static int b_unpack (lua_State *L) {
  Header h;
  const char *fmt = luaL_checkstring(L, 1);
  size_t ld;
  const char *data = luaL_checklstring(L, 2, &ld);
  size_t pos = luaL_optinteger(L, 3, 1) - 1;
  defaultoptions(&h);
  lua_settop(L, 2);
  while (*fmt) {
    int opt = *fmt++;
    size_t size = optsize(L, opt, &fmt);
    pos += gettoalign(pos, &h, opt, size);
    luaL_argcheck(L, pos+size <= ld, 2, "data string too short");
    luaL_checkstack(L, 1, "too many results");
    switch (opt) {
      case 'b': case 'B': case 'h': case 'H':
      case 'l': case 'L': case 'T': case 'i':  case 'I': {  /* integer types */
        int issigned = islower(opt);
        lua_Number res = getinteger(data+pos, h.endian, issigned, size);
        lua_pushnumber(L, res);
        break;
      }
      case 'x': {
        break;
      }
      case 'f': {
        float f;
        memcpy(&f, data+pos, size);
        correctbytes((char *)&f, sizeof(f), h.endian);
        lua_pushnumber(L, f);
        break;
      }
      case 'd': {
        double d;
        memcpy(&d, data+pos, size);
        correctbytes((char *)&d, sizeof(d), h.endian);
        lua_pushnumber(L, d);
        break;
      }
      case 'c': {
        if (size == 0) {
          if (!lua_isnumber(L, -1))
            luaL_error(L, "format `c0' needs a previous size");
          size = lua_tonumber(L, -1);
          lua_pop(L, 1);
          luaL_argcheck(L, pos+size <= ld, 2, "data string too short");
        }
        lua_pushlstring(L, data+pos, size);
        break;
      }
      case 's': {
        const char *e = (const char *)memchr(data+pos, '\0', ld - pos);
        if (e == NULL)
          luaL_error(L, "unfinished string in data");
        size = (e - (data+pos)) + 1;
        lua_pushlstring(L, data+pos, size - 1);
        break;
      }
      default: controloptions(L, opt, &fmt, &h);
    }
    pos += size;
  }
  lua_pushinteger(L, pos + 1);
  return lua_gettop(L) - 2;
}
The software performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control.