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fix(ssz): drop redundant default-init pass in fixed-list decode - #468

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Jul 7, 2026
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fix(ssz): drop redundant default-init pass in fixed-list decode#468
wemeetagain merged 1 commit into
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@GrapeBaBa GrapeBaBa commented Jul 7, 2026 •
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What

FixedListType.deserializeFromBytes pre-filled the entire output slice with default_value before the element loop overwrote every element — a full extra write pass over the output (128 MB for a 1M-validator validators list).

Why it is safe to remove

  • FixedListType elements are comptime-enforced fixed-size, and all fixed-size SSZ types are plain data with no allocator-owned memory.
  • The decode loop writes every element completely; there is no skip path.
  • On a mid-loop error, the caller's unconditional deinit only frees the list buffer — it never reads element contents — so undefined trailing elements are never observed.
  • VariableListType keeps its init pass: its element deinit does read element contents, so every slot must stay valid across a mid-loop failure.

vector.zig's decode path already follows this pattern (no init pass, same reasoning).

Measured

Full-state decode, libssz differential fixture (phase0 BeaconState), ReleaseFast:

machine cold warm (reused capacity)
AMD EPYC 7763 (Linux) 40.8 ms → 17.5 ms (−56%) 28.8 ms → 8.7 ms (−69%)
Apple M5 (macOS) 8.4 ms → 7.1 ms (−16%) 8.6 ms → 6.8 ms (−21%)

encode and hashTreeRoot unchanged (control).

@GrapeBaBa
fix(ssz): drop redundant default-init pass in fixed-list decode
bba608b 
FixedListType.deserializeFromBytes pre-filled the entire output slice with
default_value before the element loop overwrote every element. Fixed-size
elements are plain data: the loop writes each element fully, and on error the
caller's unconditional deinit only frees the list buffer without reading
elements, so the init pass protected nothing. VariableListType keeps its init
pass: its element deinit reads element contents, so mid-loop failure requires
every slot to be valid.

Measured on the libssz differential fixture (phase0 BeaconState, 1M
validators), decode of the full state:

- AMD EPYC 7763 (Linux, ReleaseFast): 40.8 ms -> 17.5 ms cold, 28.8 ms ->
  8.7 ms with reused capacity
- Apple M5 (macOS, ReleaseFast): 8.4 ms -> 7.1 ms cold; ReleaseSafe warm
  8.3 ms -> 6.5 ms

zig build test:ssz passes.
@GrapeBaBa
GrapeBaBa requested a review from a team as a code owner July 7, 2026 10:22
wemeetagain
wemeetagain approved these changes Jul 7, 2026
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Good catch. LGTM, reasoning looks sound

@wemeetagain
wemeetagain merged commit 0c757be into main Jul 7, 2026
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@github-actions github-actions Bot mentioned this pull request Jul 30, 2026
Merged
@wemeetagain
wemeetagain deleted the gr/fix-fixed-list-decode-init branch August 17, 2026 19:39
wemeetagain pushed a commit that referenced this pull request Aug 19, 2026
@github-actions
chore: release 1.0.0 (#536)
a19d746 
🤖 I have created a release *beep* *boop*
---


