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:

```asm
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.