使用Python的CFFI进行内存管理和析构函数的约定/free()? [英] Conventions for memory management and destructors / free() with Python's CFFI?

问题描述

如果我要包装C类:

from ._ffi import ffi, lib

class MyClass(object):
     def __init__(self):
         self._c_class = lib.MyClass_create()

确保调用lib.MyClass_destroy(…)的最佳做法是什么?

What are best practices for making sure that lib.MyClass_destroy(…) is called?

cffi是否在对象周围有某种包装器，当对Python对象进行GC处理时，这些包装器将调用析构函数，例如:

Does cffi have some sort of wrapper around objects that will call a destructor when the Python object is GC'd, for example something like:

my_obj = managed(lib.MyClass_create(), destructor=lib.MyClass_destroy)

还是应该在类的__del__中使用析构函数逻辑?像这样:

Or should that destructor logic be in the class's __del__? Something like:

class MyClass(object):
    def __del__(self):
        if self._c_class is not None:
            lib.MyClass_destroy(self._c_class)

这里的最佳做法是什么?

What are the best practices here?

推荐答案

看起来ffi.gc()是可行的方式.这是我写的小型包装程序，它也执行后malloc NULL检查:

It looks like ffi.gc() is the way to go. This is the small wrapper I've written which also does the post-malloc NULL check:

def managed(create, args, free):
    o = create(*args)
    if o == ffi.NULL:
        raise MemoryError("%s could not allocate memory" %(create.__name__, ))
    return ffi.gc(o, free)

例如:

c_class = managed(lib.MyClass_create, ("some_arg", 42),
                  lib.MyClass_destroy)

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