keymap and Xsync

[viollet.benoit at free.fr]

The following code:

  locale(LC_ALL,"");
  ...
  keysym = XKeycodeToKeysym (dpy, keycode,0);
  std::cout << (int) keycode << " " << (int) keysym << std::endl;
  XSync (dpy, False);
  keysym = XKeycodeToKeysym (dpy, keycode,0);
  std::cout << (int) keycode << " " << (int) keysym << std::endl;

gives
24 97
24 113

So, Xsync changes the keymap from "fr" to "us". But when I add at the beginning: system("setxkbmap fr"), it works.
24 97
24 97

What can I do ?

P.S. Sorry for my english.