[haiku-development] Re: object on the hype, using it as parameter and then use delete

  • From: Fredrik Modéen <fredrik@xxxxxxxxx>
  • To: haiku-development@xxxxxxxxxxxxx
  • Date: Fri, 12 Sep 2008 15:41:32 +0200 (CEST)

>
> On 2008-09-12 at 15:13:24 [+0200], Fredrik Modéen <fredrik@xxxxxxxxx>
> wrote:
>>
>> > On Fri, 12 Sep 2008 13:56:21 +0200 (CEST), Fredrik Modéen wrote
>> >> this are how it's setup to work, it's only part of it but it showas
>> what
>> >> i'm talkning about.
>> >>
>> >> ...
>> >>
>> >> void
>> >> IconView::_SetIcon(BBitmap* mini)
>> >> {
>> >>  BAppFileInfo info();
>> >>  if (mini != NULL || force)
>> >>   info.SetIconForType(fType.Type(), mini, B_MINI_ICON);
>> >> }
>> >
>> > In that case you would just track down what SetIconForType() does. If
>> it
>> > copies the bitmap, then you're fine. Otherwise this is probably a
>> false
>> > positive.
>> >
>> > It seems that you are not subscribed to the commits mailing list.
>> Please
>> > make
>> > sure you are subscribed, as we are sometimes replying to commits there
>> > like I
>> > did for your change in r27438:
>> Ah yes in deed I need to subscribe to that list (done now..)
>>
>> >
>> > https://lists.berlios.de/pipermail/haiku-commits/2008-September/016893.html
>> >
>> > You make the same assumption that new cannot fail in r27448 which I
>> find a
>> > bad
>> > idea. You could say that it is true that new cannot return NULL, since
>> it
>> > should actually throw an error and not return NULL. However this is
>> not a
>> > reason to strip the NULL checks, but to make new into
>> new(std::nothrow)
>> > which
>> > actually returns NULL on a failed allocation (which can always
>> happen). I
>> > thought we had the general consensus that we use new(std::nothrow) and
>> > always
>> > check the result, but I'm not sure how the other see it.
>>
>> So it would be better to try to make a new new when I found a null like
>> this
>>
>> if (_fDevice == NULL)
>>  _fDevice = new BList();
>>
>> if(_fDevice != NULL){
>>  continue..
>> }
>>
>> or some thing similar.
>
> Nope, what Michael is referring to is, that you should never use the new
> operator like this:
>
>       Foo* x = new Foo(...);
>       x->DoSomething();
>
> Because this operator version will throw an exception when the memory
> cannot
> be allocated. Instead use the nothrow version and check the result
> explicitly:
>
>       Foo* x = new(std::nothrow) Foo(...);
>       if (x == NULL)
>               return B_NO_MEMORY;
>
>       x->DoSomething();
If I only had read this a little earlier :)

could we some how hide the other (old) new or replace this with
new(std::nothrow) and state that in Haiku are new == new(std::nothrow) but
you cant see this and you don't need to think about this only use new as
we did before?

>
> CU, Ingo
>
>


-- 
MVH
Fredrik Modéen

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