Hi Elijah,

Thank you for your reply.
In future, please also CC to this ML on committing to mono/libgc.
Unfortunately, i don't have time to check it on NaCl target.

PS. I don't see anything else in mono master relevant to GC and NaCl in 2011.
(for convenience, we have a branch "mono_libgc" which is a copy of mono/master - https://github.com/ivmai/bdwgc/tree/mono_libgc )

05 03 2012, 23:11 Elijah Taylor <elijahtaylor-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>:
> Hi Ivan,
>
> nacl_register_gc_hooks is defined in libnacl.a.  Unfortunately, that
> library is really only meaningful with our newlib toolchain.  Thanks for
> reminding me, I've filed a bug:
> http://code.google.com/p/nativeclient/issues/detail?id=2635
>
> You may want to consider taking a couple more changes to that file (and
> other parts of libgc that we changed) in order to get something that will
> build and run with our glibc toolchain.  From September through January, a
> lot of changes went into Mono to make things work cleanly with our glibc,
> and a decent amount was getting libgc working in the different environment.
>  In fact, I've pretty much dropped support for using this with our newlib
> version.
>
> -Elijah
>
> On Mon, Mar 5, 2012 at 7:01 AM, Ivan Maidanski <ivmai-JGs/UdohzUI@public.gmane.org> wrote:
>
> > Hi Elijah,
> >
> > I've cherry-picked your latest commit regarding NaCl from mono/libgc to
> > BDWGC master branch (with minor modifications):
> >
> > https://github.com/ivmai/bdwgc/commit/14f2760d584c18fc8a1f305f5ed0a6d13ff5918a
> >
> > I wonder where is nacl_register_gc_hooks defined?
> >
> > Thanks.
> >
> > 18 04 2011, 22:31 Elijah Taylor <elijahtaylor-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>:
> > > Hi Ivan,
> > >
> > > If I can add a couple of functions to our pthread implementation
> > > (pthread_getattr_np and pthread_getattr_getstack) then we should be able
> > to
> > > just use the GC_LINUX_THREADS version and take off the "!defined(NACL)".
> > >  I'll let you know of my progress when I have something to report.
> > >
> > > -Elijah
> > >
> > > On Sat, Apr 16, 2011 at 1:48 AM, Ivan Maidanski <ivmai-JGs/UdohzUI@public.gmane.org> wrote:
> > >
> > > > Hi Elijah,
> > > >
> > > > Could you also provide GC_get_stack_base() implementation for NaCl?
> > (just
> > > > for the completeness of the port)
> > > >
> > > > Thanks.
> > > >
> > > > Sat, 22 Jan 2011 16:23:32 -0800 Elijah Taylor <elijahtaylor-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org
> > >:
> > > >
> > > > Hi Ivan,
> > > >
> > > > Sorry I haven't gotten back to you yet, I've been busy with other
> > things
> > > > this last week.  I'm planning on addressing the feedback you've given
> > me so
> > > > far in the next week, and I can send you a more detailed response to
> > your
> > > > other questions at that time.  Thanks for the help so far.
> > > >
> > > > -Elijah
> > > >
> > > >
> > > > On Sat, Jan 22, 2011 at 9:09 AM, Ivan Maidanski <ivmai-JGs/UdohzUI@public.gmane.org<
> > http://sentmsg?compose&To=ivmai-JGs/UdohzUI@public.gmane.org>
> > > > > wrote:
> > > >
> > > >> Hi Elijah,
> > > >>
> > > >> Any progress or comments?
> > > >>
> > > >> Sat, 15 Jan 2011 15:36:47 +0300 Ivan Maidanski <ivmai-JGs/UdohzUI@public.gmane.org<
> > http://sentmsg?compose&To=ivmai-JGs/UdohzUI@public.gmane.org>
> > > >> >:
> > > >>
> > > >> > Hello Elijah,
> > > >> >
> > > >> > Fri, 14 Jan 2011 15:36:34 -0800 письмо от Elijah Taylor <
> > > >> > elijahtaylor-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org<
> > http://sentmsg?compose&To=elijahtaylor-hpIqsD4AKldhl2p70BpVqQ@public.gmane.orgm>(sentmsg?compose&To=
> > > >> elijahtaylor-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org<
> > http://sentmsg?compose&To=elijahtaylor-hpIqsD4AKldhl2p70BpVqQ@public.gmane.orgm>)
> > > >> >:
> > > >> >
> > > >> > > Hi Ivan,
> > > >> > >
> > > >> > > Thanks for taking a look, I'm pleasantly surprised by the level of
> > > >> detail
> > > >> > > here.  Specific replies inline:
> > > >> > >
> > > >> > >
> > > >> > > On Fri, Jan 14, 2011 at 2:50 PM, Ivan Maidanski < ivmai-JGs/UdohzUI@public.gmane.org<
> > http://sentmsg?compose&To=ivmai-JGs/UdohzUI@public.gmane.org>
> > > >> > (sentmsg?compose&To=ivmai-JGs/UdohzUI@public.gmane.org<
> > http://sentmsg?compose&To=ivmai-JGs/UdohzUI@public.gmane.org>)
> > > >> > wrote:
> > > >> > >
> > > >> > > - the patch in  naclports repository contains a typo in a macro
> > > >> definition
> > > >> > > > (MAC_TYPE -> MACH_TYPE);
> > > >> > >
> > > >> > > Oops, will fix.
