This is a discussion on Re: time_t remarks - Openssl ; On Thu, Dec 29, 2005 at 02:44:18PM +0100, Peter Sylvester wrote: > > I saw in the lastest snapshots that in the ssl library the fundction > time has been casted to an unsigned long. > This seems to be ...
On Thu, Dec 29, 2005 at 02:44:18PM +0100, Peter Sylvester wrote:
> I saw in the lastest snapshots that in the ssl library the fundction
> time has been casted to an unsigned long.
> This seems to be some hack to cover the 2038 problem on 32 bit machines.
> I am not sure
> whether the attempted solution is good:
> As far as I see the only usage is to determine whether a timeout has
> occured. How much can a
> session last? More than 20 years? If not, I think one should define a
> notion of epoch which
> covers the problem that it seems to be undefined whether in 2038 the
> value goes to 0 or to
> a large negative value depending on the implementation. I.e.
> the time is also initialized with time(NULL)|x3fffffff
> and in ssl_sess.c
> if (ret->time+ter->timeout < (time(NULL) | x7fffffff)
> and similar in ssl_bio etc.
The proper way to do a check for a timeout is:
time(NULL) - ret->time > ter->timeout
Or something simular, the important part is the substraction of
the 2 time variables.
This will avoid any problems you have with overflows. If
time(NULL) has overflown, the substraction of time(NULL) with
ret->time will still give a positive number.
PS: Depending on the platform, time_t can be signed or unsigned.
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