libc {
  GLIBC_2.1 {
    # functions used in other libraries
    __backtrace; __backtrace_symbols; __backtrace_symbols_fd;

    # b*
    backtrace; backtrace_symbols; backtrace_symbols_fd;
  }
  GLIBC_2.2 {
    # These are to support some gcc features.
    __cyg_profile_func_enter; __cyg_profile_func_exit;
  }
  GLIBC_2.3.4 {
    __chk_fail;
    __memcpy_chk; __memmove_chk; __mempcpy_chk; __memset_chk; __stpcpy_chk;
    __strcat_chk; __strcpy_chk; __strncat_chk; __strncpy_chk;
    __sprintf_chk; __vsprintf_chk; __snprintf_chk; __vsnprintf_chk;
    __printf_chk; __fprintf_chk; __vprintf_chk; __vfprintf_chk;
    __gets_chk;
  }
}