Error: control may reach end of non-void function in C

You are getting this error because if your for loop breaks due to breaking condition i < n; then it don’t find any return statement after for loop (see the below, I mentioned in code as comment).

for (int i = 0; i < n; i++){
    if (values[i] == value){
        return true;
        break;
    }
    else{ 
        return false;
    }
}
  // here you should add either return true or false     
}

If for loop break due to i >= n then control comes to the position where I commented and there is no return statement present. Hence you are getting an error “reach end of non-void function in C”.

Additionally, remove break after return statement. if return executes then break never get chance to execute and break loop.

   return true;  -- it returns from here. 
    break;  -- " remove it it can't executes after return "

Check your compiler should give you a warning – ‘unreachable code’.