> > > >> >
> > > >> > Why not to leave MACH_TYPE as-is (e.g. "I386", etc.)? NaCl is a
> > kind of
> > > >> OS not
> > > >> > a kind of machine hardware.
> > > >> > Is eg. I386 defined for x86?
> > > >> >
> > > >> > Also, please add a mapping comment in gcconfig.h (around "Feel free
> > to
> > > >> add
> > > >> > more clauses here").
> > > >> >
> > > >> > >
> > > >> > > > - the patch in  naclports repository looks more suitable for gc
> > v72
> > > >> than
> > > >> > > > that for mono/libgc;
> > > >> > > >
> > > >> > >
> > > >> > > This patch is meant to be applied to vanilla gc6.8.  The
> > mono/libgc
> > > >> port is
> > > >> > > already patched directly into mono's code repository.
> > > >> >
> > > >> > Yes, I only meant the vanilla gc6.8 patch contains some more code
> > (eg,
> > > >> for
> > > >> > PARALLEL_MARK) not present in mono/libgc.
> > > >> >
> > > >> > > > - gc_pthread_redirects.h (which is a public one) should not test
> > > >> NACL
> > > >> > macro
> > > >> > > > (or, at least, while less desirable, it should be prefixed with
> > > >> GC_);
> > > >> > > >
> > > >> > >
> > > >> > > Ok, makes sense, I think I didn't realize this was a public
> > header.
> > > >>  Though
> > > >> > > that explains why I had to add a test for __native_client__
> >  (which is
> > > >> > > defined in our toolchain).  I'll fix this.
> > > >> > >
> > > >> > > > - it's not clear why you need to explicitly undef STACK_GRAN,
> > > >> > USE_M[UN]MAP,
> > > >> > > > etc. in gcconfig.h;
> > > >> > > >
> > > >> > >
> > > >> > > I'll do some investigation, but IIRC these were needed at one
> > point
> > > >> for me.
> > > >> > > There's a good chance these may be unnecessary and vestigial.
> > > >> >
> > > >> > There should none "undef" (no other target undefining them).
> > > >> >
> > > >> > If mmap is supported by NaCl then it might be possible to support
> > > >> > USE_M[UN]MAP.
> > > >> >
> > > >> > > > - is MPROTECT_VDB supported or not?;
> > > >> > >
> > > >> > > Is MPROTECT_VDB equivalent to catching protection violations in
> > the GC
> > > >> code?
> > > >> > > If so, then no, we don't support anything like that right now.
> > > >>  Protection
> > > >> > > violation in NaCl == instant death.
> > > >> >
> > > >> > Ok, so MPROTECT_VDB (i.e., incremental/generation collection) is not
> > > >> > supported.
> > > >> >
> > > >> > > > - if you you want to port gc72 please use the recent CVS
> > snapshot
> > > >> (it
> > > >> > would
> > > >> > > > be easier to me to review and commit it);
> > > >> > >
> > > >> > > I've been grabbing source from
> > > >> > >  http://www.hpl.hp.com/personal/Hans_Boehm/gc/gc_source/
> > > >> > (http://www.hpl.hp.com/personal/Hans_Boehm/gc/gc_source/)  ... can
> > you
> > > >> point
> > > >> > me
> > > >> > > to where I should be getting the latest?  It's not immediately
> > obvious
> > > >> to
> > > >> > > me.
> > > >> >
> > > >> > http://bdwgc.cvs.sourceforge.net/viewvc/bdwgc/bdwgc/
> > > >> > (For convenience, I have a recent snapshot as a tarball which I use
> > for
> > > >> my
> > > >> > project -
> > > >> >
> > http://www.ivmaisoft.com/_mirror/hpl/bdwgc-7_2alpha5-20110107.tar.bz2)
> > > >> >
> > > >> > > - not sure that HEURISTIC1 really works reliably there (in short,
> > > >> HEURISTIC1
> > > >> > > > means you treat stack pointer at GC_init call as stack bottom -
> > is
> > > >> it
> > > >> > > > guaranteed that GC_init call is always done at higher stack
> > > >> addresses than
> > > >> > > > any other GC call);
> > > >> > > >
> > > >> > >
> > > >> > > HEURISTIC2 will definitely not work for us as it wants to use a
> > > >> segfault to
> > > >> > > detect running over the stack.  I've set STACK_GRAN to 64K, so as
> > long
> > > >> as
> > > >> > > the stack doesn't grow beyond that size before GC_init, we should
> > be
> > > >> ok,as
> > > >> > > right?  The stack for the main thread right now in NaCl lives at a
> > > >> fixed
> > > >> > > address usually, but that isn't guaranteed for all future time,
> > so I'd
> > > >> > > prefer not to hard code magic numbers here.
