Why can I not print non-ASCII characters to the console in curses mode? - unicode

Question

Please consider this simple snippet:
#include <stdio.h>
#include <curses.h>
#include <stdlib.h>
#include <stdbool.h>
#include <signal.h>
void cleanup(int signal)
{
endwin();
exit(0);
}
int main()
{
initscr();
struct sigaction cleanup_action = { .sa_handler = cleanup, .sa_flags = 0 };
sigfillset(&cleanup_action.sa_mask);
sigaction(SIGINT, &cleanup_action, NULL);
cbreak();
keypad(stdscr, TRUE);
noecho();
mvaddstr(2, 2, "🧱");
mvaddstr(2, 3, "🧱");
mvaddstr(2, 4, "🧱");
mvaddstr(3, 2, "⬜");
mvaddstr(3, 2, "⚾");
mvaddstr(3, 4, "⬜");
refresh();
while(true) getch();
return 0;
}
(No, I'm not certain that my clean-up on exit is correct, but that's not the point.)
Why are the emojis not being printed out?
When I run this program this is what I see:
���~_��
�~��~\
I don't understand this because according to POSIX specification:
addnstr, addstr, mvaddnstr, mvaddstr, mvwaddnstr, mvwaddstr waddnstr, waddstr - add a string of multi-byte characters without rendition to a window and advance cursor
"MULTI-BYTE" they say! So I guess this should print out correctly! I'm not limited to ASCII!
Also, I guess my terminal can handle these characters. This is because as opposed to curses.h, stdio.h is able to print them correctly:
#include <stdio.h>
int main()
{
printf("🧱⬜⚾\n");
return 0;
}
This prints out:
🧱⬜⚾
How can I print emojis with curses.h?