why the size of the C++ class with enumerations declared is 1?

Question

class test
{
public:
    enum t_number
    {
        ZERO,
        ONE
    };

    enum t_test
    {
        TWO,
        THREE
    };
};

Why the size of the above class is 1 and not 8?

And when I do this in main()

cout << "value of enum"<< test::ONE

I get output as 1.

Does that mean memory is allocated for the enum?

Because you declared only types in your class (no members) and the minimum size of a class is 1. — drescherjm, Jan 17 '18 at 14:46
Because you don't have any member variables. An object still needs to take some place, to be addressable, so it still is one single byte so it could be stored in memory. — Some programmer dude, Jan 17 '18 at 14:46
Why would it be 8? It contains no data. C++ doesn't allow 0 size objects (because that would lead to various bad things like multiple objects having the same address and arrays behaving super weird), so 1 is the ideal choice. — nwp, Jan 17 '18 at 14:46
Possible duplicate of [Why is the size of an empty class in C++ not zero?](https://stackoverflow.com/questions/2362097/why-is-the-size-of-an-empty-class-in-c-not-zero) — Raymond Chen, Jan 17 '18 at 15:34

score 0 · Accepted Answer · edited Jan 17 '18 at 15:26

0

Only data have size, you're not setting data in your class, you're defining types of data.

For the second part, recently added, you're asking to display test::ONE, like in C, enums are an abstraction of unsigned integers, so when you type :

enum foo {
    bar,
    baz,
    qux
};

It's exactly the same as typing

enum foo {
    bar = 0,
    baz = 1,
    qux = 2
};

So when you type this in your main

cout << "value of enum"<< test::ONE;

You just implicitely converting your test::ONE in its integer value.

Note that this implicit conversion would not exist with enum class in c++11.

edited Jan 17 '18 at 15:26

Pete Becker

answered Jan 17 '18 at 14:48

Steranoid

2

To be fair, types have a size as well. You can query the size of a type and get a meaningful answer. – François Andrieux Jan 17 '18 at 14:49
You mean to say "only data occupies storage". And even that can have exceptions. – StoryTeller - Unslander Monica Jan 17 '18 at 14:49

1 Answers1