C API 设计:谁应该分配? [英] C API design: Who should allocate?

问题描述

在 C API 中分配内存的正确/首选方法是什么?

What is the proper/preferred way to allocate memory in a C API?

起初，我可以看到两个选项:

I can see, at first, two options:

1) 让调用者完成所有(外部)内存处理:

1) Let the caller do all the (outer) memory handling:

myStruct *s = malloc(sizeof(s));
myStruct_init(s);

myStruct_foo(s);

myStruct_destroy(s);
free(s);

_init 和 _destroy 函数是必要的，因为内部可能会分配更多的内存，并且必须在某处处理.

The _init and _destroy functions are necessary since some more memory may be allocated inside, and it must be handled somewhere.

这样做的缺点是比较长，但在某些情况下也可以消除 malloc(例如，它可以传递一个堆栈分配的结构:

This has the disadvantage of being longer, but also the malloc can be eliminated in some cases (e.g., it can be passed a stack-allocated struct:

int bar() {
    myStruct s;
    myStruct_init(&s);

    myStruct_foo(&s);

    myStruct_destroy(&s);
}

另外，调用者必须知道结构体的大小.

Also, it's necessary for the caller to know the size of the struct.

2) 隐藏 _init 中的 malloc 和 _destroy 中的 free.

2) Hide mallocs in _init and frees in _destroy.

优点:代码更短，因为无论如何都会调用函数.完全不透明的结构.

Advantages: shorter code, since the functions are going to be called anyway. Completely opaque structures.

缺点:不能传递以不同方式分配的结构体.

Disadvantages: Can't be passed a struct allocated in a different way.

myStruct *s = myStruct_init();

myStruct_foo(s);

myStruct_destroy(foo);

我目前倾向于第一种情况；再说一次，我不知道 C API 设计.

I'm currently leaning for the first case; then again, I don't know about C API design.

推荐答案

我最喜欢的精心设计的 C API 示例是 GTK+ 使用您描述的方法 #2.

My favourite example of a well-design C API is GTK+ which uses method #2 that you describe.

虽然您的方法#1 的另一个优点不仅是您可以在堆栈上分配对象，而且您可以多次重用同一个实例.如果这不是一个常见的用例，那么#2 的简单性可能是一个优势.

Although another advantage of your method #1 is not just that you could allocate the object on the stack, but also that you could reuse the same instance multiple times. If that's not going to be a common use case, then the simplicity of #2 is probably an advantage.

当然，这只是我的意见:)

Of course, that's just my opinion :)

这篇关于C API 设计:谁应该分配?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！