C++ pointer to an array

Question

I know that in C++, the name of an array is just the pointer to the first element of the array. For example:

int foo[5];

=> foo is a pointer of type int, and it points to the first element in the array, which is a[0]

But then, we have this:

int (*foo)[5]

Here, foo is a pointer to an array of type. So is foo a pointer to a pointer (of type int)?

Arrays are pointers with a bit more overhead like array size and padding. — SwiftMango
– SwiftMango, Commented Oct 17, 2012 at 4:39

Kerrek SB · Accepted Answer · 2012-10-17 03:37:14Z

5

This is an array of five ints:

int a[5];

This is a pointer to an array of five ints:

int (*p)[5] = &a;

This is a pointer to an int:

int * q = a;  // same as &a[0]

answered Oct 17, 2012 at 3:37

Kerrek SB

480k96 gold badges904 silver badges1.1k bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Sergey Kalinichenko · Accepted Answer · 2012-10-17 03:44:17Z

2

in C++, the name of an array is just the pointer to the first element of the array

That's not correct: a name of an array can be converted to a corresponding pointer type "for free", but it is definitely not a pointer. The easiest way you can tell is by comparing sizes of a pointer and of an array:

int foo[5];
int *ptr;
cout << sizeof(foo) << endl;
cout << sizeof(ptr) << endl;

Your second example is a pointer to an array of ints of size 5.

cout << sizeof(foo) << endl;
cout << sizeof(*foo) << endl;

In a 32-bit environment this prints 4 and 20, as expected.

edited Oct 17, 2012 at 3:44

answered Oct 17, 2012 at 3:37

Sergey Kalinichenko

729k85 gold badges1.2k silver badges1.6k bronze badges

4 Comments

Chin Over a year ago

So in the second case, if it's a pointer to an array, what is the type of the pointer? Is it just "array"?

Sergey Kalinichenko Over a year ago

@Chin Its type is "a pointer to an array of integers of size five" (pretty long name, huh?).

Sergey Kalinichenko Over a year ago

@Chin Take a look at this link to ideone that illustrates the point from my last comment.

Chin Over a year ago

Thanks. In my second example, I just want to know from a memory-diagram perspective whether it is a pointer to a pointer. But since it's not a pointer in the first example... I think I get the idea

Collectives™ on Stack Overflow

C++ pointer to an array

2 Answers 2

Comments

4 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Related