On Fri, Jun 14, 2013 at 11:21:06PM -0400, David Malcolm wrote: > I'm hoping that gcc 4.9 can support multiple "parallel universes" of gcc > state within one process, to ultimately support gcc usage as a library, > where multiple client threads can each have their own gcc context (or > "universe"). > > One issue with the above is the garbage collector. > > I think there are two possible ways in which "universe instances" could > interact with the GC: > > (a) have the universe instances be GC-managed: all parallel universes > share the same heap, requiring a rewrite of the GC code to be > thread-safe, > > or > > (b) have the "universe instance"/context manage GC, so that the state of > GC is per-universe: each universe has its own GC heap, entirely > independent of each other universe's GC heap. You can't share GC > pointers between universes. > > I don't think (a) is feasible.
I agree, but what would be the purpose to run many threads of GCC in parallel which don't share anything? At the very least, I would expect predefined global trees to be common to all of them. I'm thinking at least of The global_trees array. And don't forget plugins, which can (and do, for MELT) run the Ggc collector, and use the PLUGIN_GGC_START, PLUGIN_GGC_MARKING, PLUGIN_GGC_END I do think that making (in the long term) GCC usable as a library (like LLVM is) is a worthwhile goal, but I don't think that aiming that future library to be multi-threadable (or thread-friendly) is very realistic. At least, we should make the two goals separate: first, make GCC a library, then (and later) make that library thread friendly. So I might not be very happy of your patch .... 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} ***
