[db] Add --snapshot-format to choose the layout a dump writes

[maxkozlovsky]

A loader takes a stream with or without a header, but a binary that predates the header aborts on one, so a node that always writes headers cuts off every consumer that has not upgraded yet. Give monad-cli --snapshot-format so a publisher can keep writing the pre-header layout (v0, the default) while its own loader still accepts both, and move to v1 once every consumer understands it.

A format is stamped verbatim into the header's version field, so the dump rejects one it does not know before writing anything: otherwise a stale enumerator would leave a complete, checksummed snapshot that no reader accepts, and the failure would surface at restore.

v0 writes the records alone: stream for stream it is a v1 dump minus the header, which SnapshotFormatV0OmitsStreamHeaders pins by dumping the same database both ways, and which Basic now exercises end to end by restoring a v0 dump of a slot-encoded source.

[Copilot]

🟡 Changes recommended

The new parameter changes an extern "C" function signature without preserving or coordinating the existing ABI.

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Pull request overview

Adds selectable snapshot dump layouts, defaulting to headerless v0 for compatibility with older consumers.

Changes:

• Adds --snapshot-format with v0/v1 validation.
• Makes the writer emit headers only for v1.
• Adds v0/v1 dump comparison and restore coverage.

Verdict: NEEDS CHANGES
🤖 Generated with Claude Code

File summaries

File	Description
cmd/monad_cli.cpp	Adds the CLI format option and logging.
category/execution/ethereum/test/test_db_snapshot.cpp	Tests both layouts and v0 restoration.
category/execution/ethereum/db/db_snapshot.h	Defines formats and updates the dump API.
category/execution/ethereum/db/db_snapshot.cpp	Validates formats and conditionally writes headers.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 1
• Review effort level: Lite

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[github-actions]

Review summary

Reviewed the single commit (8f3c86f) adding --snapshot-format to monad-cli and threading monad_snapshot_format through monad_db_dump_snapshot. The change is well-constructed:

• Format validation — check_snapshot_format rejects an unknown enumerator before the dump opens the database, and the default-less switch turns a future enumerator into a -Wswitch build error at both dispatch sites (db_snapshot.cpp, snapshot_format_name in monad_cli.cpp).
• Version coupling — the static_assert(MONAD_SNAPSHOT_FORMAT_V1 == MONAD_SNAPSHOT_STREAM_VERSION) pins the format enum to the stream header version, so they cannot drift apart silently.
• Offset invariance — account_bytes_written_ counts from the first record rather than the stream start, so storage-record offsets are identical in v0 and v1 layouts; the loader is unchanged and its magic-sniffing already handles both.
• Callers — all in-repo callers of monad_db_dump_snapshot were updated; the header is not consumed by the Rust crates, so no bindgen impact.
• Tests — SnapshotFormatV0OmitsStreamHeaders pins v0 = v1 minus headers and restores a v0 dump end to end; Basic now exercises v0 through the checksum-verifying filesystem loader. One [P3] inline note on a failure-path out-of-bounds read in the new test.

The default of v0 (headerless) and the reader's accept-only-v1-or-headerless policy are both deliberate per the PR description and documented in the enum comment, so they are not flagged.

Verdict: CORRECT

🤖 Generated with Claude Code