BFM-decomp/cookbook/C0160.md

§149 — Four instrument defects in one session, and the two questions they were hiding (P30 S43)

Not a codegen section. Every item here was recorded in a previous session as a property of the CODE; each turned out to be a property of a TOOL. That is now the fourth consecutive session with that shape (§53 carve · P28's B2 · P27's five · this), so the pattern below is the reusable part.

A. A prep step that returns its input on failure is indistinguishable from a search that found nothing

p16_permute.make_base_c ran cpp_expand_macros before #include lines were dropped, so cpp -P -nostdinc - died on common.h, and return c handed back the UNEXPANDED draft. hide_asm then ate the gte_* macro block and the function with it; decomp-permuter reported "Function not found in base.c" and no-opped in 0 s. §148 recorded that as "the GTE #define block defeats make_base_c — demacroize first." It was a two-line ordering bug, and it had silently disabled the permuter on 63 stored drafts, including the behemoth renderer drafts — the highest-byte-weight targets we have.

Rules: a permuter run that reports no match in ~0 s is a TOOLING verdict until base.c is inspected. And prefer an assertion on the OUTPUT (defines_fn: the definition must survive into base.c) over a fix for the one cause you found — the output check catches the comment-eating class, this cpp class, and the next macro shape, for free.

Consequence worth generalising: a hand-search floor measured while a tool was silently broken is not a floor. Here the ~40-probe "unmovable 63" fell to 42 the moment the permuter could run.

B. Same address + same name ≠ same body — and the ledger keys on address

0x8017C6F4 is a 15-instruction function in ov_SC03_010/011/013 and a 948-instruction renderer in ov_SC03_126/003, ov_SC04_021, ov_SC05_019. backlog.load_best() keyed on address alone and kept the lower absolute closeness, so a 14-of-15-wrong draft (7% correct) masked a hand-won 63-of-947 (93% correct) and the giant vanished from render, the grinder, and target selection. Sub-key by known nins; different sizes are different bodies.

Two corollaries, both live:

• closeness is an absolute mismatch count and is NOT comparable across sizes. 14/15 outranks 63/947 in every ranking we have. (A relative rank was probed and NOT built: only 24 of 836 live rows carry both closeness and nins. Revisit when coverage rises.)
• binary: null → defaults to ov_SC01_077 → "not an open stub there" was read as "banked". When the function does not EXIST in the defaulted binary, absent was being scored as done (R32/R34). Derive the binary from the draft path; drop a row only when the fn is closed everywhere it exists.

C. make: *** [...] Error N is a summary, never a diagnosis

classify_fail took errs[-1], and make prints its own failure summary last, always — so the wrapper won every time. ~3,000 of ~4,000 CC1-FAIL labels in the committed .classified.txt corpus say nothing but the TU name the record already stores, which is why diagnosing one cost a manual splice-and-rebuild. Exclude make's lines; take the FIRST real diagnostic (cc1 cascades — error #1 is the cause, error #N the aftershock); label a wrapper-only failure CC1-FAIL(no-diagnostic) rather than disguising it. Same family as the §58 warning red-herring guard directly above it in the source: a label identical for every input carries no information.

D. "Cheap fuel" that was never probed: 0 of 31 templatable

Three sessions carried "26 unpropagated members, the recovery ladder has every lever, ~0 tokens." Scanned all 31 (not sampled): a mechanical family_remap from every matched source binary fails on 31 of 31, with gross reloc-count mismatches (2!=15, 11!=20, 2!=0). They are structurally distinct bodies sharing an address — B's collision, one level down — and family_hseq independently agrees (matched=0, several n_members=1). Nothing to template from ⇒ never plumbing, always per-member drafting.

The estimating rule this proves (R37's own failure mode): a work item carried across sessions with a token price attached and no probe behind it is a guess wearing a number. Probe one member before it is scheduled — the probe here cost minutes and removed a phantom item from the board.

Symptom lines for the index: "the permuter found no match in 0 seconds" · "a wall that only one tool reports" · "a backlog row that outranks a better result" · "CC1-FAIL: make: *** Error N" · "cheap fuel nobody has probed".

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