Why use different a different tag and typedef for a struct?

Question

In C code, I\'ve seen the following:

typedef struct SomeStructTag {
    // struct members
} SomeStruct;

I\'m not clear on why this is any d

Answer 1

There is one functional reason for using a different tag between the typedef and the struct. This is when you're doing a linked list structure, where one of the fields in your struct is a pointer to an instance of the struct being defined. Since the statement isn't complete yet, you can't use the typedef name within the statement.

For example:

typedef struct {
    link_t* next;
    void*   data;
} link_t;

won't work, because you're trying to use link_t before the compiler has seen the symbol. Instead, you write it so:

typedef struct LL {
    struct LL* next;
    void*      data;
} link_t;

and struct LL is known to the compiler one line before you use it.