##
[1.0.0](v0.1.2...v1.0.0)
(2026-08-19)


### Features

* add `state.getBuildersLength()` binding
([#472](#472))
([be2b5ab](be2b5ab))
* **beacon-node:** add block state cache and checkpoint datastore
([#452](#452))
([2145faa](2145faa))
* bindings to `getExpectedWithdrawals` and native tweaks
([#350](#350))
([f47bc66](f47bc66))
* **bindings:** add pubkey cache syncPubkeys
([#537](#537))
([542779f](542779f))
* **bindings:** aggregate cached public keys by validator index
([#397](#397))
([2f90603](2f90603))
* **bindings:** align `BeaconStateView` with `IBeaconStateView`
([#347](#347))
([b8ec273](b8ec273))
* **bindings:** configurable pubkey cache growth step
([#481](#481))
([133ef24](133ef24))
* **bindings:** expose more APIs for STF
([#444](#444))
([7fe2609](7fe2609))
* **bls:** add small MSM for npoints < 32
([#393](#393))
([b430638](b430638))
* **blst:** use external buffers for blst operations
([#358](#358))
([78e4678](78e4678))
* **ci:** conditionally publish bindings with tag
([#355](#355))
([ea77919](ea77919))
* **clock:** add clock module for slot/epoch timing
([#354](#354))
([385b077](385b077))
* **fork_choice:** add Prometheus metrics module
([#309](#309))
([cbc9d8d](cbc9d8d))
* **forkchoice:** implement the forkchoice module
([#246](#246))
([7c62a9b](7c62a9b))
* getSyncCommitteesWitness
([#367](#367))
([ef77649](ef77649))
* implement `loadState` API and binding
([#165](#165))
([f903519](f903519)),
closes [#159](#159)
* **metrics:** metrics bindings
([#455](#455))
([dd41999](dd41999))
* migrate blst,pubkeys to use zapi js dsl
([#331](#331))
([fcd26ca](fcd26ca))
* **pubkeys:** add getPubkeyBytes binding
([#555](#555))
([4ca51cf](4ca51cf))
* publish ARM64 musl bindings
([#482](#482))
([ac764c9](ac764c9))
* **shuffle:** add swap-or-not shuffling module and binding
([#559](#559))
([c2db37c](c2db37c))
* split nextValue fn
([#464](#464))
([b47faeb](b47faeb))
* support getLatestWeakSubjectivityCheckpointEpoch
([#366](#366))
([dcf3883](dcf3883))
* update fulu deposit processing
([#442](#442))
([064335c](064335c))


