SWIG - 使用 %newobject 进行垃圾收集

发布于 2024-10-09 19:47:32 字数 688 浏览 5 评论 0原文

在我的 C 代码中，我有以下结构：

typedef struct my_structure{
    char* str1;
    char* str2;
}MyStruct;

和一个返回 MyStruct 指针的函数：

MyStruct* foo();

在 foo 内部，我为 MyStruct 、 str1 和 str2 分配了内存，如下所示：

MyStruct* obj = malloc(sizeof(MyStruct));

obj.str1 = malloc(256);
obj.str2 = malloc(256);

我想从 python、java、C# 和 PHP 调用 foo我不想在这个过程中出现任何内存泄漏。

我不确定写入：

%newobject foo;
MyStruct* foo();

是否保证垃圾收集器将为结构及其内部的字符串释放内存。

我不想让调用者有义务为 str1 和 str2 显式释放内存，因为我正在寻找一种自动释放内存的方法。这可能吗？

在这种情况下我必须使用“newfree”类型映射吗？

如果您能为我提供一个示例来展示实现此目的的最佳方法，我将不胜感激。

谢谢！

原文

In my C code, I have the following structure :

typedef struct my_structure{
    char* str1;
    char* str2;
}MyStruct;

And a function that returns a MyStruct pointer :

MyStruct* foo();

Inside foo, I have allocated memory for MyStruct , str1 and str2, as follows:

MyStruct* obj = malloc(sizeof(MyStruct));

obj.str1 = malloc(256);
obj.str2 = malloc(256);

I want to call foo from python, java, C# and PHP and I don't want to have any memory leak in this process.

I am not sure if writing:

%newobject foo;
MyStruct* foo();

guarantees that the garbage collector will free memory for both the structure and the strings inside it.

I didn't want to obligate the caller to explicit free memory for str1 and str2 as I was looking for an automatic way of freeing memory. Is this possible?

Do I have to use "newfree" typemap in this case?

I would greatly appreciate if you could provide me an example showing the best way to accomplish this.

Thanks!

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偏闹i 2024-10-16 19:47:32

typemap(newfree) 立即释放返回的 %newobject 使用的内存，例如当 char* 返回值转换为 Python 字符串并且分配的对象不再是时需要。我认为您想要的是 %extend SWIG 围绕您的 C 结构生成的类包装器以提供析构函数：

%newobject foo;

%extend MyStruct {
    ~MyStruct() {
       free($self->str1);
       free($self->str2);
    }
}

如果这解决了您的问题，请发表评论。这是基于我自己的实验，我可以在 SWIG 文档中找到并在我生成的简单包装器中正常工作。

typemap(newfree) frees the memory used by the returned %newobject immediately, such as when a char* return value is converted into a Python string and the allocated object is no longer needed. I think what you want is %extend the class wrapper that SWIG generates around your C structure to provide a destructor:

%newobject foo;

%extend MyStruct {
    ~MyStruct() {
       free($self->str1);
       free($self->str2);
    }
}

Please comment if this solves your issue. This is based on my own experimentation with what I could find in the SWIG documentation and worked correctly in the simple wrapper I generated.

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