On Fri, Apr 22, 2016 at 11:37 PM, Mikhail Maltsev <malts...@gmail.com> wrote:
> On 04/20/2016 05:12 PM, Richard Biener wrote:
>> You have
>>
>> +static tree
>> +handle_free_attribute (tree *node, tree name, tree /*args*/, int /*flags*/,
>> + bool *no_add_attrs)
>> +{
>> + tree decl = *node;
>> + if (TREE_CODE (decl) == FUNCTION_DECL
>> + && type_num_arguments (TREE_TYPE (decl)) != 0
>> + && POINTER_TYPE_P (TREE_VALUE (TYPE_ARG_TYPES (TREE_TYPE (decl)))))
>> + DECL_ALLOC_FN_KIND (decl) = ALLOC_FN_FREE;
>> + else
>> + {
>> + warning_at (DECL_SOURCE_LOCATION (decl), OPT_Wattributes,
>> + "%qE attribute ignored", name);
>> + *no_add_attrs = true;
>> + }
>>
>> so one can happily apply the attribute to
>>
>> void foo (void *, void *);
>>
>> but then
>>
>> @@ -2117,6 +2127,13 @@ call_may_clobber_ref_p_1 (gcall *call, ao_ref *ref)
>> /* Fallthru to general call handling. */;
>> }
>>
>> + if (callee != NULL_TREE
>> + && (flags_from_decl_or_type (callee) & ECF_FREE) != 0)
>> + {
>> + tree ptr = gimple_call_arg (call, 0);
>> + return ptr_deref_may_alias_ref_p_1 (ptr, ref);
>> + }
>>
>> will ignore the 2nd argument. I think it's better to ignore the attribute
>> if type_num_arguments () != 1.
>
> Actually, the C++ standard ([basic.stc.dynamic]/2) defines the following 4
> deallocation functions implicitly:
>
> void operator delete(void*);
> void operator delete[](void*);
> void operator delete(void*, std::size_t) noexcept;
> void operator delete[](void*, std::size_t) noexcept;
>
> And the standard library also has:
>
> void operator delete(void*, const std::nothrow_t&);
> void operator delete[](void*, const std::nothrow_t&);
> void operator delete(void*, std::size_t, const std::nothrow_t&);
> void operator delete[](void*, std::size_t, const std::nothrow_t&);
>
> IIUC, 'delete(void*, std::size_t)' is used by default in C++14
> (https://gcc.gnu.org/ml/gcc-patches/2014-12/msg01266.html). How should we
> handle
> this?
Hmm. I guess by adjusting the documentation of the attribute to
explicitely mention
the behavior on the rest of the argument pointed-to memory (the
function is assumed
to neither write nor read from that memory). Also explicitely mention
that 'this' is
always the first argument if present.
Richard.
> --
> Regards,
> Mikhail Maltsev
