understanding C namespaces

Question

Quoting from here,

In C, there are two different namespaces of types: a namespace of struct/union/enum tag names and a namespace of typedef names.

Answer 1

Your 2nd example does not show "no conflict". There is a conflict! Try this:

#include 
int four(void) { return 4; }
struct dummy { int member; };
int main(void) {
    struct dummy four;
    four.member = four();
}

And now this

#include 
int four(void) { return 4; }
struct dummy { int member; };
int main(void) {
    int (*fx)(void) = four; /* "save" function */
    struct dummy four;     /* hide it         */
    four.member = fx();    /* use "hidden" fx */
}

In your 2nd example, the variable four hides the function four().