为通过ctypes返回给python的对象分配内存 [英] deallocating memory for objects returned to python through ctypes
问题描述
我正在使用ctypes将MyDll中的c函数扩展为python。
I am using ctypes for extending my c functions in MyDll to python.
from ctypes import cdll
libX = cdll.LoadLibrary("d:\\MyTestProject\\debug\\MyDll.dll")
在.py文件中我还有一个类
further in the .py file i have a class the methods of which call the functions in MyDll through ctypes.
Class MyTestClass:
def __init__(self,id):
libA.MyTestClassInDLL_new.restype = ctypes.c_void_p
self.obj = libA.MyTestClassInDLL_new(id)
对应的c函数MyTestClassInDLL_new已在MyDll中定义为-
the corresponding c function MyTestClassInDLL_new has been defined in MyDll as -
extern "C" __declspec(dllexport) void * MyTestClassInDLL_new(char* id)
{
pTestObject = new CMyTestClassInDLL(CString(id));
return (void *)pTestObject;
}
注意,我正在使用new实例化我的vc ++ dll中的该对象并返回指向它的指针。我已在.py文件中将此函数的重新类型设置为ctypes.c_void_p。
Note I am using new to instantiate this object in my vc++ dll and returning the pointer to it. I have set the restype of this function in the .py file as ctypes.c_void_p.
我执行的脚本包含以下内容-
The script that I execute contains the following -
testob = MyTestClass("5")
这很好用。我在这里获得的testob进一步用于调用其从MyDll内部调用c函数的方法。
this works fine. the testob that i obtain here is used further to call its methods which internally call the c functions from MyDll.
但是,对象是使用MyDll中的new创建的,并通过MyTestClassInDLL_new返回()功能。该物体如何被销毁?在某个地方,我需要使用delete pTestObject,以便调用其析构函数进行清理并释放内存。
However the object was created using new in MyDll and returned through MyTestClassInDLL_new() function. How is this object to be destroyed ? somewhere i need to use delete pTestObject so that its destructor is called which does the cleanup and the memory is deallocated.
推荐答案
我通常通过添加一个extern destroy对象函数来处理此问题,该函数可以将指针传递回并删除它。
I typically handle this by adding an extern destroy object function that I can pass the pointer back to and delete it.
CPP:
SomeClass* createObj()
{
return new SomeClass();
}
void destroyObj(SomeClass* pObj){
delete pObj;
pObj = NULL;
}
H:
extern "C" {
SomeClass* createObj();
void destroyObj(SomeClass*);
}
PY:
class SomeObj:
def __init__(self):
self.soLib = cdll.LoadLibrary(PATH_SO)
_createObj = self.soLib.createObj
_createObj.restype = POINTER(c_long)
self._objRef = _createObj()
## do stuff with self._objRef
def __del__(self):
self.soLib.destroyObj(self._objRef)
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