Ncurses, unicode: problems on some terminals

Question

I'm trying to make ncurses work with unicodes. I found a nice tutorial here. However I'm having troubles with the following code:

#include <locale.h>
#include <curses.h>
#include <stdlib.h>

int
main (int argc, char *argv[])
{
  setlocale(LC_ALL, "");

  initscr();

  printw("Euro\n");

  printw("€\n");              // literal Unicode
  printw("\u20ac\n");         // escaped Unicode (C99)

  printw("%lc\n", L'€');      // wint_t
  printw("%ls\n", L"€");      // wchar_t
  addwstr(L"\u20AC\n");       // wchar_t

  printw("\xe2\x82\xac\n");   // utf-8 encoded
  addstr("\xe2\x82\xac\n");   // utf-8 encoded

  for (int i = 0; i < 10; i++)
  {
    printw("%c %lc\n", '0' + i, L'０' + i);
  }

  getch();
  endwin();

  return EXIT_SUCCESS;
}

I can summarize the problems in two points

1. When I compile with gcc -c -Wall -Wextra -g -o build/main.o src/main.c I get the message

   src/main.c:19:3: warning: implicit declaration of function ‘addwstr’; did you mean ‘addstr’? [-Wimplicit-function-declaration]
   

   I do not know why I'm getting such a message. In fact, in the curses.h I can see the line

   #define addwstr(wstr)                   waddwstr(stdscr,(wstr)) 
   [...]    
   extern NCURSES_EXPORT(int) waddwstr (WINDOW *,const wchar_t *);         /* generated:WIDEC */
   

   I use Arch as a distro and ncurses package is installed regularly.

2. After linking with gcc -lncursesw -D_GNU_SOURCE -D_DEFAULT_SOURCE -o bin/main build/main.o if a run the program on some consoles (i.e. KDE Konsole) the output is ugly

   Euro
    ~B
    ~B
   
    ~B
    ~B
   0 1 2 3 4 5 6 7 8 9 
   

   while on some other (i.e. the one embedded in vscode), the output is the desired one:

   Euro
   €
   €
   €
   €
   €
   €
   €
   0 ０
   1 １
   2 ２
   3 ３
   4 ４
   5 ５
   6 ６
   7 ７
   8 ８
   9 ９
   

What is going on? Can you tell me how to make my code compile without warning and work on every console?

EDIT

I think I found a solution to issue 2). It is enough to use

setlocale(LC_ALL, "en_US.UTF-8");

to make things work properly