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327 lines
12 KiB
C
327 lines
12 KiB
C
/* The PyObject_ memory family: high-level object memory interfaces.
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See pymem.h for the low-level PyMem_ family.
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*/
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#ifndef Py_OBJIMPL_H
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#define Py_OBJIMPL_H
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#include "pymem.h"
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* BEWARE:
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Each interface exports both functions and macros. Extension modules should
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use the functions, to ensure binary compatibility across Python versions.
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Because the Python implementation is free to change internal details, and
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the macros may (or may not) expose details for speed, if you do use the
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macros you must recompile your extensions with each Python release.
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Never mix calls to PyObject_ memory functions with calls to the platform
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malloc/realloc/ calloc/free, or with calls to PyMem_.
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*/
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/*
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Functions and macros for modules that implement new object types.
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- PyObject_New(type, typeobj) allocates memory for a new object of the given
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type, and initializes part of it. 'type' must be the C structure type used
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to represent the object, and 'typeobj' the address of the corresponding
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type object. Reference count and type pointer are filled in; the rest of
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the bytes of the object are *undefined*! The resulting expression type is
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'type *'. The size of the object is determined by the tp_basicsize field
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of the type object.
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- PyObject_NewVar(type, typeobj, n) is similar but allocates a variable-size
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object with room for n items. In addition to the refcount and type pointer
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fields, this also fills in the ob_size field.
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- PyObject_Del(op) releases the memory allocated for an object. It does not
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run a destructor -- it only frees the memory. PyObject_Free is identical.
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- PyObject_Init(op, typeobj) and PyObject_InitVar(op, typeobj, n) don't
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allocate memory. Instead of a 'type' parameter, they take a pointer to a
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new object (allocated by an arbitrary allocator), and initialize its object
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header fields.
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Note that objects created with PyObject_{New, NewVar} are allocated using the
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specialized Python allocator (implemented in obmalloc.c), if WITH_PYMALLOC is
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enabled. In addition, a special debugging allocator is used if PYMALLOC_DEBUG
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is also #defined.
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In case a specific form of memory management is needed (for example, if you
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must use the platform malloc heap(s), or shared memory, or C++ local storage or
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operator new), you must first allocate the object with your custom allocator,
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then pass its pointer to PyObject_{Init, InitVar} for filling in its Python-
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specific fields: reference count, type pointer, possibly others. You should
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be aware that Python no control over these objects because they don't
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cooperate with the Python memory manager. Such objects may not be eligible
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for automatic garbage collection and you have to make sure that they are
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released accordingly whenever their destructor gets called (cf. the specific
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form of memory management you're using).
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Unless you have specific memory management requirements, use
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PyObject_{New, NewVar, Del}.
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*/
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/*
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* Raw object memory interface
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* ===========================
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*/
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/* Functions to call the same malloc/realloc/free as used by Python's
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object allocator. If WITH_PYMALLOC is enabled, these may differ from
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the platform malloc/realloc/free. The Python object allocator is
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designed for fast, cache-conscious allocation of many "small" objects,
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and with low hidden memory overhead.
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PyObject_Malloc(0) returns a unique non-NULL pointer if possible.
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PyObject_Realloc(NULL, n) acts like PyObject_Malloc(n).
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PyObject_Realloc(p != NULL, 0) does not return NULL, or free the memory
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at p.
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Returned pointers must be checked for NULL explicitly; no action is
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performed on failure other than to return NULL (no warning it printed, no
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exception is set, etc).
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For allocating objects, use PyObject_{New, NewVar} instead whenever
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possible. The PyObject_{Malloc, Realloc, Free} family is exposed
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so that you can exploit Python's small-block allocator for non-object
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uses. If you must use these routines to allocate object memory, make sure
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the object gets initialized via PyObject_{Init, InitVar} after obtaining
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the raw memory.
