1/* An arena-like memory interface for the compiler.
2 */
3
4#ifndef Py_INTERNAL_PYARENA_H
5#define Py_INTERNAL_PYARENA_H
6#ifdef __cplusplus
7extern "C" {
8#endif
9
10#ifndef Py_BUILD_CORE
11#  error "this header requires Py_BUILD_CORE define"
12#endif
13
14typedef struct _arena PyArena;
15
16/* _PyArena_New() and _PyArena_Free() create a new arena and free it,
17   respectively.  Once an arena has been created, it can be used
18   to allocate memory via _PyArena_Malloc().  Pointers to PyObject can
19   also be registered with the arena via _PyArena_AddPyObject(), and the
20   arena will ensure that the PyObjects stay alive at least until
21   _PyArena_Free() is called.  When an arena is freed, all the memory it
22   allocated is freed, the arena releases internal references to registered
23   PyObject*, and none of its pointers are valid.
24   XXX (tim) What does "none of its pointers are valid" mean?  Does it
25   XXX mean that pointers previously obtained via _PyArena_Malloc() are
26   XXX no longer valid?  (That's clearly true, but not sure that's what
27   XXX the text is trying to say.)
28
29   _PyArena_New() returns an arena pointer.  On error, it
30   returns a negative number and sets an exception.
31   XXX (tim):  Not true.  On error, _PyArena_New() actually returns NULL,
32   XXX and looks like it may or may not set an exception (e.g., if the
33   XXX internal PyList_New(0) returns NULL, _PyArena_New() passes that on
34   XXX and an exception is set; OTOH, if the internal
35   XXX block_new(DEFAULT_BLOCK_SIZE) returns NULL, that's passed on but
36   XXX an exception is not set in that case).
37*/
38PyAPI_FUNC(PyArena*) _PyArena_New(void);
39PyAPI_FUNC(void) _PyArena_Free(PyArena *);
40
41/* Mostly like malloc(), return the address of a block of memory spanning
42 * `size` bytes, or return NULL (without setting an exception) if enough
43 * new memory can't be obtained.  Unlike malloc(0), _PyArena_Malloc() with
44 * size=0 does not guarantee to return a unique pointer (the pointer
45 * returned may equal one or more other pointers obtained from
46 * _PyArena_Malloc()).
47 * Note that pointers obtained via _PyArena_Malloc() must never be passed to
48 * the system free() or realloc(), or to any of Python's similar memory-
49 * management functions.  _PyArena_Malloc()-obtained pointers remain valid
50 * until _PyArena_Free(ar) is called, at which point all pointers obtained
51 * from the arena `ar` become invalid simultaneously.
52 */
53PyAPI_FUNC(void*) _PyArena_Malloc(PyArena *, size_t size);
54
55/* This routine isn't a proper arena allocation routine.  It takes
56 * a PyObject* and records it so that it can be DECREFed when the
57 * arena is freed.
58 */
59PyAPI_FUNC(int) _PyArena_AddPyObject(PyArena *, PyObject *);
60
61#ifdef __cplusplus
62}
63#endif
64#endif /* !Py_INTERNAL_PYARENA_H */
65