add_wch() prints garbage

[Igor Liferenko]

Hi all

I compile the following program with

  gcc ncurses-test.c -o ncurses-test -lncursesw -D_XOPEN_SOURCE=600

Compilation succeeds without producing any warnings. But when I run
the binary, it prints garbage, not the character `ф'.
Interesting fact: the output changes if we change gnome-terminal's
window size.

My setup is: Debian 9 "stretch", UTF-8 environment, gnome-terminal.

Regards,
Igor

#include <ncursesw/curses.h>
#include <wchar.h>
#include <locale.h>

int main(void)
{
  setlocale(LC_CTYPE, "C.UTF-8");
  initscr();

  wchar_t c = L'ф';
  add_wch((cchar_t *)&c);
  refresh();

  getch();
  endwin();
  return 0;
}