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Deep recursion on subroutine #15

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darkblaze69 opened this issue Aug 4, 2023 · 2 comments
Open

Deep recursion on subroutine #15

darkblaze69 opened this issue Aug 4, 2023 · 2 comments

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@darkblaze69
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After upgrading from perl 5.36 to perl 5.38 I get this error:

$ ipcalc -r 172.18.10.32-172.18.10.33
deaggregate 172.18.10.32 - 172.18.10.33
Deep recursion on subroutine "Math::BigInt::bior" at /usr/share/perl5/core_perl/Math/BigFloat.pm line 3883.
Deep recursion on subroutine "Math::BigFloat::bior" at /usr/share/perl5/core_perl/Math/BigInt.pm line 3513.
@LeoVerto
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LeoVerto commented Oct 25, 2023 •
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This appears to be caused by a change to bitshift operations in Math::BigInt included in 5.38 causing the deaggregate function in https://github.com/kjokjo/ipcalc/blob/master/ipcalc#L694 to loop forever.

See https://rt.cpan.org/Public/Bug/Display.html?id=149932 and Perl/perl5#21518

Actually this happens due to a different bug when comparing BigInts to BigFloats, which was first introduced in Math:BigInt 1.999840 and fixed in 1.999842.

In 2022 another bug in bitwise comparisons had already broken ipcalc, also causing an infinite recursion (Debian bug, CPAN bug) but was fixed in 1.999838.

LeoVerto added a commit to LeoVerto/ipcalc that referenced this issue Oct 25, 2023
@LeoVerto
Fix deaggregate failing on perl 5.38
2b6c1b7 
Workaround for a bug causing an infinite loop when comparing a
BigInt to a BigFloat, introduced in Math::BigInt 1.999840 and
fixed in 1.999842.

See pjacklam/p5-Math-BigInt@d268562

Fixes kjokjo#15, fixes kjokjo#17.
LeoVerto added a commit to LeoVerto/ipcalc that referenced this issue Oct 25, 2023
@LeoVerto
Fix deaggregate failing on perl 5.38
4c8a2ea 
Workaround for a bug causing an infinite recursion when comparing
a BigInt to a BigFloat, introduced in Math::BigInt 1.999840 and
fixed in 1.999842.

See pjacklam/p5-Math-BigInt@d268562

Fixes kjokjo#15, fixes kjokjo#17.
@pjacklam
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pjacklam commented Dec 2, 2023

I don’t know the inner workings of the ipcalc utility, but if it is possible, I recommend using bigint or bigfloat instead of bignum. If you are doing integer arithmetic only, then use bigint. If you need floating point numbers, then use bigfloat.

The bignum module does automatic upgrading and downgrading between Math::BigInt and Math::BigFloat. Not only does this introduce overhead, but the upgrading and downgrading has never been fully implemented. I have tried to finish what the original author never completed, but unfortunately, there have been some hiccups along the way.

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@pjacklam @LeoVerto @darkblaze69