Cesarus85--mjolnir-vr/docs/object_matching_logs/circular_queue_obj.md

circular_queue.obj exact-match strategy ledger

Scope and required toolchain

• Translation unit: source/memory/circular_queue.c
• Target: January 2002 source/memory/circular_queue.obj
• Compiler: XDK 3911 CL 13.00.9254.1
• Flags: /O2 /Oy- /DDEBUG /Dxbox
• Strict gate: tools/coff_compare.py / section_infos_equal
• Detailed experiment transcript: research/circular_queue_obj/EXPERIMENTS.md

No inline assembly, volatile byte forcing, undefined behavior, object-byte patching, compiler-flag changes, or fuzzy-match credit was used.

Validated baseline

Seven of eight functions are strict exact:

Function	Target/base size	Relocs	Normalized SHA-256	Result
circular_queue_reset	16/16	0/0	43bd388fa461cee2...	exact
circular_queue_validate	112/112	6/6	f6a98f7f32feb7df...	exact
circular_queue_new	96/96	4/4	89dac4b56b758d67...	exact
circular_queue_delete	48/48	3/3	90fd5b668d0661b3...	exact
circular_queue_size	32/32	1/1	691530e94ba7f3f2...	exact
circular_queue_free_space	48/48	1/1	fa1cb9aa5c44d00d...	exact
circular_queue_queue_data	240/240	12/12	cfe1f5adce7a13f3...	exact
circular_queue_dequeue_data	256/240	12/12	target 2981341a22238a314c0f885d555149dc279257b6109242e674f38ccfb0ccd1f9; base 40adf3be1fa79c0b9aaf6b169e37da2e59aa4e306efef68a9573b7aa7ec8dede	nonexact

The strict code result is therefore 7/8 functions and 592/848 target padded code bytes. All five owned .rdata COMDATs are raw-byte exact: 46 + 39 + 65 + 52 + 49 = 251/251 bytes. The object owns no .data or .bss.

The residual begins at normalized offset +0x4; 222 normalized bytes differ. The first relocation has the correct _circular_queue_validate destination but is at target/base address 14/12. January keeps the queue in EDI, the input size in ESI, initializes BL to false, later reuses EBX for read_offset, and returns BL only on failure. Current VC7 instead keeps the queue in EBX, read_offset in EDI, and folds false directly into AL.

January and cross-build provenance

• The October 2001 XBE function at VA 0x00118fb0 has the same machine topology instruction-for-instruction, including xor bl,bl, the EBX=read_offset lifetime reuse, and separate success/failure tails.
• January's PDB exposes the public symbol but no local-variable or line records for this function.
• HCEA exposes only the later simple_circular_queue_* family and is not a source donor for this implementation.
• A campaign-wide target scan found no second strict donor combining early byte-zero lifetime materialization with reuse of that register as a later long local and a final same-byte failure return.
• The two locally available authentic VC7 compilers, 13.00.9254.1 and 13.00.9210, emit the same baseline hash from unchanged source.

Accepted production source

The production source remains the safe semantic reconstruction with one result local, one success block, an optional read_offset writeback, and a single final return. It preserves all seven exact sibling functions and every owned data section. No experimental source shape was retained because none strictly improved the complete translation unit.

Experiment matrix

Every row was built with the required XDK compiler and flags. Unless stated otherwise, all seven exact siblings and all five .rdata sections remained exact. Hashes ending in ... are historical prefixes: the earlier session did not preserve the full digest, and the experiment was not rerun merely to lengthen a digest.

