Ján Jančár on Tue, 10 Jul 2018 18:35:43 +0200


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SIGSEGV on isprime 

Hi all,

While running pari on some grid computing machines I keep encountering
this mysterious error, which only happens when working on certain
machines and not on others.

To reproduce, I compiled the following:

> #include <pari/pari.h>
> #include <stdio.h>
> 
> int main(void) {
>         pari_init(1000000000, 1000000);
>         GEN order = strtoi("0x8d4731c77d346297e54306afea3730a1");
>         long i = isprime(order);
>         printf("%li\n", i);
>         pari_close();
>         return 0;
> }

with:
    gcc -o t test.c -lrt -lpari

on:
    Linux 3.16.0-5-amd64 #1 SMP Debian
    3.16.51-3+deb8u1+zs2 (2018-01-12) x86_64 GNU/Linux

where it run just fine.
However when run(and compiled) on:
    Linux 4.9.0-6-amd64 #1 SMP Debian
    4.9.82-1+deb9u3 (2018-03-02) x86_64 GNU/Linux

It SIGSEGVs in isprime():

> Program received signal SIGSEGV, Segmentation fault.
> 0x00002aaaab1f771c in red_montgomery (T=0x2aaae879e6a0, N=0x2aaae879efe0, inv=2796584439883844767) at ../src/kernel/gmp/mp.c:1013
> 1013	    while (Td < (GEN)av) { t = subllx(*++Td, *++Nd); *Td = t; }
> (gdb) bt
> #0  0x00002aaaab1f771c in red_montgomery (T=0x2aaae879e6a0, N=0x2aaae879efe0, inv=2796584439883844767) at ../src/kernel/gmp/mp.c:1013
> #1  0x00002aaaab33a0ac in _sqr_montred (E=0x2aaae879ef38, x=0x2aaae879e6d0) at ../src/basemath/arith1.c:3311
> #2  0x00002aaaab33a138 in _mul2_montred (E=0x2aaae879ef38, x=0x2aaae879e6d0) at ../src/basemath/arith1.c:3326
> #3  0x00002aaaab39d641 in gen_pow_fold_i (x=0x2aaae879eef0, N=0x2aaae879efa0, E=0x2aaae879ef38, sqr=0x2aaaab33a068 <_sqr_montred>, msqr=0x2aaaab33a10d <_mul2_montred>)
>     at ../src/basemath/bb_group.c:254
> #4  0x00002aaaab33abf3 in Fp_pow (A=0x2aaaabaa3998 <readonly_constants+56>, K=0x2aaae879efa0, N=0x2aaae879efe0) at ../src/basemath/arith1.c:3508
> #5  0x00002aaaab5ca498 in bad_for_base (S=0x7fffffffe210, a=0x2aaaabaa3998 <readonly_constants+56>) at ../src/basemath/prime.c:95
> #6  0x00002aaaab5cbaf2 in BPSW_psp (N=0x2aaae879efe0) at ../src/basemath/prime.c:570
> #7  0x00002aaaab5cca58 in isprime (x=0x2aaae879efe0) at ../src/basemath/prime.c:846
> #8  0x0000000000400788 in main ()
> (gdb) info locals
> __value = 8722076062158158581
> __arg1 = 144115188075855878
> __arg2 = 10180160215563133591
> __temp = 18446744073709551615
> av = 46913531930272
> Te = 0x2aaae867e688
> Td = 0x2aaae867e6a0
> Ne = 0x2aaae867efe8
> Nd = 0x2aaae867f000
> scratch = 0x2aaae867e680
> i = 2
> j = 2
> m = 9020403664262637533
> t = 8722076062158158581
> d = 4
> k = 2
> carry = 1
> hiremainder = 4978068440930021014
> overflow = 1
> (gdb) info args
> T = 0x2aaae867e6a0
> N = 0x2aaae867efe0
> inv = 2796584439883844767
> (gdb) quit

I compiled pari 2.9.5 / 2.10.1 / current git master, with
./Configure --enable-tls -g
and the error happens in all of the versions.

Any ideas on what might be causing this? ldd of the binary on both
machines shows the same libraries are used, so it is very mysterious to
me that it works on one and not on the other.

Cheers,
-- 
Jan
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