Question

Is something like this possible in C++ (on Arduino)?

#include "stdio.h"

String str = "foo";

int i[strLength()]; // <- define length of array in function

int strLength() {
  return str.length();
}

int main(void) {
   ...
}

Thank you in advance!

Answer 1

No. You would need i to be a pointer and allocate the array in your main:

int *i = NULL;

// etc.

int main(void) {

    i = (int*) malloc(sizeof(*i)*strLength());

    // etc.
}