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
       7  extern "C" {
       8  #endif
       9  
      10  #ifndef Py_BUILD_CORE
      11  #  error "this header requires Py_BUILD_CORE define"
      12  #endif
      13  
      14  typedef 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      26     XXX no longer valid?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  */
      38  PyAPI_FUNC(PyArena*) _PyArena_New(void);
      39  PyAPI_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   */
      53  PyAPI_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   */
      59  PyAPI_FUNC(int) _PyArena_AddPyObject(PyArena *, PyObject *);
      60  
      61  #ifdef __cplusplus
      62  }
      63  #endif
      64  #endif /* !Py_INTERNAL_PYARENA_H */