cpython/Include/pyarena.h at pythoncapi · pythoncapi/cpython · GitHub

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/* An arena-like memory interface for the compiler.

#ifndef Py_LIMITED_API

#ifndef Py_PYARENA_H

#define Py_PYARENA_H

#ifdef __cplusplus

extern "C" {

#endif

typedef struct _arena PyArena;

/* PyArena_New() and PyArena_Free() create a new arena and free it,

respectively. Once an arena has been created, it can be used

to allocate memory via PyArena_Malloc(). Pointers to PyObject can

also be registered with the arena via PyArena_AddPyObject(), and the

arena will ensure that the PyObjects stay alive at least until

PyArena_Free() is called. When an arena is freed, all the memory it

allocated is freed, the arena releases internal references to registered

PyObject*, and none of its pointers are valid.

XXX (tim) What does "none of its pointers are valid" mean? Does it

XXX mean that pointers previously obtained via PyArena_Malloc() are

XXX no longer valid? (That's clearly true, but not sure that's what

XXX the text is trying to say.)

PyArena_New() returns an arena pointer. On error, it

returns a negative number and sets an exception.

XXX (tim): Not true. On error, PyArena_New() actually returns NULL,

XXX and looks like it may or may not set an exception (e.g., if the

XXX internal PyList_New(0) returns NULL, PyArena_New() passes that on

XXX and an exception is set; OTOH, if the internal

XXX block_new(DEFAULT_BLOCK_SIZE) returns NULL, that's passed on but

XXX an exception is not set in that case).

PyAPI_FUNC(PyArena *) PyArena_New(void);

PyAPI_FUNC(void) PyArena_Free(PyArena *);

/* Mostly like malloc(), return the address of a block of memory spanning

* `size` bytes, or return NULL (without setting an exception) if enough

* new memory can't be obtained. Unlike malloc(0), PyArena_Malloc() with

* size=0 does not guarantee to return a unique pointer (the pointer

* returned may equal one or more other pointers obtained from

* PyArena_Malloc()).

* Note that pointers obtained via PyArena_Malloc() must never be passed to

* the system free() or realloc(), or to any of Python's similar memory-

* management functions. PyArena_Malloc()-obtained pointers remain valid

* until PyArena_Free(ar) is called, at which point all pointers obtained

* from the arena `ar` become invalid simultaneously.

PyAPI_FUNC(void *) PyArena_Malloc(PyArena *, size_t size);

/* This routine isn't a proper arena allocation routine. It takes

* a PyObject* and records it so that it can be DECREFed when the

* arena is freed.

PyAPI_FUNC(int) PyArena_AddPyObject(PyArena *, PyObject *);

#ifdef __cplusplus

}

#endif

#endif /* !Py_PYARENA_H */

#endif /* Py_LIMITED_API */

cpython/Include/pyarena.h at pythoncapi · pythoncapi/cpython · GitHub

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