On 06/17/2015 01:29 PM, Richard Biener wrote:
> On Wed, Jun 17, 2015 at 1:22 PM, Jakub Jelinek <ja...@redhat.com> wrote:
>> On Wed, Jun 17, 2015 at 11:13:58AM +0200, Martin Jambor wrote:
>>>>>> Do you mean Richard following changes:
>>>>>>
>>>>>> alloc-pool.h (allocate):
>>>>>> ...
>>>>>> + /* Placement new contructor. */
>>>>>> + inline void *operator new (size_t, elt_loc_list *&ptr)
>>>>>> + {
>>>>>> + return ptr;
>>>>>> + }
>>>>>
>>>>> That should be there with including <new>
>>>>>
>>>>>> and e.g. cselib.h:
>>>>>>
>>>>>> struct cselib_val
>>>>>> {
>>>>>> /* Pool allocation new operator. */
>>>>>> inline void *operator new (size_t)
>>>>>> {
>>>>>> return pool.allocate ();
>>>>>> }
>>>>>>
>>>>>> /* Placement new contructor. */
>>>>>> inline void *operator new (size_t, char *&ptr)
>>>>>> {
>>>>>> return ptr;
>>>>>> }
>>>>>
>>>>> Yes, though I wonder whether cselib_val should really have undefined
>>>>> contents after
>>>>> allocating it? (or does the pool allocator zero the memory?)
>>
>> IMHO if you want to put placement new into allocate, then you probably need
>> two different methods, one that will return you just void * to the
>> allocated memory chunk that you should use
>> inline void *operator new (size_t) { return pool.allocate (); } on,
>> and another method that will use that and additionally invoke a placement
>> new on it and return you the constructed pointer, which you'd use elsewhere.
>> Otherwise you'd construct the object twice...
>
> Note that in the case of cselib_val a
>
> new cselib_val;
>
> will already invoke the constructor. I think it's just too much
> (partly) C++-ification here.
> Either all alloc-pool users have to work that way or none.
>
> Richard.
>
>> Jakub
Hello.
You are right that we should call ::new just for classes that have
m_ignore_type_size == false.
I've come up with following patch, that I tested slightly:
diff --git a/gcc/alloc-pool.h b/gcc/alloc-pool.h
index 1785df5..7da5f7a 100644
--- a/gcc/alloc-pool.h
+++ b/gcc/alloc-pool.h
@@ -412,8 +412,16 @@ pool_allocator<T>::allocate ()
#endif
VALGRIND_DISCARD (VALGRIND_MAKE_MEM_UNDEFINED (header, size));
+ T *ptr = (T *)header;
+
/* Call default constructor. */
- return (T *)(header);
+ if (!m_ignore_type_size)
+ {
+ memset (header + sizeof (T), 0, m_extra_size);
+ return ::new (ptr) T;
+ }
+ else
+ return ptr;
}
/* Puts PTR back on POOL's free list. */
Would it be suitable?
Martin
