F: struct declaration

[Konstantin8105]

struct s* p = NULL; // tag naming an unknown struct declares it
struct s { int a; }; // definition for the struct pointed to by p
void g(void)
{
    struct s; // forward declaration of a new, local struct s
              // this hides global struct s until the end of this block
    struct s *p;  // pointer to local struct s
                  // without the forward declaration above,
                  // this would point at the file-scope s
    struct s { char* p; }; // definitions of the local struct s
}

see http://en.cppreference.com/w/c/language/struct

[Konstantin8105]

struct y;
struct x { struct y *p; /* ... */ };
struct y { struct x *q; /* ... */ };

int vv(){
struct y;
struct x2 { struct y *p2; /* ... */ };
struct y { struct x2 *q; /* ... */ };
}

[Konstantin8105]

// Link: http://en.cppreference.com/w/c/language/struct
struct yS;
struct x  { struct yS *p;  int ax;};
struct yS { struct x  *q;  int ay;};

int test_vv(){
       struct yS var_y;
       struct x  var_x;
       var_x.p = &var_y;
       var_x.ax = 10;
       var_y.q = &var_x;
       var_y.ay = 42;
       is_eq(var_x.ax , 10);
       is_eq((*var_x.p).ay , 42);
       
       struct yS;
       struct x2  { struct yS *p2; float bx2; };
       struct yS  { struct x2  *q; float by ; };

       struct yS var_y2;
       struct x2 var_x2;
       var_x2.p2 = &var_y2;
       var_x2.bx2 = 100;
       var_y2.q = &var_x2;
       var_y2.by = 420;
       is_eq(var_x2.bx2 , 100);
       is_eq((*var_x2.p2).by , 420);
}