> On 07 Sep 2016, at 14:56, Ben Coman <b...@openinworld.com> wrote: > > On Tue, Sep 6, 2016 at 8:08 PM, Esteban Lorenzano <esteba...@gmail.com > <mailto:esteba...@gmail.com>> wrote: >> Hi, >> >> sorry for arriving so late to this, but I was on holidays :) >> this is how autoRelease works: >> >> 1) #autoRelease of an object registers object for finalisation with a >> particular executor. Then behaviour is divided: >> >> 2.1.1) for ExternalAddresses, it just registers in regular way, who will >> call #finalize on GC >> 2.1.2) finalize will just call a free assuming ExternalAddress was allocated >> (which is a malloc) >> >> 2.2.1) for all FFIExternalReference, it will register for finalisation what >> #resourceData answers (normally, the handle of the object) >> 2.2.2) finalisation process will call the object >> class>>#finalizeResourceData: method, with the #resourceData result as >> parameter >> 2.2.3) each kind of external reference can decide how to free that data (by >> default is also just freeing). >> >> An example of this is how CairoFontFace works (or AthensCairoSurface). > > > At the bottom of FFIExternalResourceExecutor class comment I read... > "Note that in #finalizeResourceData: you cannot > access any other properties of your instance, > since it is already garbage collected." > > But in my experiments it seems okay to access instance variables in #finalize. > For example... > > CXString >> autoRelease > self class finalizationRegistry add: self > > CXString >> finalize > Transcript crShow: 'Finalizing CXString ' ; show: self private_flags. > self dispose. > Transcript show: ', done!'. > > CXString >>private_flags > "This method was automatically generated" > ^handle unsignedLongAt: 5 > > Libclang getClangVersion autoRelease. > Smalltalk garbageCollect. > "==> Finalizing CXString 1, done! " > > > Is this an unlucky coincidence? Or maybe something changed from NB > to UFFI? (There is a reference to NB there)
yes, is a coincidence. the idea of using #finalizeResourceData: is that you keep minimal information (in general, just the handle)… this way we ensure instances will be collected because we will not have circular references (preventing the weakregistry to work). In general, you can always implement as you did it, but I would prefer the #finalizeResourceData: approach, even for structures. The only reason it is not implemented is because I didn’t reach the necessity, then I just skipped it (not in purpose, it was not in my head :P), but now is a good moment to implement it… if you want it :) Esteban > I am wary of believing my results contrary to the comment. That old > engineering principle "When things work, it may be only reinforcing > your misconceptions." :) > > cheers -ben > >> In you case, you will have something like: >> >> FFIExternalObject subclass: #CXString >> >> CXString class>>#finalizeResourceData: version >> self ffiCall: #(void clang_disposeString(void *version)) >> >> notice that here I casted to void*… this is because actually resourceData >> answers a pointer, not the object. >> >> cheers, >> Esteban
