docs(roadmap): source-to-object provenance spine — DWARF (#394) + MC/DC traceability (#396) - #395
Merged
Conversation
…-2 gated on VCR-RA value→location map synth drops all DWARF (zero .debug_* in output) → bare-metal images aren't source-debuggable. The input wasm carries it and meld already remaps it through fusion (meld-core/src/dwarf.rs); synth is the only stage that drops it. Tractable: synth's source_line threading (~220 sites) is the (machine-addr → wasm-offset) half — compose with the wasm DWARF for (machine-addr → source). Two tiers: Tier 1 .debug_line (machine-addr → source line; raw material ready; regalloc-independent) → breakpoints/backtraces; Tier 2 .debug_info variable locations gated on the VCR-RA value→location mapping (the same (pc,local)→ARM-vreg map surfaced in VCR-RA-010). DWARF is additive non-loadable sections ⇒ frozen fixtures bit-identical. Coordinate encodings with meld end-to-end. Docs only — no code, frozen-fixture-safe. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
#396); shares the DWARF provenance spine witness measures MC/DC on wasm branches; synth's wasm→ARM lowering changes the branch set (fold→predication / eliminate-constant / split), so wasm-level MC/DC doesn't 1:1 represent the object code (DO-178C 6.4.4.2). Three directions: fold (safe — wasm MC/DC authoritative), eliminate (justified by scry's constant-condition evidence), split (the one that adds object obligations). Fix = the SAME decision-provenance map as VCR-DBG-001 (#394): one mechanism (the source_line threading already present), two consumers — debugger (DWARF) + coverage reconciler (witness). Bundled with the DWARF artifact because they share the source-to-object provenance spine. Coordinate with witness + scry. Docs only — frozen-fixture-safe. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
avrabe
changed the title
Codecov Report✅ All modified and coverable lines are covered by tests. 📢 Thoughts on this report? Let us know! |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Tracks two issues that share one mechanism: synth must emit a source-to-object provenance map (it already threads
source_line= wasm-op-index per ARM instruction). One spine, two consumers — the debugger and the coverage reconciler.VCR-DBG-001 — emit DWARF (#394)
synth emits zero DWARF → bare-metal output isn't source-debuggable. The input wasm carries it and meld already remaps it through fusion (
meld-core/src/dwarf.rs); synth is the only stage that drops it. Tier 1.debug_line(machine-addr → source line) is regalloc-independent and ready; Tier 2.debug_infovariable locations is gated on the VCR-RA value→location map.VCR-COV-001 — MC/DC source-to-object traceability (#396)
witness measures MC/DC on wasm branches; synth's lowering changes the branch set (
select→cmov, #390 pass-4 fusion, i64-cmp,br_table), so wasm-level MC/DC doesn't 1:1 represent the object code (DO-178C 6.4.4.2). Three directions:The fix is the same decision-provenance map: classify each wasm decision →
{1:1 | folded | eliminated(+scry) | split}; a reconciler in/alongside witness makes the truth table defensible against the object code.Why bundled
Both are "synth emits source-to-object provenance." Building the map once serves DWARF line/var info and the coverage reconciliation — they shouldn't drift into two mechanisms.
Docs only; frozen-fixture-safe (the map is emitted metadata, not a codegen change); rivet 0 non-xref.
🤖 Generated with Claude Code