From: Richard Biener <richard.guenther@gmail.com>
To: Jeff Law <law@redhat.com>
Cc: "Martin Liška" <mliska@suse.cz>,
"Jakub Jelinek" <jakub@redhat.com>,
"Alexander Monakov" <amonakov@ispras.ru>,
"GCC Patches" <gcc-patches@gcc.gnu.org>,
"Nathan Sidwell" <nathan@acm.org>,
"Jason Merrill" <jason@redhat.com>,
"Paul Richard Thomas" <paul.richard.thomas@gmail.com>,
"Martin Jambor" <mjambor@suse.cz>
Subject: Re: [PATCH][RFC] Sanitize equals and hash functions in hash-tables.
Date: Tue, 21 May 2019 09:38:00 -0000 [thread overview]
Message-ID: <CAFiYyc1oRW5_qrQ3=DDK5SqD7XhKo7X8-AApXyKgQ2xs3mWgcg@mail.gmail.com> (raw)
In-Reply-To: <be20f9e6-0de7-58f2-e668-62727274fb4e@redhat.com>
On Tue, May 21, 2019 at 12:07 AM Jeff Law <law@redhat.com> wrote:
>
> On 5/13/19 1:41 AM, Martin Liška wrote:
> > On 11/8/18 9:56 AM, Martin Liška wrote:
> >> On 11/7/18 11:23 PM, Jeff Law wrote:
> >>> On 10/30/18 6:28 AM, Martin Liška wrote:
> >>>> On 10/30/18 11:03 AM, Jakub Jelinek wrote:
> >>>>> On Mon, Oct 29, 2018 at 04:14:21PM +0100, Martin Liška wrote:
> >>>>>> +hashtab_chk_error ()
> >>>>>> +{
> >>>>>> + fprintf (stderr, "hash table checking failed: "
> >>>>>> + "equal operator returns true for a pair "
> >>>>>> + "of values with a different hash value");
> >>>>> BTW, either use internal_error here, or at least if using fprintf
> >>>>> terminate with \n, in your recent mail I saw:
> >>>>> ...different hash valueduring RTL pass: vartrack
> >>>>> ^^^^^^
> >>>> Sure, fixed in attached patch.
> >>>>
> >>>> Martin
> >>>>
> >>>>>> + gcc_unreachable ();
> >>>>>> +}
> >>>>> Jakub
> >>>>>
> >>>> 0001-Sanitize-equals-and-hash-functions-in-hash-tables.patch
> >>>>
> >>>> From 0d9c979c845580a98767b83c099053d36eb49bb9 Mon Sep 17 00:00:00 2001
> >>>> From: marxin <mliska@suse.cz>
> >>>> Date: Mon, 29 Oct 2018 09:38:21 +0100
> >>>> Subject: [PATCH] Sanitize equals and hash functions in hash-tables.
> >>>>
> >>>> ---
> >>>> gcc/hash-table.h | 40 +++++++++++++++++++++++++++++++++++++++-
> >>>> 1 file changed, 39 insertions(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/gcc/hash-table.h b/gcc/hash-table.h
> >>>> index bd83345c7b8..694eedfc4be 100644
> >>>> --- a/gcc/hash-table.h
> >>>> +++ b/gcc/hash-table.h
> >>>> @@ -503,6 +503,7 @@ private:
> >>>>
> >>>> value_type *alloc_entries (size_t n CXX_MEM_STAT_INFO) const;
> >>>> value_type *find_empty_slot_for_expand (hashval_t);
> >>>> + void verify (const compare_type &comparable, hashval_t hash);
> >>>> bool too_empty_p (unsigned int);
> >>>> void expand ();
> >>>> static bool is_deleted (value_type &v)
> >>>> @@ -882,8 +883,12 @@ hash_table<Descriptor, Allocator>
> >>>> if (insert == INSERT && m_size * 3 <= m_n_elements * 4)
> >>>> expand ();
> >>>>
> >>>> - m_searches++;
> >>>> +#if ENABLE_EXTRA_CHECKING
> >>>> + if (insert == INSERT)
> >>>> + verify (comparable, hash);
> >>>> +#endif
> >>>>
> >>>> + m_searches++;
> >>>> value_type *first_deleted_slot = NULL;
> >>>> hashval_t index = hash_table_mod1 (hash, m_size_prime_index);
> >>>> hashval_t hash2 = hash_table_mod2 (hash, m_size_prime_index);
> >>>> @@ -930,6 +935,39 @@ hash_table<Descriptor, Allocator>
> >>>> return &m_entries[index];
> >>>> }
> >>>>
> >>>> +#if ENABLE_EXTRA_CHECKING
> >>>> +
> >>>> +/* Report a hash table checking error. */
> >>>> +
> >>>> +ATTRIBUTE_NORETURN ATTRIBUTE_COLD
> >>>> +static void
> >>>> +hashtab_chk_error ()
> >>>> +{
> >>>> + fprintf (stderr, "hash table checking failed: "
> >>>> + "equal operator returns true for a pair "
> >>>> + "of values with a different hash value\n");
> >>>> + gcc_unreachable ();
> >>>> +}
> >>> I think an internal_error here is probably still better than a simple
> >>> fprintf, even if the fprintf is terminated with a \n :-)
> >> Fully agree with that, but I see a lot of build errors when using internal_error.
