Re: [bug #23996] arithmetic overflow when using -used

[James Youngman]

On Mon, Sep 1, 2008 at 2:11 AM, James Youngman <address@hidden> wrote:
> On Sun, Aug 24, 2008 at 12:01 AM, Andreas Schwab <address@hidden> wrote:
>> A good compiler (like gcc 4.3) will optimize this to 0, effectively
>> removing the overflow check.  Checking for overflow after the fact is
>> not possible in C.
>
> I'd welcome an alternative patch for the subtraction operation.

Well, in the absence of an alternative patch I propose to go with the
one attached to the bug (after correcting the bug number). Making a
patch which never overflows is nontrivial anyway, since the C standard
leaves unspecified whether time_t is signed or not, and provides no
macro specifying its maximum and minimum values (partly because, I
assume, the implementation is not guaranteed to be able to correctly
handle them).

James.