Drew T
2.5 KiB
§384 ★★★ — A CARVE-CONFIG BANK IS RED UNTIL YOU RE-EXTRACT, AND THAT LOOKS EXACTLY LIKE A FALSE BANK (P31 S69; measured twice, cost one destroyed match)
The symptom. A gate banks a jtbl function, commits, and reports green. You then verify the
binary in the main tree with make build BINARY=<b> and get a SHA mismatch:
[FAIL] build/ov_SC04_011/ov_SC04_011
got 9c94d36a2cb5d8b56073d859c6e58cf396a5e750
want 8bc09c422de2c28b3d71cf382cb6241c1e39d5db
Every instinct says false bank. It is not. Both times it happened in S69, the bank was byte-perfect:
make extract BINARY=ov_SC06_025 && make build BINARY=ov_SC06_025 -> BYTE-IDENTICAL
make extract BINARY=ov_SC04_011 && make build BINARY=ov_SC04_011 -> BYTE-IDENTICAL
The mechanism. Banking a jtbl function changes CARVE CONFIG — JTBL_PADS in
config/overlays.mk and the binary's splat yaml (tables=+0x0,+0x20,+0x40,+0x58 gaining a fifth
entry). Those files are splat inputs: asm/ and the linker script are generated from them. A
worker gates inside a worktree that regenerated its own state, so it is right. The main tree, after
the merge, holds NEW carve config against OLD extracted state — and links the newly-carved C against
a stale .ld. The SHA that comes out is meaningless.
The trap inside the trap. Reverting the C alone makes it worse and changes the error, which reads like progress:
jtbl_rodata_pads: consumed 4 rodata jump table(s) but 5 pad spec(s) given — table-count drift vs the carve
That is the src and the carve state disagreeing — you reverted half a commit. A carve revert must
carry config/ too (see the carve-state-files-never-blanket-add discipline).
The law. Verification after a gate must regenerate whatever that gate changed the inputs to. Concretely:
| the gate touched | the valid per-binary check |
|---|---|
src/ only |
make build BINARY=<b> |
anything under config/ |
make extract BINARY=<b> && make build BINARY=<b> |
This is the R22 corollary aimed the other way. R22 says a reverted config needs a re-extract; a
landed config change needs one just as much. It is also R40 in its purest form — the instrument
(a build over stale extract state) was broken, and I attributed the failure to the subject, reverted
a legitimate 96-line match, and wrote a checkpoint calling it a false bank. The give-away I ignored:
the commit's own diffstat showed config/overlays.mk and a splat yaml right next to the .c.