ID	Exact source delta	Base size/relocs/hash	First divergence	Sibling/data result	Decision
N01	Early failure return of initialized result; literal TRUE success return.	0xF0/12, nonbaseline	+0x4; queue still EBX, fail xor al,al	exact	reverted
N02	Literal TRUE return inside canonical success block; result only for trailing fail.	0xF0/12, 40adf3be...	+0x4	exact	no effect; reverted
N03	Add redundant !result to the success guard.	0xF0/12, 40adf3be...	+0x4	exact	predicate eliminated; reverted
N04	Union-overlay boolean result and long read_offset.	0xF0/12, 40adf3be...	+0x4	exact	scalarized; reverted
N05	Put initialized result first in declaration order.	0xF0/12, 40adf3be...	+0x4	exact	no effect; reverted
N06	_ReadWriteBarrier() immediately after false initialization.	0xF0/12, f803ad9d...	historical trace +0x6 (+0x7 under the later normalized reporter)	exact	prologue partly moves, false still folds; reverted
N07	N06 plus historical if (result && advance) writeback topology.	0xF0/12, 9ae0aa56...	+0x6	exact	wrong shared-tail topology; reverted
N08	Late switch(result) with distinct success/default returns.	0x100/12, ac2dc1a8...	+0x3	exact	spills result and emits switch machinery; reverted
N09	Replace N08 switch with if (result == TRUE).	0xF0/12, 40adf3be...	+0x4	exact	branch folds; reverted
N10	Switch directly on the runtime availability predicate.	0x100/12, 107cae55...	+0x4	exact	setle/switch code is not January; reverted
N11	N06 barrier plus N09 explicit outer success branch.	0xF0/12, f803ad9d...	+0x6	exact	no improvement over N06; reverted
N12	Barriers after false initialization and after success assignment.	0xF0/12, 1f080135...	queue remains in EBX	exact	no BL lifetime; reverted
N13	Scope read_offset and contiguous_size inside success block.	0xF0/12, 40adf3be...	+0x4	exact	no effect; reverted
N14	N13 plus register boolean result.	0xF0/12, 40adf3be...	+0x4	exact	hint ignored; reverted
N15	N14 plus full-function queue_reference alias.	0xF0/12, 40adf3be...	+0x4	exact	alias eliminated; reverted
N16	Use result++ on success.	0xF0/12, 40adf3be...	+0x4	exact	folded to canonical; reverted
N17	Store result in a one-byte local struct.	0xF0/12, 40adf3be...	+0x4	exact	aggregate scalarized; reverted
N18	Single-iteration do loop, failure break, success assignment.	0x150/17, 8e348c3ab923622446e3d5b4ff940cfd3e6466990d4e4aa793f8343d121e3f93	+0x5; 267 bytes	exact	creates target BL/EBX lifetime, but clones validator into the size path (+80 bytes/+5 relocs); reverted
N19	N18 plus noinline validator.	0xF0/12, 40adf3be...	+0x4	exact	removes both clone and desired lifetime; reverted
N20	N18 plus manually expanded size expression.	0x150/17, 8e348c3a...	+0x5	exact	same nested validator inline; reverted
N21	N20 validator call through a local function pointer.	0x100/12, 9339ad1b...	+0x4; 68 bytes	validator and exact caller cluster regress; data exact	closest dequeue body, but address-taking destroys target private EAX ABI; reverted
N22	N20 plus noinline validator.	0xF0/12, 40adf3be...	+0x4	exact	returns to baseline; reverted
N23	Single-iteration do ... while (result == FALSE).	0x150/17, 8e348c3a...	+0x5	exact	same nested-inline fixed point; reverted
N24	N23 plus noinline validator.	0xF0/12, 40adf3be...	+0x4	exact	returns to baseline; reverted
N25	N23 plus barrier at validator body entry.	0x150/17, 8e348c3a...	+0x5	exact	barrier cannot prevent cloned inline; reverted
N26	N23, noinline validator, barrier after false initialization.	0xF0/12, f803ad9d...	+0x7; 218 bytes	exact	N06 fixed point; reverted
N27	while(TRUE) with explicit failure and success breaks.	0xF0/12, 40adf3be...	+0x4	exact	simplified to canonical; reverted
N28	Explicit goto dequeue_done failure edge.	0xF0/12, 40adf3be...	+0x4	exact	simplified to canonical; reverted
N29	Force-inline helper returning false for initialization.	0xF0/12, 40adf3be...	+0x4	exact	helper folded; reverted
N30	Force-inline helper returning availability predicate.	0xF0/12, 40adf3be...	+0x4	exact	helper folded; reverted
N31	Declaration initializer plus inner advance and late success assignment.	0xF0/12, 40adf3be...	+0x4	exact	no effect; reverted
N32	Reverse comparison spelling to size >= data_size.	0xF0/12, bbe01e24...	+0x4	exact	wrong compare orientation, allocation unchanged; reverted
N33	Assign result before optional advance.	0xF0/12, c3d7f616...	historical trace retained only as success-tail divergence	exact	creates wrong shared success epilogue; reverted
N34	Force-inline validator wrapper plus N18.	0x150/17, 8e348c3a...	+0x5	exact	wrapper recursively inlines; reverted
N35	Ordinary static validator wrapper plus N18.	0x150/17, 8e348c3a...	+0x5	exact	wrapper inlines; reverted
N36	Move validator definition after reset, matching January symbol order.	0xF0/12, 40adf3be1fa79c0b9aaf6b169e37da2e59aa4e306efef68a9573b7aa7ec8dede	+0x4; 222 bytes	exact	definition order is not the missing control; reverted
N37	N36 definition order plus N18 loop.	0x150/17, 8e348c3ab923622446e3d5b4ff940cfd3e6466990d4e4aa793f8343d121e3f93	+0x5; 267 bytes	exact	exactly reproduces N18; reverted

Residual classification

Measured fact: target BL/EBX lifetime is reachable with this compiler (N18), but every legal-C shape found that creates it also changes the inliner fixed point and clones the validator, yielding 17 rather than 12 relocations. Preventing the clone—by noinline, a function boundary, or canonicalized control flow—simultaneously destroys the lifetime. Address-taking produces a much closer 256/12 dequeue but globally changes the validator's proven private ABI and regresses exact siblings.

The best classification is TU-context optimizer/inliner-allocation fixed point, not a proven compiler-QFE difference and not a semantic gap. Because the current residual has unequal padded sizes, it is research-parked here but is deliberately not admitted to config/parked.json under the stricter equal-size/equal-relocation parking rule.

Do-not-repeat list

• Do not retry declaration order/scope, register, local aliases, scalar unions/structs, result increment, reversed comparisons, or result-write placement.
• Do not retry single-iteration loops, while(TRUE), goto, early returns, shared tails, switches, or redundant predicates.
• Do not retry barriers at result or validator sites, validator noinline/forceinline/static wrappers, or manual size expansion.
• Do not take the validator's address: it invalidates the exact private ABI used by the rest of the translation unit.
• Do not retry function-definition order; both canonical and BL-producing control-flow shapes were measured.
• Do not use inline assembly, volatile byte forcing, undefined behavior, object-byte patches, altered optimization flags, or fuzzy credit.

Reopen criteria

Reopen only if one of these appears:

1. January source, line/scope records, or a genuine same-lineage C donor reveals a new control topology.
2. A strict-exact donor demonstrates BL/long-register lifetime reuse without changing an exact private helper ABI.
3. A distinct authentic Bungie-era VC7 13.00.9254 compiler binary improves unchanged source.
4. A tested general compiler control can prevent nested cloning without forcing noinline or address-taking.

Disposition

The safe source is restored and remains 7/8 strict exact with 251/251 owned data bytes exact. circular_queue.obj is not Matching and receives no object credit. The residual is evidence-exhausted under current provenance and parked at the research level pending one of the explicit reopen criteria.