一个> typdef允许为数据类型创建更有意义的同义词，从而帮助定义程序的含义和文档化。此外，它们还有助于参数化程序以解决可移植性问题(K&R, pg147, C prog lang)。

B > 结构定义了一种类型。Structs允许方便地将变量集合分组，以便将(K&R, pg127, C prog lang.)作为单个单元处理

C > 结构的类型定义在上面的a中有解释。

对我来说，struct是自定义类型、容器、集合、命名空间或复杂类型，而typdef只是一种创建更多昵称的方法。

您(可选地)给结构的名称称为标记名称，正如前面所指出的，它本身并不是一个类型。要获得该类型，需要使用结构体前缀。

除了GTK+，我不确定tagname是否像struct类型的typedef一样常用，所以在c++中，这是可以识别的，你可以省略struct关键字，并使用tagname作为类型名:

struct MyStruct
{
  int i;
};

// The following is legal in C++:
MyStruct obj;
obj.i = 7;

让我们从最基本的开始，慢慢来。

下面是一个结构定义的例子:

struct point
  {
    int x, y;
  };

这里的名称点是可选的。

结构可以在定义期间声明，也可以在定义之后声明。

在定义期间声明

struct point
  {
    int x, y;
  } first_point, second_point;

在定义之后声明

struct point
  {
    int x, y;
  };
struct point first_point, second_point;

现在，仔细注意上面的最后一种情况;如果您决定稍后在代码中创建该类型，则需要编写struct point来声明该类型的结构。

输入类型。如果您打算在稍后使用相同的蓝图在程序中创建新的Structure (Structure是自定义数据类型)，那么在定义过程中使用typedef可能是一个好主意，因为您可以节省一些输入。

typedef struct point
  {
    int x, y;
  } Points;

Points first_point, second_point;

在命名自定义类型时要注意一点

没有什么可以阻止您在自定义类型名称的末尾使用_t后缀，但POSIX标准保留使用后缀_t来表示标准库类型名称。

一个> typdef允许为数据类型创建更有意义的同义词，从而帮助定义程序的含义和文档化。此外，它们还有助于参数化程序以解决可移植性问题(K&R, pg147, C prog lang)。

B > 结构定义了一种类型。Structs允许方便地将变量集合分组，以便将(K&R, pg127, C prog lang.)作为单个单元处理

C > 结构的类型定义在上面的a中有解释。

对我来说，struct是自定义类型、容器、集合、命名空间或复杂类型，而typdef只是一种创建更多昵称的方法。

我认为typedef甚至不可能实现前向声明。使用struct, enum和union允许在依赖关系(知道)是双向的情况下转发声明。

风格: 在c++中使用typedef是很有意义的。在处理需要多个和/或变量参数的模板时，它几乎是必要的。typedef有助于保持命名的直直性。

在C编程语言中并非如此。typedef的使用通常没有任何目的，只会混淆数据结构的使用。由于只有{struct (6)， enum (4)， union(5)}个按键被用于声明一个数据类型，因此结构的别名几乎没有任何用处。数据类型是联合还是结构?使用简单的非类型定义声明可以让您立即知道它是什么类型。

请注意Linux是如何在编写时严格避免typedef带来的这种无意义的别名的。结果是一个极简主义和干净的风格。

Linux内核编码风格第5章给出了使用typedef的优点和缺点(主要是缺点)。

Please don't use things like "vps_t". It's a mistake to use typedef for structures and pointers. When you see a vps_t a; in the source, what does it mean? In contrast, if it says struct virtual_container *a; you can actually tell what "a" is. Lots of people think that typedefs "help readability". Not so. They are useful only for: (a) totally opaque objects (where the typedef is actively used to hide what the object is). Example: "pte_t" etc. opaque objects that you can only access using the proper accessor functions. NOTE! Opaqueness and "accessor functions" are not good in themselves. The reason we have them for things like pte_t etc. is that there really is absolutely zero portably accessible information there. (b) Clear integer types, where the abstraction helps avoid confusion whether it is "int" or "long". u8/u16/u32 are perfectly fine typedefs, although they fit into category (d) better than here. NOTE! Again - there needs to be a reason for this. If something is "unsigned long", then there's no reason to do typedef unsigned long myflags_t; but if there is a clear reason for why it under certain circumstances might be an "unsigned int" and under other configurations might be "unsigned long", then by all means go ahead and use a typedef. (c) when you use sparse to literally create a new type for type-checking. (d) New types which are identical to standard C99 types, in certain exceptional circumstances. Although it would only take a short amount of time for the eyes and brain to become accustomed to the standard types like 'uint32_t', some people object to their use anyway. Therefore, the Linux-specific 'u8/u16/u32/u64' types and their signed equivalents which are identical to standard types are permitted -- although they are not mandatory in new code of your own. When editing existing code which already uses one or the other set of types, you should conform to the existing choices in that code. (e) Types safe for use in userspace. In certain structures which are visible to userspace, we cannot require C99 types and cannot use the 'u32' form above. Thus, we use __u32 and similar types in all structures which are shared with userspace. Maybe there are other cases too, but the rule should basically be to NEVER EVER use a typedef unless you can clearly match one of those rules. In general, a pointer, or a struct that has elements that can reasonably be directly accessed should never be a typedef.