Include/pyarena.h

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  23      XXX no longer valid?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