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*/
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PyAPI_FUNC(void *) PyObject_Malloc(size_t);
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PyAPI_FUNC(void *) PyObject_Realloc(void *, size_t);
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PyAPI_FUNC(void) PyObject_Free(void *);
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/* Macros */
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#ifdef WITH_PYMALLOC
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#ifdef PYMALLOC_DEBUG
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PyAPI_FUNC(void *) _PyObject_DebugMalloc(size_t nbytes);
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PyAPI_FUNC(void *) _PyObject_DebugRealloc(void *p, size_t nbytes);
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PyAPI_FUNC(void) _PyObject_DebugFree(void *p);
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PyAPI_FUNC(void) _PyObject_DebugDumpAddress(const void *p);
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PyAPI_FUNC(void) _PyObject_DebugCheckAddress(const void *p);
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PyAPI_FUNC(void) _PyObject_DebugMallocStats(void);
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#define PyObject_MALLOC _PyObject_DebugMalloc
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#define PyObject_Malloc _PyObject_DebugMalloc
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#define PyObject_REALLOC _PyObject_DebugRealloc
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#define PyObject_Realloc _PyObject_DebugRealloc
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#define PyObject_FREE _PyObject_DebugFree
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#define PyObject_Free _PyObject_DebugFree
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#else /* WITH_PYMALLOC && ! PYMALLOC_DEBUG */
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#define PyObject_MALLOC PyObject_Malloc
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#define PyObject_REALLOC PyObject_Realloc
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#define PyObject_FREE PyObject_Free
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#endif
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#else /* ! WITH_PYMALLOC */
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#define PyObject_MALLOC PyMem_MALLOC
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#define PyObject_REALLOC PyMem_REALLOC
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/* This is an odd one! For backward compatability with old extensions, the
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PyMem "release memory" functions have to invoke the object allocator's
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free() function. When pymalloc isn't enabled, that leaves us using
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the platform free(). */
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#define PyObject_FREE free
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#endif /* WITH_PYMALLOC */
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#define PyObject_Del PyObject_Free
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#define PyObject_DEL PyObject_FREE
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/* for source compatibility with 2.2 */
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#define _PyObject_Del PyObject_Free
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/*
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* Generic object allocator interface
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* ==================================
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*/
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/* Functions */
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PyAPI_FUNC(PyObject *) PyObject_Init(PyObject *, PyTypeObject *);
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PyAPI_FUNC(PyVarObject *) PyObject_InitVar(PyVarObject *,
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PyTypeObject *, int);
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PyAPI_FUNC(PyObject *) _PyObject_New(PyTypeObject *);
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PyAPI_FUNC(PyVarObject *) _PyObject_NewVar(PyTypeObject *, int);
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#define PyObject_New(type, typeobj) \
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( (type *) _PyObject_New(typeobj) )
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#define PyObject_NewVar(type, typeobj, n) \
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( (type *) _PyObject_NewVar((typeobj), (n)) )
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/* Macros trading binary compatibility for speed. See also pymem.h.
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Note that these macros expect non-NULL object pointers.*/
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#define PyObject_INIT(op, typeobj) \
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( (op)->ob_type = (typeobj), _Py_NewReference((PyObject *)(op)), (op) )
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#define PyObject_INIT_VAR(op, typeobj, size) \
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( (op)->ob_size = (size), PyObject_INIT((op), (typeobj)) )
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#define _PyObject_SIZE(typeobj) ( (typeobj)->tp_basicsize )
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/* _PyObject_VAR_SIZE returns the number of bytes (as size_t) allocated for a
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vrbl-size object with nitems items, exclusive of gc overhead (if any). The
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value is rounded up to the closest multiple of sizeof(void *), in order to
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ensure that pointer fields at the end of the object are correctly aligned
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for the platform (this is of special importance for subclasses of, e.g.,
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str or long, so that pointers can be stored after the embedded data).
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Note that there's no memory wastage in doing this, as malloc has to
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return (at worst) pointer-aligned memory anyway.
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*/
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#if ((SIZEOF_VOID_P - 1) & SIZEOF_VOID_P) != 0
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# error "_PyObject_VAR_SIZE requires SIZEOF_VOID_P be a power of 2"
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#endif
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#define _PyObject_VAR_SIZE(typeobj, nitems) \
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(size_t) \
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( ( (typeobj)->tp_basicsize + \
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(nitems)*(typeobj)->tp_itemsize + \
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(SIZEOF_VOID_P - 1) \
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) & ~(SIZEOF_VOID_P - 1) \
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)
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#define PyObject_NEW(type, typeobj) \
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( (type *) PyObject_Init( \
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(PyObject *) PyObject_MALLOC( _PyObject_SIZE(typeobj) ), (typeobj)) )
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#define PyObject_NEW_VAR(type, typeobj, n) \
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( (type *) PyObject_InitVar( \
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(PyVarObject *) PyObject_MALLOC(_PyObject_VAR_SIZE((typeobj),(n)) ),\
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(typeobj), (n)) )
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/* This example code implements an object constructor with a custom
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allocator, where PyObject_New is inlined, and shows the important
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distinction between two steps (at least):
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1) the actual allocation of the object storage;
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2) the initialization of the Python specific fields
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in this storage with PyObject_{Init, InitVar}.
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PyObject *
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YourObject_New(...)
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{
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PyObject *op;
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op = (PyObject *) Your_Allocator(_PyObject_SIZE(YourTypeStruct));
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if (op == NULL)
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return PyErr_NoMemory();
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PyObject_Init(op, &YourTypeStruct);
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op->ob_field = value;
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...
