8000 bpo-39542: Make PyObject_INIT() opaque in limited C API (GH-18363) · python/cpython@f58bd7c · GitHub
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bpo-39542: Make PyObject_INIT() opaque in limited C API (GH-18363)
In the limited C API, PyObject_INIT() and PyObject_INIT_VAR() are now defined as aliases to PyObject_Init() and PyObject_InitVar() to make their implementation opaque. It avoids to leak implementation details in the limited C API. Exclude the following functions from the limited C API, move them from object.h to cpython/object.h: * _Py_NewReference() * _Py_ForgetReference() * _PyTraceMalloc_NewReference() * _Py_GetRefTotal()
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6 files changed

+77
-49
lines changed

6 files changed

+77
-49
lines changed

‎Include/cpython/object.h

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@@ -6,6 +6,22 @@
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extern "C" {
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#endif
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PyAPI_FUNC(void) _Py_NewReference(PyObject *op);
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#ifdef Py_TRACE_REFS
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/* Py_TRACE_REFS is such major surgery that we call external routines. */
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PyAPI_FUNC(void) _Py_ForgetReference(PyObject *);
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#endif
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/* Update the Python traceback of an object. This function must be called
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when a memory block is reused from a free list. */
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PyAPI_FUNC(int) _PyTraceMalloc_NewReference(PyObject *op);
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#ifdef Py_REF_DEBUG
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PyAPI_FUNC(Py_ssize_t) _Py_GetRefTotal(void);
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#endif
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/********************* String Literals ****************************************/
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/* This structure helps managing static strings. The basic usage goes like this:
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Instead of doing

‎Include/cpython/objimpl.h

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@@ -6,6 +6,39 @@
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extern "C" {
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#endif
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/* Inline functions trading binary compatibility for speed:
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PyObject_INIT() is the fast version of PyObject_Init(), and
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PyObject_INIT_VAR() is the fast version of PyObject_InitVar().
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These inline functions must not be called with op=NULL. */
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static inline PyObject*
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_PyObject_INIT(PyObject *op, PyTypeObject *typeobj)
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{
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assert(op != NULL);
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Py_TYPE(op) = typeobj;
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if (PyType_GetFlags(typeobj) & Py_TPFLAGS_HEAPTYPE) {
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Py_INCREF(typeobj);
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}
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_Py_NewReference(op);
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return op;
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}
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#define PyObject_INIT(op, typeobj) \
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_PyObject_INIT(_PyObject_CAST(op), (typeobj))
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static inline PyVarObject*
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_PyObject_INIT_VAR(PyVarObject *op, PyTypeObject *typeobj, Py_ssize_t size)
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{
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assert(op != NULL);
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Py_SIZE(op) = size;
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PyObject_INIT((PyObject *)op, typeobj);
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return op;
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}
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#define PyObject_INIT_VAR(op, typeobj, size) \
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_PyObject_INIT_VAR(_PyVarObject_CAST(op), (typeobj), (size))
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/* This function returns the number of allocated memory blocks, regardless of size */
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PyAPI_FUNC(Py_ssize_t) _Py_GetAllocatedBlocks(void);
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‎Include/object.h

Lines changed: 1 addition & 14 deletions
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@@ -233,8 +233,7 @@ PyAPI_FUNC(int) PyObject_SetAttr(PyObject *, PyObject *, PyObject *);
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PyAPI_FUNC(int) PyObject_HasAttr(PyObject *, PyObject *);
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PyAPI_FUNC(PyObject *) PyObject_SelfIter(PyObject *);
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PyAPI_FUNC(PyObject *) PyObject_GenericGetAttr(PyObject *, PyObject *);
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PyAPI_FUNC(int) PyObject_GenericSetAttr(PyObject *,
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PyObject *, PyObject *);
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PyAPI_FUNC(int) PyObject_GenericSetAttr(PyObject *, PyObject *, PyObject *);
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#if !defined(Py_LIMITED_API) || Py_LIMITED_API+0 >= 0x03030000
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PyAPI_FUNC(int) PyObject_GenericSetDict(PyObject *, PyObject *, void *);
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#endif
@@ -381,20 +380,8 @@ you can count such references to the type object.)
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PyAPI_DATA(Py_ssize_t) _Py_RefTotal;
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PyAPI_FUNC(void) _Py_NegativeRefcount(const char *filename, int lineno,
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PyObject *op);
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PyAPI_FUNC(Py_ssize_t) _Py_GetRefTotal(void);
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#endif /* Py_REF_DEBUG */
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/* Update the Python traceback of an object. This function must be called
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when a memory block is reused from a free list. */
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PyAPI_FUNC(int) _PyTraceMalloc_NewReference(PyObject *op);
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PyAPI_FUNC(void) _Py_NewReference(PyObject *op);
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#ifdef Py_TRACE_REFS
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/* Py_TRACE_REFS is such major surgery that we call external routines. */
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PyAPI_FUNC(void) _Py_ForgetReference(PyObject *);
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#endif
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PyAPI_FUNC(void) _Py_Dealloc(PyObject *);
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static inline void _Py_INCREF(PyObject *op)

