I have dug deeper into understanding what happens with both versions (method 1
& 2).
If the divisor has a high bit set, then pre[2] is not initialized inside
mpn_mod_1_1p_cps(), but it is also not used inside mpn_mod_1_1p() as there are
no leading zeroes.
In the other scenario, if the high
> Looking at mpn/generic/mod_1_1.c,
> if MOD_1_1P_METHOD == 1, the value[2] in the array is always set and always
> used;
> if MOD_1_1P_METHOD == 2, the value[2] is set only if cnt!=0, and it is used
> only if cnt!=0.
> There are also some assembler code implementations, each one with its
Ciao,
31 ago 2023, 18:06 da vinc...@vinc17.net:
> I don't think that this is sufficient for the test.
> The code Brett mentioned is for MOD_1_1P_METHOD = 2.
>
The code Brett mentioned is mixed, I fear.
Looking at mpn/generic/mod_1_1.c,if MOD_1_1P_METHOD == 1, the value[2] in the
array is
On 2023-08-31 17:03:12 +0200, marco.bodr...@tutanota.com wrote:
> Ciao,
>
> 31 ago 2023, 16:30 da ku...@shaw.ca:
>
> > 1) Edit line 248 mpn/generic/mp_limb_t pre[4]; into:
> >
> ~/src/gmp$ hg diff mpn/generic/
> diff -r 3ac5afa36be5 mpn/generic/mod_1.c
> --- a/mpn/generic/mod_1.c Wed Nov
Ciao,
31 ago 2023, 16:30 da ku...@shaw.ca:
> 1) Edit line 248 mpn/generic/mp_limb_t pre[4]; into:
>
~/src/gmp$ hg diff mpn/generic/
diff -r 3ac5afa36be5 mpn/generic/mod_1.c
--- a/mpn/generic/mod_1.c Wed Nov 02 13:48:37 2022 +0100
+++ b/mpn/generic/mod_1.c Thu Aug 31 16:46:35 2023
Brett Kuntz writes:
Go to line 248 inside mpn/generic/mod_1.c
mp_limb_t pre[4];
There is no such thing on an unedited version of GMP 6.3, not on line
248 not anyplace else in that file.
mpn_mod_1_1p_cps (pre, b);
Only initializes pre[0], pre[1], and pre[3]. ***NOT*** pre[2].
> It does not exist, only pre[0] through pre[3] does.
pre[4] **IS** pre[0] through pre[3]
Go to line 248 inside mpn/generic/mod_1.c
mp_limb_t pre[4];
That is NOT initialized.
The next line:
mpn_mod_1_1p_cps (pre, b);
Only initializes pre[0], pre[1], and pre[3]. ***NOT*** pre[2].
Brett Kuntz writes:
Take a look at function mpn_mod_1() in /mpn/generic/ mod_1.c on lines 248 -
250
mp_limb_t pre[4];
mpn_mod_1_1p_cps (pre, b);
mp_limb_t pre[4] is not initialized
It does not exist, only pre[0] through pre[3] does.
and the mpn_mod_1_1p_cps() function
never
Hello, today I found a bug in the latest GMP (6.3) using uninitialized memory
in /mpn/generic/mod_1_1.c while trying to understand some functions like
mpn_mod_1_1p_cps.
Take a look at function mpn_mod_1() in /mpn/generic/ mod_1.c on lines 248 - 250
mp_limb_t pre[4];
mpn_mod_1_1p_cps (pre, b);
