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fix mark bit operation.

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To optimize the sweep phase, there is bit operation to set mark
bits for out-of-range bits in the last bit_t.
However, if there is no out-of-ragnge bits, it set all last bit_t
as mark bits and it braek the assumption (unmarked objects will
be swept).
GC_DEBUG=1 makes sizeof(RVALUE)=64 on my machine and this condition
happens.

It took me one Saturday to debug this.
This commit is contained in:
Koichi Sasada 2020-08-02 03:23:16 +09:00
parent d5bed28889
commit f7cf600c8b
1 changed files with 5 additions and 1 deletions
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6
gc.c
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@ -4247,7 +4247,11 @@ gc_page_sweep(rb_objspace_t *objspace, rb_heap_t *heap, struct heap_page *sweep_
/* create guard : fill 1 out-of-range */
bits[BITMAP_INDEX(p)] |= BITMAP_BIT(p)-1;
bits[BITMAP_INDEX(p) + sweep_page->total_slots / BITS_BITLENGTH] |= ~(((bits_t)1 << ((NUM_IN_PAGE(p) + sweep_page->total_slots) % BITS_BITLENGTH)) - 1);
int out_of_range_bits = (NUM_IN_PAGE(p) + sweep_page->total_slots) % BITS_BITLENGTH;
if (out_of_range_bits != 0) { // sizeof(RVALUE) == 64
bits[BITMAP_INDEX(p) + sweep_page->total_slots / BITS_BITLENGTH] |= ~(((bits_t)1 << out_of_range_bits) - 1);
}
for (i=0; i < HEAP_PAGE_BITMAP_LIMIT; i++) {
bitset = ~bits[i];