Re: [Firebird-devel] Reference counters in API

[Alex P. <pes...@ma...>]

 On 03/29/11 18:58, Adriano dos Santos Fernandes wrote:
> On 29-03-2011 10:45, Alex Peshkoff wrote:
>>  We have too many problems in single thread. I try to divide it to
>> smaller parts.
>> The first one - here we at least all seem to talk about same thing:-) -
>> is to use reference counters or not.
>>
>> On 03/28/11 22:45, Adriano dos Santos Fernandes wrote:
>>> User should *not* request a detachment and then request actions on the
>>> objects. This *is* user application problem, no mater it being single or
>>> multi thread.
>> In that case our new API is regression compared with old ISC API with
>> handles. Pre FB3 an attempt to request actions on the objects after
>> detachment cause correct reply from client library - invalid handle.
>> Without reference count support we will get segfault in FB3. I treat
>> this as serious regression.
>>
> You're trying to make two different worlds to look similar.
>
> Take another look at it.
>
> Thread 1 detachs and makes it handle invalid.
>
> Thread 2 allocs 0xFFFFFFFF handles.
>
> Thread 3 is scheduled to run and use the old invalid, but now valid handle.
>
> Very pessimistic and "impossible" to happen, but shows that application
> doing this with handles are still incorrect.

As you understand yourself, this is not realistic example.
Cases when thread 3 is trying to work with old invalid handle and gets
appropriate error message is reality.
> You also didn't replied yet to me what will happen when you detach a
> parent without free children: leaks or will regret your refcounters?

Sorry, may be I've missed that question.
The answer is simple - objects will exist until refcounters > 0, but
will be marked in a way, making them return 'object is invalid' error
for any request.

> In anyway, it shows you're using an incorrect solution.
>

This words are absolutely unrelated with what you've asked before...

>> As one of users replied: Object-based interfaces should use the refcount.
> Against him is almost entire world who built API without refcount.

All the world is ambiguous here. See for example
http://api.openoffice.org/docs/common/ref/com/sun/star/uno/XInterface.html
BTW, all people who care about thread safety build object-oriented API
with reference counters.