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bug#53696: Integer overflow on Guix GC size calculation
From: |
Bengt Richter |
Subject: |
bug#53696: Integer overflow on Guix GC size calculation |
Date: |
Wed, 2 Feb 2022 13:04:41 +0100 |
User-agent: |
Mutt/1.10.1 (2018-07-13) |
Hi Maxime, Ekaitz, et al,
On +2022-02-02 11:05:31 +0100, Maxime Devos wrote:
> Ekaitz Zarraga schreef op di 01-02-2022 om 14:06 [+0000]:
> > [17592186042897 MiB] deleting
> > '/gnu/store/wbz6vkiz7cq8c531xvb31lxm28nz332i-ghc-8.10.7'
>
> For comparison, this is about 16 exbibyte.
> According to <https://en.wikipedia.org/wiki/Byte#Multiple-byte_units>,
> that's more than the global monthly Internet traffic in 2004.
>
> According to <https://what-if.xkcd.com/31/>, 16 exbibyte would be about
> 17 million solid-state disks. Even though this ignores deduplication,
> this seems rather expensive.
>
> My guess is that the size of a store item was misrecorded somewhere.
>
> Greetings,
> Maxime.
s/misrecorded/mis-defined-in-record/ ?
Wild guessing follows:
--8<---------------cut here---------------start------------->8---
$ guile --no-auto-compile -c '(use-modules (ice-9 format))(format #t
"~20x\n~20x\n~20d\n" (* 17592186042897 (expt 2 20)) #xa1100000 #xa1100000)';
ffffffffa1100000
a1100000
2702180352
--8<---------------cut here---------------end--------------->8---
It looks to me like a 32-bit unsigned int should have been turned to 64-bit
unsigned long or bigint
but somehow got cast/interpreted as signed, becoming signed 64-bit long,
which then in turn was seen by the print as 64-bit unsigned long.
I don't know, but if records are being used, perhaps some slot integer-widening
logic
might be involved? Or a mis-defined int slot that should have been long to
accomodate
big > 31-bit positive integers?
Just guessing wildly -- I think I saw something about records and defining
their fields
as fixed C ints or longs.
--
Regards,
Bengt Richter
bug#53696: Integer overflow on Guix GC size calculation, Maxime Devos, 2022/02/02
- bug#53696: Integer overflow on Guix GC size calculation,
Bengt Richter <=
- bug#53696: Integer overflow on Guix GC size calculation, Bengt Richter, 2022/02/02
- bug#53696: Integer overflow on Guix GC size calculation, Ludovic Courtès, 2022/02/08
- bug#53696: Integer overflow on Guix GC size calculation, Ekaitz Zarraga, 2022/02/08
- bug#53696: Integer overflow on Guix GC size calculation, Ludovic Courtès, 2022/02/10
- bug#53696: Integer overflow on Guix GC size calculation, Ekaitz Zarraga, 2022/02/10