You can't use pointer arithmetic on void pointers, so how do arrays of void pointers work?

Question

From reading tutorials, my understanding is that behind the scenes the operator([]) does the same thing as pointer arithmetic.

Learncpp has the following to say "It turns out that when the compiler sees the subscript operator ([]), it actually translates that into a pointer addition and dereference!".

Wikibooks then says this "A variable declared as an array of some type acts as a pointer to that type. When used by itself, it points to the first element of the array."

Then after reading about void pointers, I was curious to know how would an array of them work? I imagine that my understanding of something must be wrong.

For an example the following two should be identical.

a)

void* array[5];
array[1] = nullptr;

b)

void* array[5];
*(array + 1) = nullptr;

Remember that arrays decays to pointers to their first element. That is, array decays to &array[0]. And that decayed pointer has the type void** which you can do pointer arithmetic on. — Some programmer dude
– Some programmer dude, Commented Jul 7, 2019 at 9:21
what is your question? the size of a void pointer is known (architecture specific though....). e.g. 32bit. Thus (array +1) will actually add 4bytes (size of each element if sizeof(void) is 4) to the base address. — nivpeled
– nivpeled, Commented Jul 7, 2019 at 9:22
My question was, how does the operator([]) work with since there seemed to be a contradiction, but the above comment cleared that up. In fact I'd like him to post that as the answer, so I can mark it as correct. — Lillu
– Lillu, Commented Jul 7, 2019 at 9:25

Stephan Dollberg · Accepted Answer · 2019-07-07 09:23:40Z

2

An array of pointers is basically just ** - void** in your case.

You know the size of void* as it's just another pointer.

answered Jul 7, 2019 at 9:23

Stephan Dollberg

34.9k16 gold badges83 silver badges110 bronze badges

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

Collectives™ on Stack Overflow

You can't use pointer arithmetic on void pointers, so how do arrays of void pointers work?

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related