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* BUG #18248: Expression is always zero
@ 2023-12-14 05:32 PG Bug reporting form <noreply@postgresql.org>
2023-12-14 11:08 ` Re: BUG #18248: Expression is always zero Laurenz Albe <laurenz.albe@cybertec.at>
2023-12-14 11:10 ` Re: BUG #18248: Expression is always zero Julien Rouhaud <rjuju123@gmail.com>
2023-12-14 11:11 ` Re: BUG #18248: Expression is always zero Alexander Lakhin <exclusion@gmail.com>
0 siblings, 3 replies; 5+ messages in thread
From: PG Bug reporting form @ 2023-12-14 05:32 UTC (permalink / raw)
To: pgsql-bugs@lists.postgresql.org; +Cc: rekgrpth@gmail.com
The following bug has been logged on the website:
Bug reference: 18248
Logged by: RekGRpth
Email address: rekgrpth@gmail.com
PostgreSQL version: 16.1
Operating system: docker alpine
Description:
The value of expression 'thistimecnt >> 31 >> 31 >> 2' (in
src/timezone/zic.c) is zero regardless of the value of the left operand
'thistimecnt', because it is shifted by 64 (in total) bits, which is greater
or equal to its size of 64 bits.
Maybe this was what was meant?
thistimecnt >> 31 >> 2
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: BUG #18248: Expression is always zero
2023-12-14 05:32 BUG #18248: Expression is always zero PG Bug reporting form <noreply@postgresql.org>
@ 2023-12-14 11:08 ` Laurenz Albe <laurenz.albe@cybertec.at>
2 siblings, 0 replies; 5+ messages in thread
From: Laurenz Albe @ 2023-12-14 11:08 UTC (permalink / raw)
To: rekgrpth@gmail.com; pgsql-bugs@lists.postgresql.org
On Thu, 2023-12-14 at 05:32 +0000, PG Bug reporting form wrote:
> The value of expression 'thistimecnt >> 31 >> 31 >> 2' (in
> src/timezone/zic.c) is zero regardless of the value of the left operand
> 'thistimecnt', because it is shifted by 64 (in total) bits, which is greater
> or equal to its size of 64 bits.
>
> Maybe this was what was meant?
> thistimecnt >> 31 >> 2
This code is just taken from the GNU C library, and it's in our interest to
keep it as much aligned with upstram code as possible.
Yours,
Laurenz Albe
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: BUG #18248: Expression is always zero
2023-12-14 05:32 BUG #18248: Expression is always zero PG Bug reporting form <noreply@postgresql.org>
@ 2023-12-14 11:10 ` Julien Rouhaud <rjuju123@gmail.com>
2023-12-14 14:40 ` Re: BUG #18248: Expression is always zero Tom Lane <tgl@sss.pgh.pa.us>
2 siblings, 1 reply; 5+ messages in thread
From: Julien Rouhaud @ 2023-12-14 11:10 UTC (permalink / raw)
To: rekgrpth@gmail.com; pgsql-bugs@lists.postgresql.org
Hi,
On Thu, Dec 14, 2023 at 05:32:49AM +0000, PG Bug reporting form wrote:
>
> The value of expression 'thistimecnt >> 31 >> 31 >> 2' (in
> src/timezone/zic.c) is zero regardless of the value of the left operand
> 'thistimecnt', because it is shifted by 64 (in total) bits, which is greater
> or equal to its size of 64 bits.
>
> Maybe this was what was meant?
> thistimecnt >> 31 >> 2
Note that this is code imported as-is from upstream IANA tzcode, so we wouldn't
make any change ourself.
Looking at their git history they added it to remove some theoretical int
limits:
https://github.com/eggert/tz/commit/cc8aec6ecb1ecc3099f173e2bca9785ae8359c03
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: BUG #18248: Expression is always zero
2023-12-14 05:32 BUG #18248: Expression is always zero PG Bug reporting form <noreply@postgresql.org>
2023-12-14 11:10 ` Re: BUG #18248: Expression is always zero Julien Rouhaud <rjuju123@gmail.com>
@ 2023-12-14 14:40 ` Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 0 replies; 5+ messages in thread
From: Tom Lane @ 2023-12-14 14:40 UTC (permalink / raw)
To: Julien Rouhaud <rjuju123@gmail.com>; +Cc: rekgrpth@gmail.com; pgsql-bugs@lists.postgresql.org
Julien Rouhaud <rjuju123@gmail.com> writes:
> On Thu, Dec 14, 2023 at 05:32:49AM +0000, PG Bug reporting form wrote:
>> The value of expression 'thistimecnt >> 31 >> 31 >> 2' (in
>> src/timezone/zic.c) is zero regardless of the value of the left operand
> Note that this is code imported as-is from upstream IANA tzcode, so we wouldn't
> make any change ourself.
> Looking at their git history they added it to remove some theoretical int
> limits:
> https://github.com/eggert/tz/commit/cc8aec6ecb1ecc3099f173e2bca9785ae8359c03
Yeah, the tzcode crew have a wider range of (possibly theoretical)
target systems in mind than we do. They probably won't think this
is a bug, and we're unlikely to diverge from whatever they do.
regards, tom lane
^ permalink raw reply [nested|flat] 5+ messages in thread
* Re: BUG #18248: Expression is always zero
2023-12-14 05:32 BUG #18248: Expression is always zero PG Bug reporting form <noreply@postgresql.org>
@ 2023-12-14 11:11 ` Alexander Lakhin <exclusion@gmail.com>
2 siblings, 0 replies; 5+ messages in thread
From: Alexander Lakhin @ 2023-12-14 11:11 UTC (permalink / raw)
To: rekgrpth@gmail.com; pgsql-bugs@lists.postgresql.org
Hello Georgy,
14.12.2023 08:32, PG Bug reporting form wrote:
> The following bug has been logged on the website:
>
> Bug reference: 18248
> Logged by: RekGRpth
> Email address: rekgrpth@gmail.com
>
> The value of expression 'thistimecnt >> 31 >> 31 >> 2' (in
> src/timezone/zic.c) is zero regardless of the value of the left operand
> 'thistimecnt', because it is shifted by 64 (in total) bits, which is greater
> or equal to its size of 64 bits.
>
> Maybe this was what was meant?
> thistimecnt >> 31 >> 2
I see the same in
https://github.com/eggert/tz/blob/main/zic.c
So maybe you would like to report that to the tz mailing list?:
https://www.iana.org/time-zones
Best regards,
Alexander
^ permalink raw reply [nested|flat] 5+ messages in thread
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2023-12-14 05:32 BUG #18248: Expression is always zero PG Bug reporting form <noreply@postgresql.org>
2023-12-14 11:08 ` Laurenz Albe <laurenz.albe@cybertec.at>
2023-12-14 11:10 ` Julien Rouhaud <rjuju123@gmail.com>
2023-12-14 14:40 ` Tom Lane <tgl@sss.pgh.pa.us>
2023-12-14 11:11 ` Alexander Lakhin <exclusion@gmail.com>
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