What is the difference between structure and function scope in C?

Question

Consider this piece of code

   int main(void)
   {
       typedef struct {
           int i;
       } s;

       struct {
           s s;
       } t;

       return 0;
   }

It compiles fine. Now take a look at this one

   int main(void)
   {
       typedef struct {
           int i;
       } s;

       s s;
       return 0;
   }

This code will not compile -

‘s’ redeclared as different kind of symbol.

Question: Why is it correct to have "ss;" as a declaration inside a structure, but not correct to have this definition inside a function?

Answer 1

In upper example member s is a local to struct. You cannot use it without using ts syntax, so there is no conflict with structure type s .

In lower example structure type s , and variable s are in the same scope, so it is unclear which you are referring to.

Answer 2

作为struct成员，标识符s是明确的，因为您将始终将其作为somestruct.s或someptr->s 。