Bug#973620: bash: overflow on integer variables greater than 9223372036854775807

[Gioele Barabucci]

Control: found -1 5.2.21-2
Control: tags -1 upstream
X-Debbugs-CC: bug-bash@gnu.org

On Mon, 2 Nov 2020 16:46:14 +0100 Antonio <antdev66@gmail.com> wrote:
> Dear Maintainer,
> recently while I was running some tests, I ran into this strange overflow:
>
> $ declare -i n=9223372036854775800; for((i=0; i<15; ++i)); do echo "$i -> $n";
> n+=1; done
>
> 0 -> 9223372036854775800
> 1 -> 9223372036854775801
> 2 -> 9223372036854775802
> 3 -> 9223372036854775803
> 4 -> 9223372036854775804
> 5 -> 9223372036854775805
> 6 -> 9223372036854775806
> 7 -> 9223372036854775807
> 8 -> -9223372036854775808
> 9 -> -9223372036854775807
> 10 -> -9223372036854775806
> 11 -> -9223372036854775805
> 12 -> -9223372036854775804
> 13 -> -9223372036854775803
> 14 -> -9223372036854775802
>
> The integer handled by bash is obviously very large, but I believe
> that in the event of an overflow it would be better to reset the
> variable and issue an error flow warning, rather than remain silent.

Bash 5.2.21 is affected by this issue:

    $ declare -i n=$((2**63 - 2))
    $ for i in {1..4}; do echo "$i -> $n"; n+=1; done
    1 -> 9223372036854775806
    2 -> 9223372036854775807
    3 -> -9223372036854775808
    4 -> -9223372036854775807

    $ declare -i n=36893488147419103234; echo $?
    0
    $ echo $n
    2

Would it be possible to detect this overflow (or non-representable 
numbers, like in the second case) and warn about it?

Regards,

--
Gioele Barabucci