> >>
> >>> The question then becomes can we bootstrap with this stuff enabled and
> >>> if not, are we likely to soon? It'd be a shame to put it into
> >>> EXTRA_CHECKING, but then not be able to really use EXTRA_CHECKING
> >>> because we've got too many bugs to fix.
> >> Unfortunately it's blocked with these 2 PRs:
> >> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87845
> >> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87847
> > Hi.
> >
> > I've just added one more PR:
> > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90450
> >
> > I'm sending updated version of the patch that provides a disablement for the 3 PRs
> > with a new function disable_sanitize_eq_and_hash.
> >
> > With that I can bootstrap and finish tests. However, I've done that with a patch
> > limits maximal number of checks:
> So rather than call the disable_sanitize_eq_and_hash, can you have its
> state set up when you instantiate the object? It's not a huge deal,
> just thinking about loud.
>
>
>
> So how do we want to go forward, particularly the EXTRA_EXTRA checking
> issue :-)
There is at least one PR where we have a table where elements _in_ the
table are never compared against each other but always against another
object (I guess that's usual even), but the setup is in a way that the
comparison function only works with those. With the patch we verify
hashing/comparison for something that is never used.
So - wouldn't it be more "correct" to only verify comparison/hashing
at lookup time, using the object from the lookup and verify that against
all other elements?
Richard.
>
> Jeff
next prev parent reply other threads:[~2019-05-21 9:38 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-29 12:02 Martin Liška
2018-10-29 14:28 ` Alexander Monakov
2018-10-29 15:56 ` Martin Liška
2018-10-30 10:32 ` Jakub Jelinek
2018-10-30 14:17 ` Martin Liška
2018-11-07 22:24 ` Jeff Law
2018-11-07 22:44 ` Jakub Jelinek
2018-11-08 8:56 ` Martin Liška
2019-05-13 7:42 ` Martin Liška
2019-05-20 17:26 ` Jason Merrill
2019-05-20 22:07 ` Jeff Law
2019-05-21 9:38 ` Richard Biener [this message]
2019-05-21 11:02 ` Martin Liška
2019-05-21 11:52 ` Richard Biener
2019-05-22 9:13 ` Martin Liška
2019-05-31 13:23 ` Richard Biener
2019-05-31 13:35 ` Martin Liška
2019-05-31 22:10 ` Jeff Law
2019-06-03 13:35 ` Martin Liška
2019-06-07 8:57 ` Richard Biener
2019-06-07 12:04 ` Martin Liška
2019-06-07 12:09 ` Richard Biener
2019-06-07 12:13 ` Martin Liška
2019-06-07 14:48 ` Martin Sebor
2019-06-07 21:43 ` Jason Merrill
2019-06-10 7:08 ` Martin Liška
2019-06-10 18:22 ` Jason Merrill
2019-06-11 7:41 ` Martin Liška
2019-06-11 12:28 ` Jason Merrill
2019-06-11 13:16 ` Martin Liška
2019-06-11 19:02 ` Jason Merrill
2019-06-12 7:59 ` Richard Biener
2019-06-12 8:02 ` Martin Liška
2019-06-12 9:15 ` Martin Liška
2019-06-12 9:41 ` Richard Biener
2019-06-12 11:45 ` Martin Liška
2019-06-12 12:50 ` Richard Biener
2019-06-12 13:05 ` Martin Liška
2019-06-23 23:08 ` Ian Lance Taylor
2019-06-24 12:29 ` Richard Biener
2019-06-24 13:51 ` Martin Liška
2019-06-24 14:10 ` Richard Biener
2019-06-25 10:25 ` Martin Liška
2019-06-25 11:59 ` Martin Liška
2019-06-25 14:23 ` Richard Biener
2018-10-30 10:25 ` hash-table violation in cselib.c Martin Liška
2018-11-01 11:57 ` Martin Liška
2018-10-30 10:46 ` hash-table violation in gcc/fortran/trans-decl.c Martin Liška
2018-10-31 10:00 ` Trevor Saunders
2018-10-31 10:18 ` Martin Liška
2018-10-30 11:07 ` hash-table violation in gcc/cp/pt.c Martin Liška
2018-10-30 11:21 ` Martin Liška
2018-11-01 12:06 ` Martin Liška
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