c - No More Confusing Pointers

Question

Following is my code:

#include <stdio.h>
int main()
{
     char a[10]="Hi!";  
    void f(char b[])
    {
        // 1. printf("*a is:%s
",*a);
        printf("&a is:%p
",&a);
        // 2. printf("&&a is:%p
",&(&a));
        printf("a's address is:%p
",a);
        printf("a's value is:%s
",a);
        printf("b's address is:%p
",b);
        printf("b's value is:%s
",b);
        // 3. printf("*b is:%s
",*b);
        printf("&b is:%s
",&b);
    }

    f(a);

    return 1;
    getch();
}

Running the above code gives the output:

&a is:0028FF1C
a's address is:0028FF1C
a's value is:Hi!
b's address is:0028FF1C
b's value is:Hi!
&b is:∟?(

In the Output: Why are there different outputs for &a and &b; Although a and b have same reference.

Further,

I've mentioned 3 comments by their number. If I remove slashes one by one and execute them,I get following 2 issues:

1. On executing comment no. 1 & 3:

   "abc.exe has stopped working."
   

2. On executing comment no. 2:

   abc.c: In function 'f':
   abc.c:14:32: error: lvalue required as unary '&' operand
             printf("&&a is:%p
   ",&(&a));
                           ^
   

Answer 1

• Point 1: Nested functions are not standard C. They are supported as GCC extension..

• Point 2: printf("&b is:%s ",&b); is wrong and invokes UB, because of improper format specifier. You need to change that to

   printf("&b is:%p
  ",(void *)&b);
  

• Point 3: &(&a) is wrong. the operand for & needs to be an lvalue, not another address, which is not an lvalue.

  Related: C11, chapter §6.5.3.2, for the operand type

  The operand of the unary & operator shall be either a function designator, the result of a [] or unary * operator, or an lvalue that designates an object that is not a bit-field and is not declared with the register storage-class specifier.

  and the return type

  ....result is not an lvalue.