> > > >> >
> > > >> > No, HEURISTIC2 won't work without signals, but there are other
> > > >> alternatives:
> > > >> > - if threads-support is on then is it possible to use
> > > >> > USE_GET_STACKBASE_FOR_MAIN?;
> > > >> > - is it possible to LINUX_STACKBOTTOM (if we are on real Linux)?
> > > >> > - for NaCl on Cygwin, it might be possible to use
> > > >> GC_get_[main_]stack_base
> > > >> > based on __asm__ ("%fs:4").
> > > >> >
> > > >> > > > - is the GC port compilable (and working) on other (non-Linux)
> > > >> platforms
> > > >> > > > (eg., Cygwin);
> > > >> > > >
> > > >> > >
> > > >> > > Native Client is meant to be portable, so it should run on any
> > x86 or
> > > >> x86-64
> > > >> > > machine once it's built.  In terms of building, I haven't built
> > this
> > > >> gc port
> > > >> > > personally on Mac or Windows, but I just checked our build bot
> > logs
> > > >> and they
> > > >> > > seem to be building ok on Mac and in Cygwin.
> > > >> >
> > > >> > So, eg. DARWIN, GC_DARWIN_THREADS,  WIN32, CYGWIN, GC_WIN32_THREADS
> > > >> won't ever
> > > >> > be defined when building NaCl, right?
> > > >> > Is GC_LINUX_THREADS defined when building NaCl with multi-threaded
> > > >> support?
> > > >> >
> > > >> > I have very little knowledge of NaCl - could you briefly explain
> > what
> > > >> does
> > > >> > stand for NaCl portability - is it possible to call Win32 API if I'm
> > > >> compiling
> > > >> > on Cygwin or should I use the NaCl API (and, thus, the compiled
> > binary
> > > >> code
> > > >> > will run on any x86 target)?
> > > >> >
> > > >> > If NaCl is some kind of OS then LINUX, DARWIN, WIN32, etc shouldn't
> > be
> > > >> defined
> > > >> > (even if __linux__ defined) if NACL.
> > > >> > Same for GC_xxx_THREADS - I think GC_NACL_THREADS could be defined
> > > >> instead of
> > > >> > GC_LINUX_THREADS, etc.
> > > >> >
> > > >> > I also think that I386 and X86_64 should stay defined for
> > respectively
> > > >> the
> > > >> > corresponding CPU type (I guess it is already for NaCl but i haven't
> > > >> checked
> > > >> > yet)
> > > >> > I think there should be 2 ifdef NACL define OS_TYPE "NACL" ...
> > sections
> > > >> (one
> > > >> > for every supported CPU).
> > > >> >
> > > >> > > > - for non-static GC-internal symbols use GC_ prefix (eg. for
> > > >> > > > nacl_thread_parked);
> > > >> > > > - define SIG_SUSPEND to -1 (instead of 0) as it is returned by
> > > >> > > > GC_get_suspend_signal;
> > > >> > > > - GC functions called from NaCl it self (eg,
> > nacl_pre_syscall_hook)
> > > >> shoud
> > > >> > > > be tagged with some attribute (like public GC functions are)
> > both
> > > >> for code
> > > >> > > > readability and to prevent that symbols stripping when compiled
> > as a
> > > >> > shared
> > > >> > > > lib with -DGC_DLL);
> > > >> > > >
> > > >> > >
> > > >> > > I'll address these issues.  (note that NaCl currently doesn't
> > support
> > > >> shared
> > > >> > > libs yet so your dll example won't happen, but I agree that these
> > > >> should be
> > > >> > > treated like other public GC functions)
> > > >> >
> > > >> > Ok. But what is eg. nacl_pre_syscall_hook() - a callback from the
> > NaCl
> > > >> > subsystem? (I guess this should be treated as GC public API)
> > > >> >
> > > >> > Of course, use STATIC or static where possible (all STATIC symbols
> > start
> > > >> with
> > > >> > GC_, while static typically not).
> > > >> > More tips: use GC_INNER and GC_EXTERN for internal global
> > variables; use
> > > >> > GC_INNER for internal functions.
