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Re: [bug-gawk] Occasional overflow with gmp
From: |
Andrew J. Schorr |
Subject: |
Re: [bug-gawk] Occasional overflow with gmp |
Date: |
Sun, 20 Oct 2019 10:17:54 -0400 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Sat, Oct 19, 2019 at 04:18:24PM +1100, James Milne wrote:
> This crashes:
>
> > echo '' | awk -M '{print 200000000000000000000000000000000000000000 *
> 200000000000000000000000000000000000000000 ^ 2000000000000000000}'
>
> > gmp: overflow in mpz type
> > breaking.awk: line 3: 197234 Done echo ''
> > 197235 Aborted (core dumped) | awk -M '{print
> 200000000000000000000000000000000000000000 *
> 200000000000000000000000000000000000000000 ^ 2000000000000000000}'
>
>
> Should be noted the crash is a slightly smaller number than the larger.
Here's a simpler example that crashes:
./gawk -M 'BEGIN {print 200000000000000000000000000000000000000000 ^
2000000000}'
gmp: overflow in mpz type
Abort (core dumped)
And here's the backtrace:
(gdb) bt
#0 0x00007ffff6c20337 in raise () from /lib64/libc.so.6
#1 0x00007ffff6c21a28 in abort () from /lib64/libc.so.6
#2 0x00007ffff74deffc in __gmpz_realloc () from /lib64/libgmp.so.10
#3 0x00007ffff74dc711 in __gmpz_n_pow_ui () from /lib64/libgmp.so.10
#4 0x00000000004571fa in mpg_pow (t1=t1@entry=0x6c1930, t2=t2@entry=0x6c19e0)
at mpfr.c:1413
#5 0x00000000004575f6 in mpg_interpret (cp=0x7fffffffd840) at mpfr.c:1567
#6 0x00000000004401cb in h_interpret (code=<optimized out>) at interpret.h:97
#7 0x0000000000407df8 in main (argc=3, argv=0x7fffffffdab8) at main.c:522
Here's mpfr.c:mpg_pow():
static NODE *
mpg_pow(NODE *t1, NODE *t2)
{
NODE *r;
int tval;
if (is_mpg_integer(t1) && is_mpg_integer(t2)) {
if (mpz_sgn(t2->mpg_i) >= 0 && mpz_fits_ulong_p(t2->mpg_i)) {
r = mpg_integer();
mpz_pow_ui(r->mpg_i, t1->mpg_i, mpz_get_ui(t2->mpg_i));
} else {
mpfr_ptr p1, p2;
p1 = MP_FLOAT(t1);
p2 = MP_FLOAT(t2);
r = mpg_float();
tval = mpfr_pow(r->mpg_numbr, p1, p2, ROUND_MODE);
IEEE_FMT(r->mpg_numbr, tval);
}
} else {
r = mpg_float();
if (is_mpg_integer(t2))
tval = mpfr_pow_z(r->mpg_numbr, t1->mpg_numbr,
t2->mpg_i, ROUND_MODE);
else {
mpfr_ptr p1;
p1 = MP_FLOAT(t1);
tval = mpfr_pow(r->mpg_numbr, p1, t2->mpg_numbr,
ROUND_MODE);
}
IEEE_FMT(r->mpg_numbr, tval);
}
return r;
}
So it's crashing in the call to mpz_pow_ui(). It seems that it's either an
issue with the gmp library's implementation of mpz_pow_ui(), or we are somehow
calling it incorrectly.
There's a similar issue reported for julia here:
https://github.com/JuliaLang/julia/issues/15293
And that example also crashes with gawk:
./gawk -M 'BEGIN {print 2^ 233423411231}'
gmp: overflow in mpz type
Abort (core dumped)
So it does seem like a gmp issue.
Regards,
Andy