On Sun, Nov 18, 2012 at 11:25:55AM -0500, Diego Novillo wrote: > I agree with the analysis of Uday and Basile. [...] > > However, let's discuss this topic in some other thread, please. I'd > like to take this thread back to the original topic: what do we do > with GC and PCH?
I really think that GCC need some form of garbage collector. If it is Ggc+gengtype (to be improved), or Boehm GC, or even some other GC (for instance both http://starynkevitch.net/Basile/qishintro.html and http://gcc.gnu.org/viewcvs/branches/melt-branch/gcc/melt-runtime.c are or contain precise copying collectors that I wrote, and with some effort that could be made nicely compatible with C++). But my feeling is that a lot of people don't want GCC to have any kind of garbage collector and dream of having only manual allocation & de-allocation (I Basile personally think that it is not realistic and not desirable, because it will make future contributions to GCC much more costly to develop, and I probably would myself lose interest in GCC when garbage collection will be removed). Regarding PCH [pre-compiled header], I think that it is related to PPH [pre-processed headers] I don't understand yet if PPH is abandoned, or just post-poned. I was believing it was a very mature experimental branch. A very related question, now that we have switched to C++, is: do we accept the idea of having a common ancestor class (e.g. a GccObject root class for GCC, like GObject is for GTK and QObject is for Qt) with virtual methods (i.e. do we accept a vtable) for essential GCC datatypes like edge, gimple, basic_block and tree-s. My understanding is that many people firmly reject such an idea (probably because it might perhaps make gimple one word fatter). But I would easily imagine that having a single top GccObject root class, with several virtual abstract methods inside, could considerably help in implementing new garbage collection scheme and a lot of utility functionality (e.g. for dump perhaps LTO & perhaps PCH we would just have some virtual methods in GccObject for them). I also don't understand if PCH is really important; I feel that very few people are using it (in particular, because it practically requires a single header file for all of the application). In other words, could we give up PCH (probably not, but I don't understand why), e.g. give up PCH for GCC 5.0 (and aim to have PPH for GCC 5.1)? My feeling is that the question of having a garbage collector inside GCC is not the same as the question of keeping gengtype+ggc in its present form (or in an improved form). At last, I don't understand if experimenting with e.g. a single GccObject root class is easily feasible (is it a matter of just adding some inheritance in a few *.h files, or is it much worse than that). Now, I do admit that I don't have a clear overall picture about GCC, and that all global reviewers have a much better whole picture of GCC than I do. BTW, perhaps what might be missing is a good analysis & detailed metrics of the existing GCC source base. Perhaps some plugin or extension of GCC could help to make it. (I Basile would be very happy to work on a MELT extension to access and measure and navigate inside the entire GCC compiler, but this is a quite big project, and I don't know how could I be funded to work on this). Regards. -- Basile STARYNKEVITCH http://starynkevitch.net/Basile/ email: basile<at>starynkevitch<dot>net mobile: +33 6 8501 2359 8, rue de la Faiencerie, 92340 Bourg La Reine, France *** opinions {are only mines, sont seulement les miennes} ***
