FA-90575 / Garbage collector invariants / Member archive

Conservative scan: tag bits left on candidate addresses · case 05

Exact references never match an object start, so objects referenced from the stack are not pinned.

Member previewVariant 5 · 3 implementations · 7 checks per implementation

Case contract

Conservative scanning of machine words. A word whose low three bits are 011 is a tagged heap pointer to address word - 3; all other words are immediates. objs are [start, size, allocated] in any order. A candidate address pins the allocated object whose start equals it, or, when interior pointers are enabled, the allocated object whose [start, start+size) contains it; addresses in gaps, in free blocks or outside the heap pin nothing. Return the sorted starts of pinned objects.

Why this case matters

Conservative collectors must neither miss real references nor pin unrelated or free memory.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression: tagged start pointers only	`[]`	`[1344, 1376]`	Failed

MEMBER ARCHIVE

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This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

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