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
