bpo-1635741: Add PyModule_AddObjectRef() function (GH-23122)
Added PyModule_AddObjectRef() function: similar to PyModule_AddObjectRef() but don't steal a reference to the value on success.
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@ -264,7 +264,7 @@ of the following two module creation functions:
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instead; only use this if you are sure you need it.
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Before it is returned from in the initialization function, the resulting module
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object is typically populated using functions like :c:func:`PyModule_AddObject`.
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object is typically populated using functions like :c:func:`PyModule_AddObjectRef`.
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.. _multi-phase-initialization:
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@ -437,26 +437,102 @@ a function called from a module execution slot (if using multi-phase
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initialization), can use the following functions to help initialize the module
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state:
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.. c:function:: int PyModule_AddObjectRef(PyObject *module, const char *name, PyObject *value)
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Add an object to *module* as *name*. This is a convenience function which
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can be used from the module's initialization function.
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On success, return ``0``. On error, raise an exception and return ``-1``.
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Return ``NULL`` if *value* is ``NULL``. It must be called with an exception
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raised in this case.
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Example usage::
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static int
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add_spam(PyObject *module, int value)
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{
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PyObject *obj = PyLong_FromLong(value);
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if (obj == NULL) {
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return -1;
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}
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int res = PyModule_AddObjectRef(module, "spam", obj);
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Py_DECREF(obj);
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return res;
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}
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The example can also be written without checking explicitly if *obj* is
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``NULL``::
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static int
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add_spam(PyObject *module, int value)
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{
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PyObject *obj = PyLong_FromLong(value);
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int res = PyModule_AddObjectRef(module, "spam", obj);
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Py_XDECREF(obj);
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return res;
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}
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Note that ``Py_XDECREF()`` should be used instead of ``Py_DECREF()`` in
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this case, since *obj* can be ``NULL``.
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.. versionadded:: 3.10
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.. c:function:: int PyModule_AddObject(PyObject *module, const char *name, PyObject *value)
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Add an object to *module* as *name*. This is a convenience function which can
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be used from the module's initialization function. This steals a reference to
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*value* on success. Return ``-1`` on error, ``0`` on success.
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Similar to :c:func:`PyModule_AddObjectRef`, but steals a reference to
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*value* on success (if it returns ``0``).
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The new :c:func:`PyModule_AddObjectRef` function is recommended, since it is
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easy to introduce reference leaks by misusing the
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:c:func:`PyModule_AddObject` function.
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.. note::
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Unlike other functions that steal references, ``PyModule_AddObject()`` only
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decrements the reference count of *value* **on success**.
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Unlike other functions that steal references, ``PyModule_AddObject()``
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only decrements the reference count of *value* **on success**.
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This means that its return value must be checked, and calling code must
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:c:func:`Py_DECREF` *value* manually on error. Example usage::
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:c:func:`Py_DECREF` *value* manually on error.
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Example usage::
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static int
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add_spam(PyObject *module, int value)
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{
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PyObject *obj = PyLong_FromLong(value);
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if (obj == NULL) {
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return -1;
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}
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if (PyModule_AddObject(module, "spam", obj) < 0) {
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Py_DECREF(obj);
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return -1;
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}
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// PyModule_AddObject() stole a reference to obj:
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// Py_DECREF(obj) is not needed here
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return 0;
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}
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The example can also be written without checking explicitly if *obj* is
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``NULL``::
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static int
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add_spam(PyObject *module, int value)
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{
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PyObject *obj = PyLong_FromLong(value);
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if (PyModule_AddObject(module, "spam", obj) < 0) {
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Py_XDECREF(obj);
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return -1;
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}
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// PyModule_AddObject() stole a reference to obj:
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// Py_DECREF(obj) is not needed here
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return 0;
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}
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Note that ``Py_XDECREF()`` should be used instead of ``Py_DECREF()`` in
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this case, since *obj* can be ``NULL``.
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Py_INCREF(spam);
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if (PyModule_AddObject(module, "spam", spam) < 0) {
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Py_DECREF(module);
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Py_DECREF(spam);
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return NULL;
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}
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.. c:function:: int PyModule_AddIntConstant(PyObject *module, const char *name, long value)
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@ -374,6 +374,11 @@ New Features
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* Added :c:func:`PyUnicode_AsUTF8AndSize` to the limited C API.
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(Contributed by Alex Gaynor in :issue:`41784`.)
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* Added :c:func:`PyModule_AddObjectRef` function: similar to
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:c:func:`PyModule_AddObjectRef` but don't steal a reference to the value on
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success.
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(Contributed by Victor Stinner in :issue:`1635741`.)
