PVS-Studio warning V621 for Putty

#define snewn(n, type) ((type *)snmalloc((n), sizeof(type)))

void bareradioline(struct ctlpos *cp, int nacross, ...)
{
  va_list ap;
  struct radio *buttons;
  int i, nbuttons;

  va_start(ap, nacross);
  nbuttons = 0;
  while (1) {
    char *btext = va_arg(ap, char *);
    int bid;
    if (!btext)
      break;
    bid = va_arg(ap, int);
  }
  va_end(ap);
  buttons = snewn(nbuttons, struct radio);
  va_start(ap, nacross);
  for (i = 0; i < nbuttons; i++) {
    buttons[i].text = va_arg(ap, char *);
    buttons[i].id = va_arg(ap, int);
  }
  ....
}

When operator for(;; ) begin work, the 'nbuttons' variable still equal zero.


This suspicious code was found in Putty project by PVS-Studio static code analyzer.
Warning message is:
V621 Consider inspecting the 'for' operator. It's possible that the loop will be executed incorrectly or won't be executed at all. winctrls.c 310

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