path_structure_bsp.obj — structure_surface_index_from_point

This isolated lane reconstructs only structure_surface_index_from_point from the January 14, 2002 target. The remaining five object functions are intentionally absent and are owned by the parent atomic-object lane.

Target evidence

Padded size: 0x60 (96 bytes); meaningful size: 82 bytes.
Relocations: one REL32 call to _structure_test_line2d at function offset 0x28.
The target has three distinct returns: immediate NONE, fallback to known_surface_index, and the recovered surface index. Multiple returns are retained because they are required by the January control flow, despite the project's general preference for a single return.
The stack local is a 0x1c-byte path_collision_result; its point begins at offset +0x04, and its surface index is at +0x10.

Experiments

E1 — HCEA topology with January-authoritative types

Shape: guard return for known_surface_index == NONE, one line-test call, copy the resulting 2D point, then fallback/result returns.
Source provenance: HCEA supplied the control-flow hypothesis; January bytes independently proved every parameter, stack offset, call argument, and return.
Result: size and relocation count matched (0x60, 1), but the call relocation landed at +0x2f instead of +0x28. VC7 placed the immediate NONE return before the body, adding a seven-byte early epilogue that January places after the body. Rejected.

E2 — positive body guard, trailing `NONE` return

Shape: wrap the line-test body in if (known_surface_index != NONE), keep the fallback return within it, and put the NONE return after the guarded body.
Prediction: this preserves the same three semantic exits while putting the immediate-NONE materialization after the body, as required by the target CFG.
Result: strict exact. Target/candidate padded size 0x60; relocation count 1/1; call relocation address/type/destination/addend equal at +0x28; both normalized SHA-256 values are 29cfb8955fc45cfc7972505dddb757d4374ca33735024c18aa7f5baac71b8f49.

Verification

ninja build/base/source/ai/path_structure_bsp.obj
python -m tools.coff_compare build/split/source/ai/path_structure_bsp.obj \
  build/base/source/ai/path_structure_bsp.obj \
  _structure_surface_index_from_point

The hardened comparator returned all_equal: true. No data sections are owned by this function-only lane. Whole-object admission remains the parent lane's responsibility after the other five functions and shared data are reconstructed.

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