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Porting to Python 3.10
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----------------------
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@ -136,7 +136,15 @@ PyAPI_FUNC(PyObject * const *) _PyArg_UnpackKeywords(
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void _PyArg_Fini(void);
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#endif /* Py_LIMITED_API */
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PyAPI_FUNC(int) PyModule_AddObject(PyObject *, const char *, PyObject *);
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// Add an attribute with name 'name' and value 'obj' to the module 'mod.
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// On success, return 0 on success.
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// On error, raise an exception and return -1.
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PyAPI_FUNC(int) PyModule_AddObjectRef(PyObject *mod, const char *name, PyObject *value);
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// Similar to PyModule_AddObjectRef() but steal a reference to 'obj'
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// (Py_DECREF(obj)) on success (if it returns 0).
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PyAPI_FUNC(int) PyModule_AddObject(PyObject *mod, const char *, PyObject *value);
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PyAPI_FUNC(int) PyModule_AddIntConstant(PyObject *, const char *, long);
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PyAPI_FUNC(int) PyModule_AddStringConstant(PyObject *, const char *, const char *);
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#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03090000
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@ -0,0 +1,3 @@
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Added :c:func:`PyModule_AddObjectRef` function: similar to
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:c:func:`PyModule_AddObjectRef` but don't steal a reference to the value on
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success. Patch by Victor Stinner.
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@ -634,56 +634,70 @@ va_build_stack(PyObject **small_stack, Py_ssize_t small_stack_len,
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int
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PyModule_AddObject(PyObject *m, const char *name, PyObject *o)
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PyModule_AddObjectRef(PyObject *mod, const char *name, PyObject *value)
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{
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PyObject *dict;
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if (!PyModule_Check(m)) {
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if (!PyModule_Check(mod)) {
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PyErr_SetString(PyExc_TypeError,
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"PyModule_AddObject() needs module as first arg");
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"PyModule_AddObjectRef() first argument "
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"must be a module");
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return -1;
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}
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if (!o) {
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if (!PyErr_Occurred())
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PyErr_SetString(PyExc_TypeError,
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"PyModule_AddObject() needs non-NULL value");
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if (!value) {
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if (!PyErr_Occurred()) {
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PyErr_SetString(PyExc_SystemError,
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"PyModule_AddObjectRef() must be called "
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"with an exception raised if value is NULL");
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}
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return -1;
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}
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dict = PyModule_GetDict(m);
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PyObject *dict = PyModule_GetDict(mod);
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if (dict == NULL) {
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/* Internal error -- modules must have a dict! */
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PyErr_Format(PyExc_SystemError, "module '%s' has no __dict__",
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PyModule_GetName(m));
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PyModule_GetName(mod));
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return -1;
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}
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if (PyDict_SetItemString(dict, name, o))
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if (PyDict_SetItemString(dict, name, value)) {
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return -1;
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Py_DECREF(o);
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}
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return 0;
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}
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int
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PyModule_AddObject(PyObject *mod, const char *name, PyObject *value)
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{
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int res = PyModule_AddObjectRef(mod, name, value);
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if (res == 0) {
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Py_DECREF(value);
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}
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return res;
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}
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int
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PyModule_AddIntConstant(PyObject *m, const char *name, long value)
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{
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PyObject *o = PyLong_FromLong(value);
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if (!o)
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PyObject *obj = PyLong_FromLong(value);
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if (!obj) {
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return -1;
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if (PyModule_AddObject(m, name, o) == 0)
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return 0;
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Py_DECREF(o);
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return -1;
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}
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int res = PyModule_AddObjectRef(m, name, obj);
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Py_DECREF(obj);
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return res;
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}
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int
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PyModule_AddStringConstant(PyObject *m, const char *name, const char *value)
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{
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PyObject *o = PyUnicode_FromString(value);
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if (!o)
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PyObject *obj = PyUnicode_FromString(value);
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if (!obj) {
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return -1;
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if (PyModule_AddObject(m, name, o) == 0)
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return 0;
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Py_DECREF(o);
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return -1;
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}
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int res = PyModule_AddObjectRef(m, name, obj);
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Py_DECREF(obj);
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return res;
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}
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int
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@ -696,11 +710,5 @@ PyModule_AddType(PyObject *module, PyTypeObject *type)
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const char *name = _PyType_Name(type);
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assert(name != NULL);
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Py_INCREF(type);
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if (PyModule_AddObject(module, name, (PyObject *)type) < 0) {
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Py_DECREF(type);
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return -1;
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}
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return 0;
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return PyModule_AddObjectRef(module, name, (PyObject *)type);
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}
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