[Qt-interest] Qt library in (non)Qt application

[Tumarov Alexander]

Marco Borm wrote:


> Also under Windows there is no real problem sharing objects between app
> and dlls if you do it the right way:
> 1. Components sharing objects on the head must use the same heap-manager
> Typically this means using the same crt in all components and use them
> as a dll/so.
> 2. If you share objects using a base class / interface pointer don't
> miss the virtual deconstructor if the receiver should delete the object.
Hm... this is the point - I am not sure if the same CRT will solve this
issue. Can you drop a link that can shed a light on this topic more deeply?
I remember that I have some hard time of exporting stl objects out from
dlls... virtual destructor did not solved that. May be the issue was a
different CRTs... but anyway - I wanna be sure on this topic. At this point
it bother me more then existance of QApplication since that can be defined
as requirement (on this later).
> 
> I think the bigger problem here is that you don't know if the app will
> construct a QApplication or not.

This is a second issue. Can QApplication be instantiated inside library?
Will dll's objects work correctly with QApplication installed in application
itself (like queued connections or event's handling)?


Thank you in advance.

p.s.: To be honest - the issues with right memory handling bothers me a lot.
The possibility of existance of several heap managers can become a real
headache if new/delete used across library boundaries (and if "recommended"
way is used  - what created in library should be deleted in library
itself). Virtual destructors will not solve this since the final
memory "free" will operate on heap manager that used in the execution unit
of "delete" call (app/dll). I beleive that what you say is that the
difference in the way I link CRT. If it is going to be static linkage - I
will have the problem. If dynamic on both the app and dll - all of them
will get the only one CRT with only 1 heap manager and then there will be
no problem. Am I right or wrong?
BTW - good question  - is there any issues like this on linux/mac os?
Additional issues may arize if QT uses static variables inside their
libraries (if something inlined  - application and dll can get different
copies of the same variable).