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

[Jeff Law <law at redhat dot com>]

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 :-)


Jeff