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

breakable_surfaces.obj exact-match strategy log

Scope and provenance

• Source TU: source/physics/breakable_surfaces.c
• Target object: source/physics/breakable_surfaces.obj
• Target build: Halo January 2002 Xbox build
• Compiler: XDK 3911 Microsoft C/C++ 13.00.9254.1
• Flags: /O2 /Oy- /Ow /QIfist /DDEBUG /Dxbox
• Comparator: hardened COFF function and section comparison
• Status: active closeout lane; no matching credit has been granted

The rough October source at C:\Users\isabe\Downloads\halo-main (1)\halo-main\src\halo\physics\breakable_surfaces.c is a topology hint only. January machine code, relocations, and data ownership remain authoritative.

Current validated state

• Functions: 11/12 strict exact.
• Only residual: _breakable_surface_effect.
• Target/current padded size: 0xFC0/0xFC0 (4032/4032).
• Target/current relocations: 117/117, with the same semantic destinations.
• Target/current frame: 0x1240/0x1230.
• Target normalized SHA-256: 510486a7d0a1f2fc1dfb8f0c47990c57f83ce1030ef5e4db8dfc42943dc56bfa
• Current normalized SHA-256: fcf66a3ce196b5295b412824a98f874123effcdf9f3043e6a1cd9bb98bfcaef2
• All 11 protected sibling functions remain strict exact.

The current source is the E09 traversal/audio scratch union plus the E18 rectangle2d grid_bounds shape. It was rebuilt from source under the canonical flags after all later analysis-only experiments were reverted.

Accepted controls retained in source

E09: traversal/audio scratch union

January reuses one 0x58-byte region for traversal scratch and the later sound_location. The retained C89 union models the measured layout:

• traversal s_offset, t_offset, two projected points, and eight 2D vertices;
• audio view with sound_location at union offset 0x2C;
• both views end at the same byte.

This is defined lifetime-based storage reuse, not aliasing or byte padding.

E18: rectangle2d grid bounds

Replacing four unrelated short locals with rectangle2d grid_bounds moved the candidate from 0xF90 to the exact target size 0xFC0 while preserving 117/117 relocations and every exact sibling.

The native structure layout is exactly the order proved by January:

Structure field	January meaning	January home
grid_bounds.y0	t_min	-0x5C
grid_bounds.x0	s_min	-0x5A
grid_bounds.y1	t_max	-0x58
grid_bounds.x1	s_max	-0x56

This is an evidence-backed type recovery and remains in production even though the function is not yet exact.

Current stack/codegen finding

E18 makes every large aggregate start exactly 16 bytes above the January home:

Region	Target	E18
surface_queue[1024]	-0x1240	-0x1230
surface_vertices3d[8]	-0x240	-0x230
traversal/audio scratch	-0x1E0	-0x1D0
new_particle_data	-0x188	-0x178

The missing 16 bytes are four January dword integer-conversion homes. For each grid bound January emits:

call  _ceil/_floor
fstp  dword ptr [ebp-real_home]
add   esp, 8
fld   dword ptr [ebp-real_home]
fistp dword ptr [ebp-distinct_integer_home]
mov   r16, word ptr [ebp-distinct_integer_home]
mov   word ptr [ebp-grid_bound], r16

E18 instead emits fistp qword to one shared compiler temporary. The target therefore rounds through single precision and owns four distinct dword conversion homes; the present compiler forwards through every normal readable-C spelling tested.

Experiment matrix

Every reverted experiment preserved all 11 exact siblings unless explicitly noted.

