyType_GenericNew,          /* tp_new */
+    0,                          /* tp_free */
+    0,                          /* tp_is_gc */
+    0,                          /* tp_bases */
+    0,                          /* tp_mro */
+    0,                          /* tp_cache */
+    0,                          /* tp_subclasses */
+    0,                          /* tp_weaklist */
+    0,                          /* tp_del */
+    0,                          /* tp_version_tag */
+    0,                          /* tp_finalize */
 };