### Bug Fixes

* avoid set ([#484](#484))
([2e25d97](2e25d97))
* better generation of rand scalar
([#388](#388))
([74dce77](74dce77))
* **bindings:** accept `dontTransferCache` in processSlots for backward
compatibility
([#460](#460))
([65df5af](65df5af))
* **bindings:** check signature infinity by default
([#509](#509))
([2f5f281](2f5f281))
* **bindings:** clean up failed async BLS work
([#527](#527))
([1111b00](1111b00))
* **bindings:** free metrics writer on scrape failure
([#529](#529))
([4c8d94a](4c8d94a))
* **bindings:** harden random aggregate scalars
([#528](#528))
([8e89a63](8e89a63))
* **bindings:** log level for missing fields
([#435](#435))
([08faf41](08faf41))
* **bindings:** misordering of print for cpu count
([#381](#381))
([752a972](752a972))
* **bindings:** populate epoch participation for test fixtures
([#436](#436))
([8dbdd2e](8dbdd2e))
* **bindings:** refcount Pool to fix teardown panic
([#352](#352))
([23b2f68](23b2f68))
* **bindings:** roll back partial N-API initialization
([#491](#491))
([31c5ebb](31c5ebb))
* **bindings:** size BLS thread pool by cgroup-aware CPU count
([#386](#386))
([3ae9522](3ae9522))
* **bindings:** validate class types before unwrap
([#514](#514))
([2fd2ad5](2fd2ad5))
* **bindings:** validate secret key hex length
([#517](#517))
([136e415](136e415))
* **bls:** align PublicKey.uncompress validation with
Signature.uncompress
([#508](#508))
([5a8dbe9](5a8dbe9))
* **bls:** bound randomized aggregation inputs
([#548](#548))
([779d0bf](779d0bf)),
closes [#542](#542)
* **bls:** clean up partial thread pool initialization
([#490](#490))
([d55e598](d55e598))
* **bls:** convert pippenger scratch bytes to element counts
([#513](#513))
([a12ca92](a12ca92))
* **bls:** enforce 32-byte signing roots
([#545](#545))
([72fd308](72fd308))
* **bls:** make batch cardinality structural
([#547](#547))
([a06d8b2](a06d8b2))
* **bls:** preserve aggregate outputs on failure
([#521](#521))
([e0b6dd1](e0b6dd1))
* **bls:** reject empty keygen salts
([#524](#524))
([d2a9c86](d2a9c86))
* **bls:** reject unknown BLST error codes
([#525](#525))
([9e4a6ad](9e4a6ad))
* **bls:** size pairing buffers for 32-bit targets
([#531](#531))
([dc64a27](dc64a27))
* **blst:** default signature infinity check to true if not provided
([#387](#387))
([021cdcb](021cdcb))
* **build:** remove `zig-out` from `files`
([#360](#360))
([c52af09](c52af09))
* **ci:** fix caching spec test version
([#439](#439))
([96885a1](96885a1))
* dangling state pointer in loadOtherState
([#450](#450))
([81cbd5f](81cbd5f))
* **epoch_cache:** compute missing `next_proposers`
([#447](#447))
([0088a29](0088a29))
* **epoch_cache:** populate decision roots in afterProcessEpoch
([#453](#453))
([4b70a5e](4b70a5e))
* export asyncAggregateWithRandomness through napi binding
([#371](#371))
([1d04c2b](1d04c2b))
* harden memory safety across PMT, SSZ tree views, and state transition
([#377](#377))
([d6f5897](d6f5897))
* improve atomic ordering in ThreadPool and NAPI init
([#310](#310))
([4b0a1cc](4b0a1cc))
* interface compatbility with NativeBeaconStateView
([#445](#445))
([89e13d1](89e13d1))
* missing deinits in loadOtherState
([#459](#459))
([094d278](094d278))
* missing state commits
([#454](#454))
([a432b55](a432b55))
* no-op when syncPubkeys run on a pk cache with shrinking validator set
([#432](#432))
([ed05a99](ed05a99))
* param order in BeaconBlockBody
([#348](#348))
([d8b9c06](d8b9c06))
* pendingConsolidations bindings
([#449](#449))
([b9c497e](b9c497e))
* **pmt,ssz:** harden chunked-leaf and zero-copy tree-view memory safety
([#400](#400))
([de50c53](de50c53))
* populate cache balances during rewards/penalties processing
([#474](#474))
([5bf23dc](5bf23dc))
* re-expose sizes
([#369](#369))
([64b81f3](64b81f3))
* remove `slashValidator` gating on active status
([#448](#448))
([d319a0d](d319a0d))
* **ssz:** drop redundant default-init pass in fixed-list decode
([#468](#468))
([0c757be](0c757be))
* **ssz:** publish child cache entries after lookup
([#565](#565))
([21e78c9](21e78c9))
* state transition binding exports
([#456](#456))
([895982c](895982c))
* **state-transition:** group-check signature sets
([#515](#515))
([42774e9](42774e9)),
closes [#502](#502)
* **state-transition:** isolate epoch step cache mutations
([#535](#535))
([a83741a](a83741a))
* **state-transition:** repair Pool.init call broken by
[#346](https://github.com/ChainSafe/lodestar-z/issues/346)×[#367](https://github.com/ChainSafe/lodestar-z/issues/367)
merge skew ([#394](#394))
([b42944f](b42944f))
* various fixes around config
([#433](#433))
([c4f082c](c4f082c))


### Performance Improvements

* **bindings:** drop TS BLS comparison benches and report benchmarks on
PRs ([#552](#552))
([c909c6f](c909c6f))
* **bls:** add cache-aware signature verifier
([#562](#562))
([063857e](063857e))
* **bls:** bypass worker queue for small batches
([#553](#553))
([3f8a6df](3f8a6df))
* **epoch:** replace AutoHashMap with array lookup in reward/penalty
caches ([#286](#286))
([e4e181b](e4e181b)),
closes [#243](#243)
* **pmt:** chunked-leaf packing for basic lists and container_struct
([#346](#346))
([ba156c4](ba156c4))


### Code Refactoring

* allocate `AsyncAggRandData` in one obj
([#384](#384))
([459750f](459750f))
* **bindings/pubkeys:** simplify allocation strategy for aggregate
([#518](#518))
([b82750f](b82750f))
* **bindings:** rename blst Lifecycle to State
([#516](#516))
([0a9c179](0a9c179))
* **bindings:** use zapi js.io() instead of local io module
([#469](#469))
([2b34cc0](2b34cc0))
* **bindings:** wake only required number of workers
([#383](#383))
([1db57f1](1db57f1))
* **bls:** allocations around VMAS
([#395](#395))
([dfda58c](dfda58c))
* **bls:** clean up bls
([#398](#398))
([e0f3b9b](e0f3b9b))
* **bls:** remove need for tracking results for
verifyMultipleAggregateSignatures
([#389](#389))
([6fe5c3f](6fe5c3f))
* **bls:** remove single-threaded fallback
([#390](#390))
([e057713](e057713))
* **clock:** single public Clock; internalize SlotClock
([#463](#463))
([fbab1fa](fbab1fa))
* make XXXDecisionRoot fns return `js.String`
([#342](#342))
([aef4420](aef4420))
* move shuffle into swap_or_not_shuffle module
([#558](#558))
([e56efb2](e56efb2))
* **pubkeys:** centralize the process-wide cache
([#522](#522))
([dc9669d](dc9669d))


