[poppler] Object management helper class

[Carlos Garcia Campos]

Albert Astals Cid <aacid at kde.org> writes:

> El dimarts, 31 de maig de 2016, a les 11:46:38 CEST, Carlos Garcia Campos va 
> escriure:
>> Albert Astals Cid <aacid at kde.org> writes:
>> > El dilluns, 30 de maig de 2016, a les 15:43:19 CEST, Carlos Garcia Campos
>> > va> 
>> > escriure:
>> >> Albert Astals Cid <aacid at kde.org> writes:
>> >> > Hi guys, related to the previous email about std::unique_ptr I think we
>> >> > would greatly benefit of a class that makes Object management easier.
>> >> > 
>> >> > Again if you go and check https://bugs.freedesktop.org/attachment.cgi?
>> >> > id=124163 we're missing lots of free() and it's hard to prove we won't
>> >> > miss
>> >> > more.
>> >> > 
>> >> > My suggestion is adding a class called UniqueObject (better name
>> >> > welcome)
>> >> > 
>> >> > which will:
>> >> >  * Call free on itself when it goes out of scope
>> >> >  
>> >> > 	So we don't need to add .free() in every other if-chek-error-return
>> >> > 	
>> >> >  * Call free on itself when you write on it
>> >> >  
>> >> > 	So we can do
>> >> > 	
>> >> > 	dict->lookup("Decode", &obj1);
>> >> > 	
>> >> >     if (obj1.isNull()) {
>> >> >     
>> >> >       dict->lookup("D", &obj1);
>> >> >     
>> >> >     }
>> >> > 
>> >> > instead of
>> >> > 
>> >> > 	dict->lookup("Decode", &obj1);
>> >> > 	
>> >> >     if (obj1.isNull()) {
>> >> >     
>> >> >       obj1.free();
>> >> >       dict->lookup("D", &obj1);
>> >> >     
>> >> >     }
>> >> > 
>> >> > What do you think?
>> >> 
>> >> Why do we need a new class? Wouldn't it be enough to call free in the
>> >> Object destructor and init* methods?
>> > 
>> > Not really enough, we need to fix shallowCopy and the operator= that is
>> > used randomly in the code, and also the whole rest of the code.
>> > 
>> > I agree this may be the best, to not have two "Object" systems at the same
>> > time, but it's also a very big change that needs removing of all the
>> > free()
>> > calls (well not really since gree of a free object does nothing but still
>> > would look weird).
>> > 
>> > If we wanted to do this i guess we would do:
>> >  * add destructor with free
>> >  * call free in the initObj define
>> >  * Rename shallowCopy to be like "takeObject" that would take the internal
>> > 
>> > data and set the other objcet to none
>> 
>> Or better remove shallowCopy and use std::move()
>> 
>> >  * Make operator= private so people are forced to use takeObject
>> 
>> Or make the object non-copyable by defining the copy constructor and
>> operator= as =delete.
>> 
>> >  * Make free() private so we can easily remove all its uses
>> > 
>> > And maybe that would be all?
>> 
>> It seems so
>> 
>> > Sounds doable-ish?
>> 
>> Definitely.
>
> I did work a bit on this (your C++11 suggestions) and it's doable, it's a bit 
> tricky in Stream where all the Stream seem to share the same Dict by virtue of 
> assigning it around, but i think i'd make it work eventually.

We could even remove copy() and make = always copy. Dicts are refcounted
anyway, so copies should be cheap in any case. But I haven't looked at it in
detail yet, just proposed ideas without actually trying anything :-P

> There's a problem though, doing that we expose C++11 in the "internal" API, 
> and I'm not sure the consumers of that internal API will be happy.
>
> In theory we've said multiple times we don't care, that people should be using 
> one of the frontends, but that just doesn't happen, and if we break the API in 
> a way say libreoffice or latex can't use us anymore we basically make 
> upgrading poppler almost impossible for distros.
>
> So i will now try to do it the way I suggested (that is with some more manual 
> C++), I suggest we start by limiting C++11 to the .cc files for now.
>
> Am I making sense?

I would ask LO and pdflatex devs first, maybe it's not a problem at all
for them.

> Cheers,
>   Albert
>
>> 
>> > Cheers,
>> > 
>> >   Albert
>> >   
>> >> > Cheers,
>> >> > 
>> >> >   Albert
>> >> > 
>> >> > _______________________________________________
>> >> > poppler mailing list
>> >> > poppler at lists.freedesktop.org
>> >> > https://lists.freedesktop.org/mailman/listinfo/poppler
>
>

-- 
Carlos Garcia Campos
PGP key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x523E6462
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