C++, why is array=ptr legal?

Question

Recently i saw this piece of code. Shouldnt this line be a compile error?char arr[4]="Abc";

What happens here? Is arr a pointer? is the char* copied into an array on stack? is this legal in all version of C++ (and what about C?). I tested and seen this works in VS and code pad which i believe uses gcc

-edit- Just for fun I tried replacing "Abc" with a static const char *. It gave me an invalid initializer error.

int main()
{
    int j=97;
    char arr[4]="Abc";
    printf(arr,j);
    getch();
    return 0;
}

Answer 1

It is equivalent to

char arr[4] = {'A', 'b', 'c', 0};

which is in turn equivalent to:

char arr[4];
arr[0] = 'A';
arr[1] = 'b';
arr[2] = 'c';
arr[3] = 0;

Answer 2

Character arrays can be initialized with string literals, it just assigns each element character by character. It's just a language feature.

---

And no, arr is not a pointer. It's an array. "Abc" is a string literal, which is also a character array.

Answer 3

array = ptr is not a legal assignment (if array has an array type and ptr has the corresponding pointer type). In the code you have shown, though, the = introduces an initializer as it is part of a declaration. It is not an assignment.

It is legal to initialize an array of char with a string constant.

Answer 4

String literal is not a pointer. String literal is an character array. So, what you have in your example is an array = array initialization, not an array = pointer as you seem to believe.

Yet in general it is indeed illegal to initialize one array with another array, in both C and C++.

However, in both C and C++ there's one exception from that rule: character arrays can be initialized with string literals. (Note: initialization is allowed; assignment won't work). Each element of the array gets initailized with the corresponding character from the literal (which also implicitly include a terminating zero character at the end). In C++ it is required that the recipient array's size has enough space for the terminating zero. In C the terminating zero is allowed to "fall off", if the recipient array is one character short.

Also, you are not required to specify the array size explicitly. You can do

char arr[] = "Abc";

and the compiler will automatically figure out that you need a 4 element array.