array initializer inside class

Question

While working on an arduino project, I created some C++ code that does not compile. After understanding where it stops the essence of it is as follows:

const int xx[]={12,5};

void setup() {
  // put your setup code here, to run once:
const int yy[]={12,5};
}

class aaaa{
  //compilation stops here giving error too many intialiazers for 'const int[0]'
  const int zz[]={12,5};
};


void loop() {
  // put your main code here, to run repeatedly:
}

The question is why it does not compile giving error "too many intialiazers for 'const int[0]'. Should it behave like that ?

The fact that you are redefining new arrays with the same name and values as a const global array indicates to me that you may be confused about what const int xx[]={12,5}; means. What are you trying to achieve exactly? — François Andrieux
– François Andrieux, Commented Aug 27, 2020 at 15:33
No it was just an abstract example taken out of my code when I understood where the problem was. Thus I should use static in order to overcome the compiler limitations, or just put the number of elements. What I haven't realized is that the compiler puts the constants inside the structure, something that I don't know if it is needed by the standard or not in that case. — George Kourtis
– George Kourtis, Commented Aug 27, 2020 at 17:00

Alan Birtles · Accepted Answer · 2020-08-27 15:38:50Z

1

Your first array declares a global variable, this is allowed to have a size defined by an initialiser.

Your second array is a local variable, again this is allowed to have a size defined by an initialiser.

Your third array is a member of a structure, structure members must have a fixed size so that the structure itself has a fixed size. The size isn't allowed to be deduced from the initialiser.

Clang gives a clearer error message:

error: array bound cannot be deduced from an in-class initializer

answered Aug 27, 2020 at 15:38

Alan Birtles

38.3k4 gold badges39 silver badges73 bronze badges

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

2 Comments

George Kourtis Over a year ago

To me it seems that the const inside a class does not take space inside the data of the structure related to the class as it is essentially a field shared among all the instances of the class. So the inability to deduce is just a compiler problem to be corrected, unless I miss something I would like to know.

Alan Birtles Over a year ago

no, it is not static so it is a member of the class, the const is irrelevant

Collectives™ on Stack Overflow

array initializer inside class

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related