Laurynas Biveinis wrote: > Daniel, first of all, how would you prefer to communicate on general > GCC issues? Is it OK to send e-mail to you and to gcc mailing list, or > should I send such mails to gcc mailing list only?
Copying me is fine for me. > > Some of the GCC roots live on the heap memory, e.g. ident_table. These > are not found by Boehm's GC by default. I've started fixing such > places by registering these additional roots. But it got me thinking: > how do the old GCC garbage collectors know about those roots? There is a root list, generated by gengtype from parsing the files looking for those GTY markers. I do not > see any root registration calls, but maybe I do not know where to > look. So, if you look at ggc_mark_roots, you can see the walker that is walking the root table. If you look in your *build* directory, and grep for ggc_root_tab, you will see where the roots are. Again, these are all auto-generated from gengtype. You can simply register them with boehm once gcc starts, because the root set never changes. One thing i should mention to you at this point, if you haven't discovered yet, is that it is *not safe* to do collections in between ggc_collect calls right now (IE when ggc_alloc is called). At least, not without walking *everything* looking around for possible roots, because places don't expect ggc_alloc'd memory without a "real" root (IE registered in the root table) memory to disappear until the next ggc_collect call. Thus, it is common practice for intra-pass garbage is just allocated without a root using ggc_alloc, and expected to disappear by virtue of having no registered root the next time ggc_collect is called.