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return op;
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}
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Note that in C++, the use of the new operator usually implies that
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the 1st step is performed automatically for you, so in a C++ class
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constructor you would start directly with PyObject_Init/InitVar
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*/
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/*
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* Garbage Collection Support
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* ==========================
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*/
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/* C equivalent of gc.collect(). */
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long PyGC_Collect(void);
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/* Test if a type has a GC head */
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#define PyType_IS_GC(t) PyType_HasFeature((t), Py_TPFLAGS_HAVE_GC)
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/* Test if an object has a GC head */
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#define PyObject_IS_GC(o) (PyType_IS_GC((o)->ob_type) && \
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((o)->ob_type->tp_is_gc == NULL || (o)->ob_type->tp_is_gc(o)))
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PyAPI_FUNC(PyVarObject *) _PyObject_GC_Resize(PyVarObject *, int);
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#define PyObject_GC_Resize(type, op, n) \
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( (type *) _PyObject_GC_Resize((PyVarObject *)(op), (n)) )
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/* for source compatibility with 2.2 */
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#define _PyObject_GC_Del PyObject_GC_Del
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/* GC information is stored BEFORE the object structure. */
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typedef union _gc_head {
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struct {
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union _gc_head *gc_next;
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union _gc_head *gc_prev;
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int gc_refs;
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} gc;
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long double dummy; /* force worst-case alignment */
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} PyGC_Head;
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extern PyGC_Head *_PyGC_generation0;
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#define _Py_AS_GC(o) ((PyGC_Head *)(o)-1)
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#define _PyGC_REFS_UNTRACKED (-2)
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#define _PyGC_REFS_REACHABLE (-3)
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#define _PyGC_REFS_TENTATIVELY_UNREACHABLE (-4)
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/* Tell the GC to track this object. NB: While the object is tracked the
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* collector it must be safe to call the ob_traverse method. */
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#define _PyObject_GC_TRACK(o) do { \
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PyGC_Head *g = _Py_AS_GC(o); \
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if (g->gc.gc_refs != _PyGC_REFS_UNTRACKED) \
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Py_FatalError("GC object already tracked"); \
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g->gc.gc_refs = _PyGC_REFS_REACHABLE; \
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g->gc.gc_next = _PyGC_generation0; \
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g->gc.gc_prev = _PyGC_generation0->gc.gc_prev; \
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g->gc.gc_prev->gc.gc_next = g; \
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_PyGC_generation0->gc.gc_prev = g; \
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} while (0);
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/* Tell the GC to stop tracking this object.
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* gc_next doesn't need to be set to NULL, but doing so is a good
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* way to provoke memory errors if calling code is confused.
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*/
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#define _PyObject_GC_UNTRACK(o) do { \
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PyGC_Head *g = _Py_AS_GC(o); \
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assert(g->gc.gc_refs != _PyGC_REFS_UNTRACKED); \
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g->gc.gc_refs = _PyGC_REFS_UNTRACKED; \
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g->gc.gc_prev->gc.gc_next = g->gc.gc_next; \
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g->gc.gc_next->gc.gc_prev = g->gc.gc_prev; \
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g->gc.gc_next = NULL; \
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} while (0);
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PyAPI_FUNC(PyObject *) _PyObject_GC_Malloc(size_t);
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PyAPI_FUNC(PyObject *) _PyObject_GC_New(PyTypeObject *);
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PyAPI_FUNC(PyVarObject *) _PyObject_GC_NewVar(PyTypeObject *, int);
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PyAPI_FUNC(void) PyObject_GC_Track(void *);
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PyAPI_FUNC(void) PyObject_GC_UnTrack(void *);
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PyAPI_FUNC(void) PyObject_GC_Del(void *);
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#define PyObject_GC_New(type, typeobj) \
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( (type *) _PyObject_GC_New(typeobj) )
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#define PyObject_GC_NewVar(type, typeobj, n) \
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( (type *) _PyObject_GC_NewVar((typeobj), (n)) )
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/* This is here for the sake of backwards compatibility. Extensions that
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* use the old GC API will still compile but the objects will not be
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* tracked by the GC. */
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#define PyGC_HEAD_SIZE 0
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#define PyObject_GC_Init(op)
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#define PyObject_GC_Fini(op)
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#define PyObject_AS_GC(op) (op)
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#define PyObject_FROM_GC(op) (op)
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/* Test if a type supports weak references */
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#define PyType_SUPPORTS_WEAKREFS(t) \
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(PyType_HasFeature((t), Py_TPFLAGS_HAVE_WEAKREFS) \
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&& ((t)->tp_weaklistoffset > 0))
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#define PyObject_GET_WEAKREFS_LISTPTR(o) \
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((PyObject **) (((char *) (o)) + (o)->ob_type->tp_weaklistoffset))
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#ifdef __cplusplus
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}
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#endif
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#endif /* !Py_OBJIMPL_H */
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