Using random() in a header file

Question

#ifndef FOO_H
#define FOO_H
struct Foo{
 int randInt = random(0, 101);
};
#endif

I have a header file with a struct like above but when I compile I get this error:

'random' was not declared in this scope

How can I use random() in a header file?

Answer 1

Add #include <Arduino.h> like this

#ifndef FOO_H
#define FOO_H
#include <Arduino.h>
struct Foo{
 int randInt = random(0, 101);
};
#endif

Answer 2

The struct is a declaration of a type. You cannot mix it with the initialization. This is how it could be:

In foo.h:

#ifndef FOO_H
#define FOO_H
struct Foo{
 int randInt;
};
extern struct Foo foo;
struct Foo *initFoo(struct Foo *foo_ptr);
#endif

In foo.c:

#include "foo.h"
struct Foo foo;
struct Foo *initFoo(struct Foo *foo_ptr) {
 if (!foo_ptr)
 return NULL;
 foo_ptr->randInt = random(0, 101);
 return foo_ptr;
}

random() is a function and therefore its return value cannot be used as static initializer. Unless -std=c++11 or -std=gnu++11 are enabled.

• Chris: It's valid C++ code I don't see why it would be different for an Arduino. The code works fine after I #include <Arduino.h>.
• Igor Stoppa: What is the outcome? Did you try to compile exactly the code you put in your question?
• Chris: I answered my question and it works as is. The only problem was that random() was defined in my header file so I had to include the Arduino library. Someone commented for me to do but it's gone now, I guess they deleted it.
• Igor Stoppa: With gcc, it works only with -std=c++11 or -std=gnu++11. Probably the Arduino ide turns them on by default.
• BrettFolkins: Arduino does in fact have -std=gnu++11 by default