返回结构数组或结构指针数组？

If you need to return a struct from a function, you would normally return a pointer to the struct instead.

如果需要从函数返回结构，通常会返回指向结构的指针。

If you then want to return an array of structs, is it recommended to:

如果您想返回结构数组，建议：

1. return an array of structures (pointer to the first element)
2. 返回一个结构数组（指向第一个元素的指针）
3. or return an array of struct pointers?
4. 或者返回一个struct指针数组？

I have drawn a diagram for the two options below:

我已经为下面的两个选项绘制了一个图表：

1:

1：

2:

2：

Given the following struct definition

给出以下结构定义

struct values {
    int a;
    int b;
};

here is some sample code for accessing the fields of the structs from the two options:

这里有一些示例代码，用于从两个选项访问结构的字段：

Option #1:

选项1：

 struct values *vals = get_values1();
 printf("%d, %d\n", values[0].a, values[1].b);

Option #2:

选项＃2：

 struct values **vals = get_values2();
 printf("%d, %d\n", values[0]->a, values[1]->b);

4 个解决方案

#1

The only issue I see to not use version 1, is that it might be easier to identify the number of structures (returned) in the second version, as a NULL pointer can be used as a stopper element, whereas in the first version it might not be possible to define a stopper element.

我看到不使用版本1的唯一问题是，在第二个版本中识别结构（返回）的数量可能更容易，因为NULL指针可以用作止动元素，而在第一个版本中它可能不可能定义止动元件。

#2

Unless you have a good reason to return a pointer to pointers (for example, if you want to modify the pointers themselves later on), I think a pointer to the struct is good enough. No need to trick around with double pointers.

除非你有充分的理由返回指针指针（例如，如果你想稍后修改指针），我认为指向结构的指针就足够了。无需用双指针欺骗。

#3

As an example for a beginners book on C, the question would clearly be satisfied better by option 1 (no indirection) as was pointed out by the answers so far. If there is more to the question however (e.g. which is the best way to pass around structs in a large framework) then I would certainly go for option 2. Why? structs are complex units of data and tend to become standalone entities which are allocated and passed around and disposed in differing ways - all code that handles them by direct access will need a rewrite if data handling becomes more complex.

作为关于C的初学者书的一个例子，到目前为止答案中指出的选项1（没有间接）显然更好地满足了这个问题。如果问题还有更多（例如哪个是在大型框架中传递结构的最佳方法）那么我肯定会选择选项2.为什么？结构是复杂的数据单元，往往成为独立的实体，它们被分配和传递并以不同的方式处理 - 如果数据处理变得更加复杂，那么通过直接访问处理它们的所有代码都需要重写。

#4

For me, as the number of indirections grow, the code complexity grows even faster. Thus I prefer your Option #1: struct values *foo().

对我来说，随着间接数量的增加，代码复杂性变得更快。因此，我更喜欢你的选项＃1：struct values * foo（）。

Should data requirements push toward #2: struct values **foo(), suggest creating a new type typedef struct values *ValuesSet and returning a pointer to that: ValuesSet *foo().

如果数据要求推向＃2：struct values ** foo（），建议创建一个新类型typedef struct values * ValuesSet并返回指向它的指针：ValuesSet * foo（）。