GC API: Difference between revisions

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GC API (view source)

Revision as of 14:23, 8 April 2008

1,746 bytes removed ,  8 April 2008
→‎The Memory API: move as promised
(→‎The Memory API: move as promised)
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'''Open issue:''' Whether we can discard the SpiderMonkey 1.8 tracing API.
'''Open issue:''' Whether we can discard the SpiderMonkey 1.8 tracing API.


= The Memory API =
= The GC Internals API =


This is a description of the private API that the allocator needs to provide to the GC engine which runs atop it.  (The allocator also provides all the Allocation and Layout APIs, which are user-visible.)
Mozilla's implementation of the GC API will consist of an allocator and a garbage collector.  The allocator will implement many of the above features ...plus a mostly-private API for the use of the garbage collector.


/* APIs for marking */
This mostly-private API is being designed at [[GC Internals API]].
/* Begin the process of mark/sweep: after this call, gc_is_marked should
    return GC_UNMARKED for all allocations */
void gc_begin_mark(gcheap *heap);
/* @param object must be the outermost pointer to the allocation */
void gc_mark_object(gcheap *heap, void *object);
/* Get the "next" object which has been marked but not yet processed.
    The GC engine needs to know about the object layout, but I don't know
    the best way to expose this (or whether the allocator ought to do that?) */
void * gc_get_next_unprocessed(gcheap *heap, some_kind_of_layout_object);
typedef enum gcmarkstate {
  GC_NOT_GCOBJECT, /* this pointer is not a gc allocation */
  GC_UNMARKED,
  GC_MARKED,    /* gc_mark_object, but not yet gc_get_next_unprocessed */
  GC_PROCESSED  /* processed by gc_get_next_unprocessed */
} gcmarkstate;
/* @param object must be an exterior pointer to an object in this heap */
gcmarkstate gc_get_markstate(gcheap *heap, void *object);
/* @param object inout - in is a conservative pointer
                  if the function returns something other than GC_NOT_GCOBJECT,
                  it will be set to the "outer" pointer */
gcmarkstate gc_conservative_beginning(gcheap *heap, void **object);
/* Inform the allocator that we're done marking. The allocator will sweep
    all unmarked objects, firing finalizers where appropriate. */
gc_end_mark(gcheap *heap);
 
Things to be specified:
 
* Synchronization
* RCObjects - other than write barriers and a flag bit, I don't think the allocator itself needs to know anything about RCObjects
 
jasone asks:
<ul>
<li> Are "outermost pointer" and ("exterior pointer" or "outer pointer") distinct concepts? bsmedberg says no, they are synonyms. We should really use a typedef to make it explicitly clear.</li>
</ul>
Jorend
638

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