On Mon, Sep 23, 2019 at 09:16:26PM +0200, Johannes Sixt wrote: > Am 23.09.19 um 10:37 schrieb SZEDER Gábor: > > On Sun, Sep 22, 2019 at 11:01:26PM +0200, Johannes Sixt wrote: > >> Huh? For signed cutoff and positive CUTOFF_DATE_SLOP, > >> cutoff - CUTOFF_DATE_SLOP < cutoff is ALWAYS true. Signed interger > >> underflow is undefined behavior and signed integer arithmetic does not > >> wrap around! > >> > >> IOW, the new condition makes only sense today, because cutoff is an > >> unsigned type, but breaks down should we switch to a signed type. > > > > Yeah, that's what I meant with worrying about signed underflow in the > > commit message. As long as the cutoff is at least a day later than > > the minimum value of our future signed 'timestamp_t', the condition > > does the right thing. And considering that oldest time a signed 64 > > bit timestamp can represent far exceeds the age of the universe, and > > the oldest value of even a signed 32 bit timestamp is almost half the > > age of the Earth, I wasn't too worried. > > Note that commits and timestamps can be forged easily. I'm not worried > that Git does not work "correctly" with forged timestamps (as long as it > is not exploitable); but when it is simple to make foolproof, we should > do it. > > BTW, 32-bit timestamps cover just ~135 years (not half the age of > Earth). Gah, forgot the division with seconds/year when calculating the range of the 32bit timestamp. > That's too little for people who want to store historic > documents in a Git repository. Indeed, but 'timestamp_t' is defined as 'uintmax_t', and we have the Makefile knob 'NO_UINTMAX_T', in which case 'uintmax_t' is defined as 'uint32_t'...
