python3.12/internal/pycore_pyarena.h

0001 /* An arena-like memory interface for the compiler.
0002  */
0003
0004 #ifndef Py_INTERNAL_PYARENA_H
0005 #define Py_INTERNAL_PYARENA_H
0006 #ifdef __cplusplus
0007 extern "C" {
0008 #endif
0009
0010 #ifndef Py_BUILD_CORE
0011 #  error "this header requires Py_BUILD_CORE define"
0012 #endif
0013
0014 typedef struct _arena PyArena;
0015
0016 /* _PyArena_New() and _PyArena_Free() create a new arena and free it,
0017    respectively.  Once an arena has been created, it can be used
0018    to allocate memory via _PyArena_Malloc().  Pointers to PyObject can
0019    also be registered with the arena via _PyArena_AddPyObject(), and the
0020    arena will ensure that the PyObjects stay alive at least until
0021    _PyArena_Free() is called.  When an arena is freed, all the memory it
0022    allocated is freed, the arena releases internal references to registered
0023    PyObject*, and none of its pointers are valid.
0024    XXX (tim) What does "none of its pointers are valid" mean?  Does it
0025    XXX mean that pointers previously obtained via _PyArena_Malloc() are
0026    XXX no longer valid?  (That's clearly true, but not sure that's what
0027    XXX the text is trying to say.)
0028
0029    _PyArena_New() returns an arena pointer.  On error, it
0030    returns a negative number and sets an exception.
0031    XXX (tim):  Not true.  On error, _PyArena_New() actually returns NULL,
0032    XXX and looks like it may or may not set an exception (e.g., if the
0033    XXX internal PyList_New(0) returns NULL, _PyArena_New() passes that on
0034    XXX and an exception is set; OTOH, if the internal
0035    XXX block_new(DEFAULT_BLOCK_SIZE) returns NULL, that's passed on but
0036    XXX an exception is not set in that case).
0037 */
0038 PyAPI_FUNC(PyArena*) _PyArena_New(void);
0039 PyAPI_FUNC(void) _PyArena_Free(PyArena *);
0040
0041 /* Mostly like malloc(), return the address of a block of memory spanning
0042  * `size` bytes, or return NULL (without setting an exception) if enough
0043  * new memory can't be obtained.  Unlike malloc(0), _PyArena_Malloc() with
0044  * size=0 does not guarantee to return a unique pointer (the pointer
0045  * returned may equal one or more other pointers obtained from
0046  * _PyArena_Malloc()).
0047  * Note that pointers obtained via _PyArena_Malloc() must never be passed to
0048  * the system free() or realloc(), or to any of Python's similar memory-
0049  * management functions.  _PyArena_Malloc()-obtained pointers remain valid
0050  * until _PyArena_Free(ar) is called, at which point all pointers obtained
0051  * from the arena `ar` become invalid simultaneously.
0052  */
0053 PyAPI_FUNC(void*) _PyArena_Malloc(PyArena *, size_t size);
0054
0055 /* This routine isn't a proper arena allocation routine.  It takes
0056  * a PyObject* and records it so that it can be DECREFed when the
0057  * arena is freed.
0058  */
0059 PyAPI_FUNC(int) _PyArena_AddPyObject(PyArena *, PyObject *);
0060
0061 #ifdef __cplusplus
0062 }
0063 #endif
0064 #endif /* !Py_INTERNAL_PYARENA_H */