Re: [Gc] Creating stack-like memory containing GC roots

Shiro - thank you very much.  I’ll check that out.


> On Sep 23, 2015, at 5:13 PM, Shiro Kawai <[email protected]> wrote:
> 
> I once used bdwgc's "kind" mechanism for the similar purpose.  The "kind" is
> conceptually a custom allocator with your own mark procedure.  So, you allocate
> your stack by the new kind so that GC knows about it, but you make the attached
> marker scan only the active region of your stack.
> 
> I suppose the kind mechanism is more for generic purpose (e.g. "atomic" or "stubborn"
> allocators are realized by kinds), so using it for just custom stack region may be
> an overkill.  The source suggests that the kind isn't for casual use.   I'd like bgwgc
> experts here to suggest better advices.
> 
> If you're interested, check Gauche's vm.c. 
> Look at the code inside #ifdef USE_CUSTOM_STACK_MARKER.
> 
> https://github.com/shirok/Gauche/blob/master/src/vm.c <https://github.com/shirok/Gauche/blob/master/src/vm.c>
> 
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> On Wed, Sep 23, 2015 at 9:52 AM, Christian Schafmeister <[email protected] <mailto:[email protected]>> wrote:
> 
> I’ve written a Common Lisp compiler that uses LLVM as the backend and that interoperates with C++.
> 
> I’m using the Boehm garbage collector and I need to create a stack alongside the regular C++ stack that holds GC roots.
> 
> Is there any way using the Boehm garbage collector to identify a region of memory that will contain this stack and continuously update the top of the stack so that Boehm only examines the region that can contain pointers?
> 
> I need to push a frame containing GC roots onto the stack and then later pop the frame.  Ideally I would just need to provide Boehm a pointer that points to the end of the current frame and everything from that address up to and including the first frame would be scanned for roots.
> 
> I have seen the GC_add_roots function but that lets me define a region once.  I need some way to continuously update the end of the stack.
> Currently I’m using GC_malloc and GC_free to allocate and free frames - but I feel that for something like a stack this has more overhead than I need.
> I’ve tried doing this all on the main C++ stack - but I have to use non-standard features like __builtin_alloca or variable length arrays and they have caused me a lot of grief.
> 
> Best,
> 
> Christian Schafmeister
> Professor,
> Chemistry Department
> Temple University
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