Date: Thu, 31 Mar 2016 20:22:25 +0900 (JST) From: Shigeharu TAKENO <shige@iee.niit.ac.jp> To: freebsd-sparc64@freebsd.org Cc: Joerg Wunsch <joerg_wunsch@uriah.heep.sax.de> Subject: Re: /usr/bin/sort may be incorrect Message-ID: <201603311122.u2VBMPam007017@pc98tak.iee.niit.ac.jp> In-Reply-To: <20160331072303.GP53011@uriah.heep.sax.de> References: <201603250229.u2P2TVLp003567@pc98tak.iee.niit.ac.jp> <201603310446.u2V4kLGM003303@pc98tak.iee.niit.ac.jp> <20160331072303.GP53011@uriah.heep.sax.de>
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shige 03/31 2016
----------------
Thank you for your reply.
Joerg Wunsch wrote:
| struct key_value
| {
| struct bwstring *k;
| struct key_hint hint[];
| };
|
| If that works for you, too, I think it would be the preferrable way to
| write it.
Unfortunately this does not fix the problem.
| > The k field of key_value may be overwritten by the hint field
| > in numcoll_impl(), gnumcoll() and monthcoll() (coll.c), and the
| > pointer value of k may change to incorrect value.
|
| Are you saying that something like
|
| struct key_value *kw;
|
| ...
|
| kw->hint[-1] = something;
|
| happens? That would certainly be a bug in the code then that ought to
| be fixed, rather than worked around.
I tested under your suggestion "struct key_hint hint[]", which
behaves as the same of default sort command.
% ( echo 2 5 8 ; echo 2 6 5 ) | sort -n +0 -1 +1 -2 +2 -3
In key_coll(struct keys_array *ps1, struct keys_array *ps2,
size_t offset) (in coll.c), initial pointer values are the
followings:
&(ps1->key[0]) = 0x40c140f8
&(ps1->key[1]) = 0x40c14100
&(ps1->key[2]) = 0x40c14108
&(ps2->key[0]) = 0x40c14088
&(ps2->key[1]) = 0x40c14090
&(ps2->key[2]) = 0x40c14198
(the pointer repeat is only 8 byte.)
ps1->key[0].k = 0x40c060e0
ps1->key[1].k = 0x40c060f0
ps1->key[2].k = 0x40c06100
ps2->key[0].k = 0x40c060a0
ps2->key[1].k = 0x40c060b0
ps2->key[2].k = 0x40c060c0
key_coll() calls sm->func() = numcoll(), and it uses
numcoll_impl(struct key_value *kv1, struct key_value *kv2) with
ps1->key[i] and ps2->key[i]. The function numcoll_impl() uses k
field and hint field of struct key_value.
For i = 0, the k field pointers of arguments kv1 and kv2 of
numcoll_impl() are correct:
kv1->k = 0x40c060e0, kv2->k = 0x40c060a0
but the hint field pointers of kv1, kv2 are doughtful:
&(kv1->hint) = 0x40c14100, &(kv2->hint) = 0x40c14090
which are the same value of &(ps1->key[1]) and &(ps2->key[1]).
And for i = 1, the k field pointers of arguments kv1 and kv2
become incorrect:
kv1->k = 0x140c060f0, kv2->k = 0x140c060b0
which are added 0x100000000 to the original pointer value.
The sort command stops where it uses the value.
If we use the definition "struct key_hint hint[1]", the repeat
of pointers of ps1->key[i] becomes 32 byte, and incorrect changes
of pointers do not occur.
&(ps1->key[0]) = 0x40c08208
&(ps1->key[1]) = 0x40c08228
&(ps1->key[2]) = 0x40c08248
+========================================================+
Shigeharu TAKENO NIigata Institute of Technology
kashiwazaki,Niigata 945-1195 JAPAN
shige@iee.niit.ac.jp TEL(&FAX): +81-257-22-8161
+========================================================+
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