Math::BigInt weirdness

zude has asked for the wisdom of the Perl Monks concerning the following question:

Hi guys and gals, noticed a strange behaviour while working on some public key crypto routines, which I am able to reproduce as follows:

use Math::BigInt;

my $E = new Math::BigInt "0xE01AFC76F0814D";
my $D = new Math::BigInt "0x956752E5F9DC53";
my $m = new Math::BigInt 2;

$m->bmodpow($D, $E) while 1;
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Now if I let this cook for a while, eventually certain other programs will begin to segfault:

$ man perl 
groff: troff: segmentation fault
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ps doesn't show anything strange, like perl consuming 800MB of memory... nothing is swapping... system is not unduly slow... but if I kill or even just suspend the script, the segfaults stop happening.

I don't even understand the mechanism that could force another process to segfault, much less how to fix it. Ideas?

Thanks

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Re: Math::BigInt weirdness by Abigail-II (Bishop) on May 10, 2004 at 21:59 UTC
That shouldn't happen, but it's hard to say who's to blame. I can't reproduce it. What OS are you using? What version of Perl? Can you trace the segfaulting program and determine why it's segfaulting? Abigail	[reply]
Re: Math::BigInt weirdness by hv (Prior) on May 11, 2004 at 01:45 UTC
I had an intermittent problem like that a while back, which turned out to be CPU overheating due to death of fan. I think this is unlikely to be due to something somehow randomly overwriting memory - Unix systems simply don't work like that unless you're doing stuff in kernel space. Hugo	[reply]
Re: Math::BigInt weirdness by Joost (Canon) on May 10, 2004 at 22:01 UTC
Hmmmm... I'm running that code as I'm typing this, but nothing strange is happening over here - Linux 2.4.20-4GB-athlon #1 Fri Mar 12 15:34:26 UTC 2004 i686 unknown unknown GNU/Linux w/ perl, v5.8.4 built for i686-linux. Except ofcourse that it takes up about 92 % of my CPU time. :-) What OS are you running? "What should it profit a man, if he should win a flame war, yet lose his cool?"	[reply]
Re: Re: Math::BigInt weirdness by zude (Scribe) on May 11, 2004 at 00:54 UTC
Thanks for replies. This is happening on staging server with RH7.3+patches, kernel 2.4.20-4/perl 5.6.1. Don't want to mess with the config too much because then I have to port it to all the production servers. Anyway glad it doesn't reproduce, guess I'll dig in some more...	[reply]


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