ID	Source or compiler experiment	Result	Decision
E01	Move position and position_2d_test inward	byte-neutral	reverted
E02	Move both vertex arrays into the while scope	byte-neutral	reverted
E03	Declare the 2D vertex array later	byte-neutral	reverted
E04	Remove the duplicate queue-read shadow	byte-neutral	reverted
E05	Hoist random offsets to function scope	byte-neutral	reverted
E06	One named real between ceil/floor and cast	byte-neutral; store forwarded	reverted
E07	Group grid bounds and loop indices	byte-neutral	reverted
E08	True sibling traversal/audio scopes	frame 0x1228; proved lifetime reuse	superseded by E09
E09	Meaningful 0x58 C89 scratch union	size 0xF90, frame 0x122C	retained
E10	Remove explicit long from the grid casts	byte-neutral	reverted
E11	Static grid-index helper	caller byte-neutral; unwanted helper COMDAT	reverted
E12	Named real plus four named long homes	optimizer eliminated homes	reverted
E13	Aggregate containing rounding/conversion fields	optimizer eliminated homes	reverted
E14	Address escape / compiler-barrier shape	did not produce target chain	reverted
E15	Conversion-home array plus barrier	did not produce target chain	reverted
E16	Pointer helper plus barrier	did not produce target chain	reverted
E17	__forceinline float ceil/floor wrappers	caller byte-neutral; two unwanted COMDATs	reverted
E18	Native rectangle2d grid_bounds	exact 0xFC0, 117/117; correct bound layout	retained
E19	real_rectangle2d staging plus E18	byte-identical to E18	reverted
E20	Four named long homes plus E18	byte-identical to E18	reverted
E21	Historical function-scope bounds plus long loop indices	regressed to 0xF70; hash f32f3d8f...	reverted
E22	Move only rectangle2d grid_bounds to function scope	byte-identical to E18	reverted
E23	Change only the two grid loop indices to long	same 0xF70 regression as E21	reverted
A01	Compile E18 as C++ (/TP)	function byte-neutral; decorated symbols	analysis only
A02	/TP with explicit ceilf/floorf	unwanted helpers; caller byte-neutral	analysis only
A03	Remove /Ow	byte-neutral	analysis only
A04	Enable /Op	4320 bytes, 114 relocs; broad regression	rejected
A05	Minimal direct/named/four-value float-to-short fixtures	every form collapsed to shared fistp qword; no target motif	analysis only
A06	Four legal union-backed long/short conversion objects	also collapsed to shared fistp qword	analysis only

Corpus and compiler audits

• A relocation-aware scan of all 833 January split objects found the complete float-home conversion motif only eight times: four here and four in nonexact _build_structure_lens_flares.
• A scan of 467 rebuilt base objects found zero occurrences.
• _build_structure_lens_flares is not a reconstructed-C donor: target/base is 4336/4000 bytes and 156/157 relocations.
• All locally available compatible compiler sets are byte-identical VC7 13.00.9254.1 binaries. No alternate compatible compiler/QFE is locally available.
• Upstream history commit 95e6477328dd7742175074de5eab0a20c3e7bde0 provided a real source-shape lead: function-scope bounds and long grid indices. E21-E23 showed that bound scope is neutral and the historical long index type causes the same 0xF70 regression, so it is not the January topology.
• The reproducible round_probe.c fixture proves that direct, named-real, named-long, four-output, and four-longs-first forms all lower through one shared fistp qword home under the campaign compiler.

Reproducible evidence is under research/breakable_surfaces_closeout/, especially STACK_SLOT_LIFETIME_MAP.md and donor_census/REPORT.md.

Do not repeat

• E01-E17 and E19-E23, including cosmetic variations with equivalent lifetimes.
• C++ mode, ceilf wrappers, /Ow removal, or /Op.
• Adding guessed padding merely to force the missing 16 frame bytes.
• Treating _build_structure_lens_flares as an exact donor.
• Inline assembly, volatile byte forcing, undefined behavior, object-byte patches, or compiler-flag changes.

2026-07-28 provenance audit: January PDB, HCEX PDB, and local source corpus

A second provenance pass found a strong source-semantics lead but no new legal-C code-generation lever.

January PDB negative result

C:\Users\isabe\Downloads\Halo Combat Evolved (Jan 14, 2002 prototype)\cachebeta.pdb names \halo\objects\halobetacache\breakable_surfaces.obj as module stream 154. The complete module stream is only 132 bytes: one S_OBJNAME record, one compiler record (Microsoft (R) Optimizing Compiler), and four zero tail bytes. It contains no function, local, type, or line records, so it cannot recover the grid-bound declarations, any rounded real, or the four conversion homes. The raw compiler record must not be treated as proof of an unrecorded precision flag.

