Re: [PATCH][RFC] Sanitize equals and hash functions in hash-tables.

["Martin Liška" <mliska@suse.cz>]

On 6/7/19 11:43 PM, Jason Merrill wrote:
> On Fri, Jun 7, 2019 at 8:14 AM Martin Liška <mliska@suse.cz> wrote:
>>
>> On 6/7/19 2:09 PM, Richard Biener wrote:
>>> On Fri, Jun 7, 2019 at 2:03 PM Martin Liška <mliska@suse.cz> wrote:
>>>>
>>>> On 6/7/19 10:57 AM, Richard Biener wrote:
>>>>> On Mon, Jun 3, 2019 at 3:35 PM Martin Liška <mliska@suse.cz> wrote:
>>>>>>
>>>>>> On 6/1/19 12:06 AM, Jeff Law wrote:
>>>>>>> On 5/22/19 3:13 AM, Martin Liška wrote:
>>>>>>>> On 5/21/19 1:51 PM, Richard Biener wrote:
>>>>>>>>> On Tue, May 21, 2019 at 1:02 PM Martin Liška <mliska@suse.cz> wrote:
>>>>>>>>>>
>>>>>>>>>> On 5/21/19 11:38 AM, Richard Biener wrote:
>>>>>>>>>>> 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?
>>>>>>>>>>
>>>>>>>>>> I don't a have problem with that. Apparently this changes fixes
>>>>>>>>>> PR90450 and PR87847.
>>>>>>>>>>
>>>>>>>>>> Changes from previous version:
>>>>>>>>>> - verification happens only when an element is searched (not inserted)
>>>>>>>>>> - new argument 'sanitize_eq_and_hash' added for hash_table::hash_table
>>>>>>>>>> - new param has been introduced hash-table-verification-limit in order
>>>>>>>>>>   to limit number of elements that are compared within a table
>>>>>>>>>> - verification happens only with flag_checking >= 2
>>>>>>>>>>
>>>>>>>>>> I've been bootstrapping and testing the patch right now.
>>>>>>>>>
>>>>>>>>> Looks like I misremembered the original patch.  The issue isn't
>>>>>>>>> comparing random two elements in the table.
>>>>>>>>>
>>>>>>>>> That it fixes PR90450 is because LIM never calls find_slot_with_hash
>>>>>>>>> without INSERTing.
>>>>>>>>>
>>>>>>>>
>>>>>>>> There's updated version of the patch where I check all find operations
>>>>>>>> (both w/ and w/o insertion).
>>>>>>>>
>>>>>>>> Patch can bootstrap on x86_64-linux-gnu and survives regression tests
>>>>>>>> except for:
>>>>>>>>
>>>>>>>> $ ./xgcc -B. /home/marxin/Programming/gcc/gcc/testsuite/gcc.dg/torture/pr63941.c -O2 -c
>>>>>>>> hash table checking failed: equal operator returns true for a pair of values with a different hash value
>>>>>>>> during GIMPLE pass: lim
>>>>>>>> /home/marxin/Programming/gcc/gcc/testsuite/gcc.dg/torture/pr63941.c: In function ‘fn1’:
>>>>>>>> /home/marxin/Programming/gcc/gcc/testsuite/gcc.dg/torture/pr63941.c:6:1: internal compiler error: in hashtab_chk_error, at hash-table.h:1019
>>>>>>>>     6 | fn1 ()
>>>>>>>>       | ^~~
>>>>>>>> 0x6c5725 hashtab_chk_error
>>>>>>>>      /home/marxin/Programming/gcc/gcc/hash-table.h:1019
>>>>>>>> 0xe504ea hash_table<mem_ref_hasher, false, xcallocator>::verify(ao_ref* const&, unsigned int)
>>>>>>>>      /home/marxin/Programming/gcc/gcc/hash-table.h:1040
>>>>>>>> 0xe504ea hash_table<mem_ref_hasher, false, xcallocator>::find_slot_with_hash(ao_ref* const&, unsigned int, insert_option)
>>>>>>>>      /home/marxin/Programming/gcc/gcc/hash-table.h:960
>>>>>>>> 0xe504ea gather_mem_refs_stmt
>>>>>>>>      /home/marxin/Programming/gcc/gcc/tree-ssa-loop-im.c:1501
>>>>>>>> 0xe504ea analyze_memory_references
>>>>>>>>      /home/marxin/Programming/gcc/gcc/tree-ssa-loop-im.c:1625
>>>>>>>> 0xe504ea tree_ssa_lim
>>>>>>>>      /home/marxin/Programming/gcc/gcc/tree-ssa-loop-im.c:2646
>>>>>>>> 0xe504ea execute
>>>>>>>>      /home/marxin/Programming/gcc/gcc/tree-ssa-loop-im.c:2708
>>>>>>>>
>>>>>>>> Richi: it's after your recent patch.
>>>>>>>>
>>>>>>>> For some reason I don't see PR87847 issue any longer.
>>>>>>>>
>>>>>>>>
>>>>>>>> May I install the patch with disabled sanitization in tree-ssa-loop-im.c ?
>>>>>>> Don't we still need to deal with the naked fprintf when there's a
>>>>>>> failure.  ie, shouldn't we be raising it with a gcc_assert or somesuch?
>>>>>>
>>>>>> Good point, I've just adjusted that.
>>>>>>
>>>>>> Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
>>>>>>
>>>>>> Ready to be installed?
>>>>>
>>>>> Ugh, the cselib one is really bad.  But I don't hold my breath for anyone
>>>>> fixing it ...
>>>>
>>>> Yes :D It's been some time and there's no interest in the PR.
>>>>
>>>>>
>>>>> One question - there's unconditional
>>>>>
>>>>> +         if (m_sanitize_eq_and_hash)
>>>>> +           verify (comparable, hash);
>>>>>
>>>>> which will read a global variable and have (possibly not inline) call
>>>>> to verify on a common path even with checking disabled.  So I think
>>>>> we want to compile this checking feature out for !CHECKING_P
>>>>> or at least make the if __builtin_expect (..., 0), ::verify not
>>>>> inlined and marked pure () (thus, !CHECKING_P is simplest ;)).
>>>>
>>>> Fixed. May I install the patch? The cselib issue can be solved later..
>>>
>>> You missed the second occurance
>>>
>>> -  m_searches++;
>>> +  if (m_sanitize_eq_and_hash)
>>> +    verify (comparable, hash);
>>
>> Yep ;) I've just install the patch.
> 
> This is breaking my build:
> 
> /home/jason/gt/gcc/hash-map.h:123:71: error: no matching function for
> call to ‘hash_table<hash_map<mem_alloc_d\
> escription<mem_usage>::mem_location_hash, mem_usage*,
> simple_hashmap_traits<default_hash_traits<mem_alloc_desc\
> ription<mem_usage>::mem_location_hash>, mem_usage*> >::hash_entry,
> false, xcallocator>::hash_table(size_t&, bo\
> ol&, bool&, mem_alloc_origin, const char*&, int&, const char*&)’
>      : m_table (n, ggc, gather_mem_stats, HASH_MAP_ORIGIN PASS_MEM_STAT) {}
> 
> Looks like this needs to be updated to pass an argument to the new
> sanitize_eq_and_hash parameter.
> 
> Jason
> 

Hi.

Sorry for the breakage, I've just fixed that in r272104.

Martin