‎Include/objimpl.h

Lines changed: 12 additions & 31 deletions
Original file line numberDiff line numberDiff line change
@@ -127,40 +127,21 @@ PyAPI_FUNC(PyVarObject *) _PyObject_NewVar(PyTypeObject *, Py_ssize_t);
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#define PyObject_NewVar(type, typeobj, n) \
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( (type *) _PyObject_NewVar((typeobj), (n)) )
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/* Inline functions trading binary compatibility for speed:
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PyObject_INIT() is the fast version of PyObject_Init(), and
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PyObject_INIT_VAR() is the fast version of PyObject_InitVar.
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See also pymem.h.
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These inline functions expect non-NULL object pointers. */
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static inline PyObject*
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_PyObject_INIT(PyObject *op, PyTypeObject *typeobj)
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{
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assert(op != NULL);
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Py_TYPE(op) = typeobj;
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if (PyType_GetFlags(typeobj) & Py_TPFLAGS_HEAPTYPE) {
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Py_INCREF(typeobj);
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}
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_Py_NewReference(op);
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return op;
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}
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#define PyObject_INIT(op, typeobj) \
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_PyObject_INIT(_PyObject_CAST(op), (typeobj))
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#define _PyObject_SIZE(typeobj) ( (typeobj)->tp_basicsize )
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static inline PyVarObject*
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_PyObject_INIT_VAR(PyVarObject *op, PyTypeObject *typeobj, Py_ssize_t size)
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{
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assert(op != NULL);
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Py_SIZE(op) = size;
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PyObject_INIT((PyObject *)op, typeobj);
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return op;
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}
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#define PyObject_INIT_VAR(op, typeobj, size) \
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_PyObject_INIT_VAR(_PyVarObject_CAST(op), (typeobj), (size))
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#ifdef Py_LIMITED_API
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/* Define PyObject_INIT() and PyObject_INIT_VAR() as aliases to PyObject_Init()
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and PyObject_InitVar() in the limited C API for compatibility with the
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CPython C API. */
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# define PyObject_INIT(op, typeobj) \
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PyObject_Init(_PyObject_CAST(op), (typeobj))
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# define PyObject_INIT_VAR(op, typeobj, size) \
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PyObject_InitVar(_PyVarObject_CAST(op), (typeobj), (size))
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#else
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/* PyObject_INIT() and PyObject_INIT_VAR() are defined in cpython/objimpl.h */
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#endif
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#define _PyObject_SIZE(typeobj) ( (typeobj)->tp_basicsize )
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/* _PyObject_VAR_SIZE returns the number of bytes (as size_t) allocated for a
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vrbl-size object with nitems items, exclusive of gc overhead (if any). The

‎Misc/NEWS.d/next/C API/2020-02-05-12-40-51.bpo-39542.si-_Zq.rst

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@@ -0,0 +1,7 @@
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In the limited C API, ``PyObject_INIT()`` and ``PyObject_INIT_VAR()`` are
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now defined as aliases to :c:func:`PyObject_Init` and
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:c:func:`PyObject_InitVar` to make their implementation opaque. It avoids to
4+
leak implementation details in the limited C API. Exclude the following
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functions from the limited C API: ``_Py_NewReference()``,
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``_Py_ForgetReference()``, ``_PyTraceMalloc_NewReference()`` and
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``_Py_GetRefTotal()``.

‎Objects/object.c

Lines changed: 8 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -139,9 +139,11 @@ Py_DecRef(PyObject *o)
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PyObject *
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PyObject_Init(PyObject *op, PyTypeObject *tp)
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{
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if (op == NULL)
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/* Any changes should be reflected in PyObject_INIT() macro */
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if (op == NULL) {
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return PyErr_NoMemory();
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/* Any changes should be reflected in PyObject_INIT (objimpl.h) */
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}
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Py_TYPE(op) = tp;
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if (PyType_GetFlags(tp) & Py_TPFLAGS_HEAPTYPE) {
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Py_INCREF(tp);
@@ -153,9 +155,11 @@ PyObject_Init(PyObject *op, PyTypeObject *tp)
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PyVarObject *
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PyObject_InitVar(PyVarObject *op, PyTypeObject *tp, Py_ssize_t size)
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{
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if (op == NULL)
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/* Any changes should be reflected in PyObject_INIT_VAR() macro */
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if (op == NULL) {
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return (PyVarObject *) PyErr_NoMemory();
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/* Any changes should be reflected in PyObject_INIT_VAR */
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}
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Py_SIZE(op) = size;
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PyObject_Init((PyObject *)op, tp);
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return op;

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