[Interest] Problem creating a dll that loads static Qt libraries (in mingw) -> final chapter

erick oliveira da silva eosilva2000 at ig.com.br
Sat Jan 21 23:01:40 CET 2012


Thanks, Till.

Muito Obrigado pela resposta, Till.

P.S.: rolou um pouco de inveja de minha parte agora. Só poderei visitar o
Brasil no natal. :-(

Best Regards,
Erick

2012/1/21 Till Oliver Knoll <till.oliver.knoll at gmail.com>

>
>
> Am Freitag, 20. Januar 2012 schrieb Andreas Pakulat <apaku at gmx.de>:
>
> > On 20.01.12 07:23:43, Till Oliver Knoll wrote:
> >>
> >>
> >> Am 20.01.2012 um 07:14 schrieb erick oliveira da silva <
> eosilva2000 at ig.com.br>:
> >>
> >> > Hi Till,
> >> >
> >> > ...
> >> > CONFIG += qt dll release
> >>
> >> Oops, not sure, but I think that's the bugger: can't remember right now
> the exact meaning of 'dll',
>  > Maybe you should do so before posting comments that you're not quite
> > sure of ;)
>
> Eeeh! Yes, sorry, it just occured to my mind an hour later or so that what
> I wrote is bogus info! So please ignore that and "delete it from the
> Internet" ;)
>
> Yes, off course 'dll' refers to how /your/ code is to be linked (another
> option being 'plugin'), that is, a DLL (shared library) is to be produced.
>
> (But I have a good excuse: I'm on holidays in lovely Brasil, and am typing
> this on some tiny mobile screen where it is absolutely no fun to do docu
> research - you know, the heat, Caipirinha and such ;))
>
>
>
> > That being said, it might still be the cause of the problems, since not
> > all linkers might support linking a static library into a shared one
> > ...
>
> > And even those that do will only take the symbols that the shared
> > library uses, so if you then link an app against the shared lib and
> > expect it to automatically get all Qt symbols from the shared lib that
> > won't work either.
>
> I think that's the answer! Off course, it must be: When you link against a
> static library only those symbols which are actually used are linked into
> your binary. And depending on how good the linker is able to optimise (or
> how the compiler creates dependencies maybe as well) you get a few symbols
> more or less linked into your binary - but for sure not the entire library!
>
> That would explain why it might work with one linker A, whereas it might
> not work with another linker B.
>
>
> On the other hand: the example code did not expose (export) any Qt API, so
> as long as such a dynamic library would use Qt only /internally/ (with no
> references to any Qt classes in its headers), then in theory that should
> work to link such a dynamic lib with a static Qt one.
>
> But Andreas might be right: some compilers/linkers might simply not
> support that (correctly).
>
>
> Cheers, Oliver
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