### Miscellaneous Chores

* avoid slow tests in AGENTS.md
([#546](#546))
([c60f2a9](c60f2a9))
* bump zapi to include musl build
([#485](#485))
([0b488cc](0b488cc))
* **ci:** pin github actions with sha hashes
([#507](#507))
([167b8f5](167b8f5))
* deprecate unused blst APIs
([#575](#575))
([7b547fa](7b547fa))
* **deps:** bump zapi v2.1.0 -> v2.2.0
([#376](#376))
([0c240d8](0c240d8))
* **deps:** bump zbuild
([#403](#403))
([e2545de](e2545de))
* **deps:** compile blst with ReleaseFast
([#391](#391))
([753a896](753a896))
* **deps:** update zapi to 3.1.0
([#483](#483))
([f3e5827](f3e5827))
* **deps:** use zapi v2.1.0
([#372](#372))
([88f403a](88f403a))
* disable gemini auto code review
([#382](#382))
([63e42a4](63e42a4)),
closes [#380](#380)
* **docs:** add comments section in AGENTS.md
([#566](#566))
([0c09750](0c09750))
* move state clones out of benchmark run functions
([#324](#324))
([e4035de](e4035de))
* prepare 1.0.0 release
([#576](#576))
([20b657b](20b657b))
* release v0.1.2-rc.3
([#370](#370))
([e4fc551](e4fc551))
* **release:** 0.1.2-rc.2
([#365](#365))
([7046128](7046128))
* **release:** v0.1.2-rc.10
([#477](#477))
([9a4fad5](9a4fad5))
* **release:** v0.1.2-rc.4
([#373](#373))
([09468f1](09468f1))
* **release:** v0.1.2-rc.5
([#374](#374))
([f344efa](f344efa))
* **release:** v0.1.2-rc.6
([#375](#375))
([bdf5b67](bdf5b67))
* **release:** v0.1.2-rc.8
([#401](#401))
([06f91c2](06f91c2))
* **release:** v0.1.2-rc.9
([#404](#404))
([6024800](6024800))
* remove merge transition code
([#359](#359))
([09b175d](09b175d))
* remove stale epoch cache TODOs
([#534](#534))
([27a547a](27a547a))
* rename era shortHistoricalRoot to shortEraRoot
([#473](#473))
([c75a4d3](c75a4d3))
* **scripts:** build bindings with preset
([#434](#434))
([a1b5ef7](a1b5ef7))
* silence debug log when used in release builds
([#486](#486))
([c5377d7](c5377d7))
* support dev workflow
([#364](#364))
([fcb9a78](fcb9a78))
* update gloas types to align with the latest specs
([#431](#431))
([1f065b5](1f065b5))
* update spec test version to v1.7.0-alpha.11
([#451](#451))
([5875660](5875660))
* update spec-test-version: v1.6.0-beta.2 -> v1.7.0-alpha.10
([#441](#441))
([f932b1c](f932b1c))
* update zapi to 4.0.0
([#571](#571))
([de8e3fd](de8e3fd))


### Documentation

* document security threat model
([#557](#557))
([e678b87](e678b87))
* more comprehensive AGENTS.md
([#520](#520))
([c74b386](c74b386))
* **pkix:** document load provenance requirement
([#556](#556))
([37e0aa2](37e0aa2))

---
This PR was generated with [Release
Please](https://github.com/googleapis/release-please). See
[documentation](https://github.com/googleapis/release-please#release-please).

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>
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@GrapeBaBa @wemeetagain