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bpo-40170: PyObject_NEW() becomes an alias to PyObject_New() (GH-19379)

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The PyObject_NEW() macro becomes an alias to the PyObject_New()
macro, and the PyObject_NEW_VAR() macro becomes an alias to the
PyObject_NewVar() macro, to hide implementation details. They no
longer access directly the PyTypeObject.tp_basicsize member.

Exclude _PyObject_SIZE() and _PyObject_VAR_SIZE() macros from
the limited C API.

Replace PyObject_NEW() with PyObject_New() and replace
PyObject_NEW_VAR() with PyObject_NewVar().
This commit is contained in:
Victor Stinner 2020-04-08 00:38:15 +02:00 • committed by GitHub
parent f9dd51e7db
commit 9205520d8c
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11 changed files with 81 additions and 78 deletions
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70
Include/objimpl.h
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@ -122,12 +122,18 @@ PyAPI_FUNC(PyVarObject *) PyObject_InitVar(PyVarObject *,
PyAPI_FUNC(PyObject *) _PyObject_New(PyTypeObject *);
PyAPI_FUNC(PyVarObject *) _PyObject_NewVar(PyTypeObject *, Py_ssize_t);
#define PyObject_New(type, typeobj) \
( (type *) _PyObject_New(typeobj) )
#define PyObject_New(type, typeobj) ((type *)_PyObject_New(typeobj))
// Alias to PyObject_New(). In Python 3.8, PyObject_NEW() called directly
// PyObject_MALLOC() with _PyObject_SIZE().
#define PyObject_NEW(type, typeobj) PyObject_New(type, typeobj)
#define PyObject_NewVar(type, typeobj, n) \
( (type *) _PyObject_NewVar((typeobj), (n)) )
#define _PyObject_SIZE(typeobj) ( (typeobj)->tp_basicsize )
// Alias to PyObject_New(). In Python 3.8, PyObject_NEW() called directly
// PyObject_MALLOC() with _PyObject_VAR_SIZE().
#define PyObject_NEW_VAR(type, typeobj, n) PyObject_NewVar(type, typeobj, n)
#ifdef Py_LIMITED_API
@ -143,64 +149,6 @@ PyAPI_FUNC(PyVarObject *) _PyObject_NewVar(PyTypeObject *, Py_ssize_t);
#endif
/* _PyObject_VAR_SIZE returns the number of bytes (as size_t) allocated for a
vrbl-size object with nitems items, exclusive of gc overhead (if any). The
value is rounded up to the closest multiple of sizeof(void *), in order to
ensure that pointer fields at the end of the object are correctly aligned
for the platform (this is of special importance for subclasses of, e.g.,
str or int, so that pointers can be stored after the embedded data).
Note that there's no memory wastage in doing this, as malloc has to
return (at worst) pointer-aligned memory anyway.
*/
#if ((SIZEOF_VOID_P - 1) & SIZEOF_VOID_P) != 0
# error "_PyObject_VAR_SIZE requires SIZEOF_VOID_P be a power of 2"
#endif
#define _PyObject_VAR_SIZE(typeobj, nitems) \
_Py_SIZE_ROUND_UP((typeobj)->tp_basicsize + \
(nitems)*(typeobj)->tp_itemsize, \
SIZEOF_VOID_P)
#define PyObject_NEW(type, typeobj) \
( (type *) PyObject_Init( \
(PyObject *) PyObject_MALLOC( _PyObject_SIZE(typeobj) ), (typeobj)) )
#define PyObject_NEW_VAR(type, typeobj, n) \
( (type *) PyObject_InitVar( \
(PyVarObject *) PyObject_MALLOC(_PyObject_VAR_SIZE((typeobj),(n)) ),\
(typeobj), (n)) )
/* This example code implements an object constructor with a custom
allocator, where PyObject_New is inlined, and shows the important
distinction between two steps (at least):
1) the actual allocation of the object storage;
2) the initialization of the Python specific fields
in this storage with PyObject_{Init, InitVar}.
PyObject *
YourObject_New(...)
{
PyObject *op;
op = (PyObject *) Your_Allocator(_PyObject_SIZE(YourTypeStruct));
if (op == NULL)
return PyErr_NoMemory();
PyObject_Init(op, &YourTypeStruct);
op->ob_field = value;
...
return op;
}
Note that in C++, the use of the new operator usually implies that
the 1st step is performed automatically for you, so in a C++ class
constructor you would start directly with PyObject_Init/InitVar
*/
/*
* Garbage Collection Support
* ==========================