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

[Jeff Law <law@redhat.com>]

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 :-)

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.

> +
> +/* Verify that all existing elements in th hash table which are
s/th/the/


Jeff