Default value of a struct member

Question

(I'm sure this question has already been answered, I'm just not sure on the right words to use to ask it. If someone would tell me what the correct terminology is that would be awesome!)

I'm implementing a HashSet in C++ for a data structures class, and I have a question about C++ syntax regarding structs. Here is my code:

struct HashNode
{
    T value;
    HashNode* next = nullptr;
};

Will this code correctly initialize the next pointer to nullptr when new HashNode is called? If not, what is the value of next after new HashNode?

What about http://stackoverflow.com/questions/16782103/initializing-default-values-in-a-struct? See second answer. — pingul, May 22 '16 at 02:31
Does it compile? NB These are *initial* values, not 'default' values. — user207421, May 22 '16 at 02:35
So you're asking whether the compiler produces correct object code for this construction? — user207421, May 22 '16 at 02:37
I suppose I am. I'm not really sure what "object code" means. — bakester14, May 22 '16 at 02:38
You're essentially asking whether the compile does what the code tells it to do. Well it does. Why would you feel the need to confirm that? — user207421, May 22 '16 at 02:43

songyuanyao · Accepted Answer · 2016-05-22T02:50:11.223

Will this code correctly initialize the next pointer to nullptr when new HashNode is called?

Yes, it will be initialized to nullptr. This is in-class brace-or-equal initializer (default member initializer) (since C++11), it will be used if the member is omitted in member initializer list.

Through a default member initializer, which is simply a brace or equals initializer included in the member declaration, which is used if the member is omitted in the member initializer list

If a member has a default member initializer and also appears in the member initialization list in a constructor, the default member initializer is ignored.

Thanks for the terminology! – bakester14 May 22 '16 at 02:40 — bakester14, May 22 '16 at 02:40

Default value of a struct member

1 Answers1