cmake.cpp

static const struct {
  DWORD   winerr;
  int     doserr;
} doserrors[] =
{
  ...
};

static void
la_dosmaperr(unsigned long e)
{
  ...
  for (i = 0; i < sizeof(doserrors); i++)
  {
    if (doserrors[i].winerr == e)
    {
      errno = doserrors[i].doserr;
      return;
    }
  }
  ...
}