> > > >> >
> > > >> > > > - libatomic_ops does not use signals API (except for CAS
> > emulation
> > > >> which
> > > >> > is
> > > >> > > > not used for x86/x64).
> > > >> > >
> > > >> > > I think I saw sigprocmask and related functions and assumed the
> > worst,
> > > >> but I
> > > >> > > see now that's windows code.  Looking at the x86 variants it looks
> > > >> like a
> > > >> > > NaCl port of libatomic_ops is probably not going to be too bad.
> >  I'll
> > > >> look
> > > >> > > into this eventually.
> > > >> >
> > > >> > Most probably, it work w/o any porting afforts but it would be good
> > to
> > > >> port
> > > >> > atomic_ops.c (similar to what I did for Win32-pthreads targets - see
> > > >> > AO_USE_WIN32_PTHREADS, I guess you should add AO_USE_NACL macro
> > testing
> > > >> in
> > > >> > that file (looks easy to add). I think it's worth doing first (and
> > > >> submit me a
> > > >> > separate patch for libatomics_op when done).
> > > >> >
> > > >> > What's about GC_HAVE_BUILTIN_BACKTRACE and GC_CAN_SAVE_CALL_STACKS?
> > At
> > > >> least,
> > > >> > gc.h should be consistent with the GC implementation (I mean eg. if
> > > >> > GC_HAVE_BUILTIN_BACKTRACE not supported then it shouldn't be
> > defined in
> > > >> gc.h
> > > >> > regardless of __linux__, _MSC_VER, etc. provided
> >  __native_client__).
> > > >> Same for
> > > >> > GC_ADD_CALLER, GC_RETURN_ADDR.
> > > >> >
> > > >> > Regards.
> > > >> >
> > > >> > > > PS. Let me not do the benefits analysis (probably someone else
> > can
> > > >> do
> > > >> > > > this).
> > > >> > > >
> > > >> > > Well, if the gc7.2 port is as easy as it's looking now, I think
> > it's
> > > >> > > probably worth doing it.  I would still love to hear anyone chime
> > in
> > > >> on the
> > > >> > > benefits of gc7.2 vs 6.8 though
> > > >> > >
> > > >> > > > Regards.
> > > >> > > >
> > > >> > > > Thu, 13 Jan 2011 10:21:03 -0800 Elijah Taylor <
> > > >> elijahtaylor-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org<
> > http://sentmsg?compose&To=elijahtaylor-hpIqsD4AKldhl2p70BpVqQ@public.gmane.orgm>
> > > >> > (sentmsg?compose&To=elijahtaylor-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org<
> > http://sentmsg?compose&To=elijahtaylor-hpIqsD4AKldhl2p70BpVqQ@public.gmane.orgm>)
> > > >> >:
> > > >> > > >
> > > >> > > > > Hi GC folks,
> > > >> > > >
> > > >> > > > > I saw a little chatter in the archives related to porting
> > libgc to
> > > >> > Native
> > > >> > > > Client, so I joined this list to share some details. I'm the
> > > >> engineer at
> > > >> > > > Google who ported of libgc to Native Client for Mono. I've also
> > > >> included a
> > > >> > > > patch for vanilla gc6.8 in our naclports repository:
> > > >> > > >  http://code.google.com/p/naclports/ (
> > > >> http://code.google.com/p/naclports/)
> > > >> > . This version will be available to
> > > >> > > > users that want to use libgc as part of their Native Client
> > > >> projects.
> > > >> > > >
> > > >> > > > > Before porting gc6.8 I had attempted to port one of the newer
> > > >> versions,
> > > >> > > > gc7.2alpha4, but ran into snags. The largest snag right now I
> > think
> > > >> is
> > > >> > that
> > > >> > > > gc 7+ includes libatomic_ops which will require some non-trivial
> > > >> effort in
> > > >> > > > order to work under Native Client. Most notably we don't support
> > > >> signals;
> > > >> > > > that was the biggest effort in porting libgc in the first place
> > for
> > > >> NaCl,
> > > >> > > > and I assume that will require the most work in porting
> > > >> libatomic_ops too.
> > > >> > > >
> > > >> > > > > Can someone give me the high level details of what kind of
> > things
> > > >> we
> > > >> > > > might be missing if we only support gc6.8 instead of the latest
> > > >> version?
> > > >> > > > Because of our thread stopping implementation, we may not even
> > > >> benefit
> > > >> > from
> > > >> > > > some of the newer features. I just wanted to get a sense of
> > what the
> > > >> > > > benefits are of getting a newer version available for users.
> > > >> > > >
> > > >> > > > > -Elijah
> > > >>
> > > >>
> > > >
> > > >
> > >
> > >
> >
>
>