docs: memo on wasmtime FACT reusability for Christof Petig#105
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Rethinks the claim that meld's fact.rs cannot be used from wasmtime. The honest conclusion is "cannot be dropped in as-is" — much weaker than "the emission logic is unshareable." The pure emission core (transcoders, list copies, record lift/lower, helpers like emit_checked_realloc) is shareable; ~1500 LOC could become a third crate that both meld-core and wasmtime-environ depend on. Also notes that LS-A-7 (the realloc overflow + null-check audit we just landed across 19 sites) is likely reproducible on wasmtime FACT, since both have the same emission pattern. Drafted for Christof Petig as a starting point for a possible collaboration discussion. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Memo at `docs/wasmtime-fact-reusability.md` rethinking whether meld's `adapter/fact.rs` can be reused from wasmtime.
The original claim was "cannot be used from wasmtime." Christof Petig was rightly skeptical even after seeing our work. After rereading both code-bases (meld's fact.rs vs wasmtime-environ's `src/fact/`), the honest conclusion is:
Includes a side-by-side architectural comparison, the equivalent function table, and three options for sharing (third crate, meld imports wasmtime FACT, wasmtime imports meld). Recommends the third crate.
Bonus observation: the LS-A-7 audit we just landed (19 realloc sites missing overflow + null guards) is likely reproducible against wasmtime FACT — same emission pattern, same likely missing guards. Worth flagging upstream.
Test plan
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