HCEX source-line and code-generation evidence

The later debug and release symbol files are:

• C:\Users\isabe\Documents\Codex\2026-07-13\i-w\research\hcea_jun2011_prototype\payload\Halo CE Anniversary (Jun 24 2011)\HCEX.pdb
• C:\Users\isabe\Documents\Codex\2026-07-13\i-w\research\hcea_jun2011_prototype\payload\Halo CE Anniversary (Jun 24 2011)\HCEX_Release.pdb

They identify breakable_surface_effect as source d:\projects\code\hcex\sources\physics\breakable_surfaces.c, source MD5 CEACA3EE6F74879855CD2005D8B6C1AC. Debug RVA/length/frame are 0x00D0C1A0/0xE68/0x1360; release RVA is 0x01743190 with the same length/frame. Neither PDB contains injected source.

DIA line records map the four bounds to four consecutive source statements: lines 423-426 are the two ceil assignments followed by the two floor assignments; line 421 is the nonzero-density test and line 440 begins the grid loop. There are no intervening source lines for a separate named-real assignment/conversion pair. The surviving named-local records also contain no rounded-real/grid aggregate or scalar grid-bound names, although optimized-away locals cannot be ruled out from that absence alone.

PowerPC disassembly of the decoded debug image at flat RVA 0xD0C924 is stronger semantic evidence. Each libm result is immediately rounded from double to float with frsp (first at 0xD0C954), then converted with fctiwz/stfd and sign-extended to a short; the four results remain scalar GPR values. This is consistent with four direct (short)(real)ceil/floor(...) assignments and inconsistent with a required separate named real statement. PowerPC cannot distinguish the optional intermediate (long) because both int and long are 32-bit there.

Source-corpus and macro negatives

A hash census of 747 local breakable_surfaces.c files found 11 unique contents and no copy matching HCEX MD5 CEACA3EE6F74879855CD2005D8B6C1AC. Repository history contains reconstruction commits only, not an authentic Bungie source blob. The October file at C:\Users\isabe\Downloads\halo-main (1)\halo-main\src\halo\physics\breakable_surfaces.c is a decompiler reconstruction: it defines replacement breakable_floor and breakable_ceil functions and has grid comments/order inconsistent with the machine-code topology, so its named float val is not provenance.

The active type and macro audit found typedef float real in source/math/real_math.h and ordinary ternary PIN in source/cseries/cseries.h; no real-to-short rounding macro exists in the recovered source. The closest source sibling, source/structures/structure_lens_flares.c, spells all four bounds directly as (short)(real)ceil/floor(PIN(...)), and its January target has the same float-home conversion motif, but that function is itself nonexact and cannot serve as a strict donor.

Verdict and do-not-repeat expansion

The highest-likelihood original spelling is four direct scalar assignments with an explicit (real) cast, probably without the reconstruction-only (long). That spelling, named-real forms, named-long homes, aggregates/arrays, address escapes, helpers/wrappers, scope changes, C++ mode, and precision-flag probes have already been measured and do not make the campaign VC7 emit January's chain. No genuinely untried legal-C hypothesis now satisfies the reopen criterion. Do not repeat the January-PDB private-record search, HCEX injected-source/source-hash search, October-source audit, macro/type audit, or local source-hash census; reopen only if an authentic source blob, a distinct compatible compiler/QFE, or a strict donor artifact appears.

Residual classification

Compiler-precision/provenance fixed point. Size, call set, relocation count, recovered grid type, and large aggregate layout are strongly supported. January has a repeated single-precision rounding and four-home conversion topology that the current VC7 binary does not emit from any tested legal-C shape. This is not strict exactness and receives no completion credit.

Reopen/continuation criteria

Reopen only with evidence for one of:

1. an original October/January/HCEX source or debug topology that explains the intermediate real materialization;
2. a strict reconstructed-C donor for the complete conversion motif;
3. a genuinely new legal-C dataflow that predicts both the fstp/fld single-precision round trip and four distinct dword homes.

Disposition

NonMatching / rigorously parked at 11/12 exact functions. The retained E09 and E18 changes are an evidence-backed improvement checkpoint, not an object completion. Do not mark the object complete or grant credit from equal size or semantic plausibility. Reopen only if an authentic source blob, a distinct compatible VC7/XDK compiler or QFE, or a strict reconstructed-C donor becomes available.