allowed in C, but not in C++?

Followings are from Internet source (openasthra.com). Some are interesting and I didn't notice before:

1. sizeof (’1′) == sizeof (int) in C; but it is sizeof (char) in C++. So we get the result 4 and 1 with compiler gcc and g++, respectively.
2. Usually you should not use *alloc()/free() in C++, but they are the only such functions in C.
3. Functions need not be prototyped in C, but it is a must in C++.
4. struct a {  
            struct b {
                   int a; 
             };
   };
   struct b b; /*allowed in C, but not in C++ */
   not quite sure this one, but it has error in g++ compiler(error: aggregate 'b b' has incomplete type and cannot be defined. With following codes:
   sturct a {
           int a;
   }
   struct a a;
   some compilers are OK, some will report error.
5. const int b = 1; /* allowed in C and C++ */
   const int a ;      /* allowed in C, not in C++ */
6. global variables can be defined more than once in C, not in C++
   int a; /* works in C, C++ */
   int a = 10 ; /* works in C, not in C++ */
   int main()
   {...}
7. const a; /* equivalent to const in a; in C, illegal in C++ */
8. char s[7] = "1234567"; /* allowed in C, error in C++ */
9. K&R style function definitions are not allowed in C++, such as:
   void foo(a)
   int a;
   {...}