fix: primitive vec fast-path skip bug + release 0.10.26 by lwshang · Pull Request #720 · dfinity/candid

lwshang · 2026-03-18T00:45:21Z

Summary

Fix decoding failure when a trailing/extra argument is a primitive vector (vec int8/16/32/64, vec nat8/16/32/64, vec float32/64, vec bool)
The fast-path optimization (perf: fast-path exact primitive vector decode #712) skipped setting expect_type/wire_type per element; deserialize_ignored_any then misidentified the element type and corrupted the byte stream
Fix: always set element types before calling seed.deserialize, skipping only the add_cost(3) call in the fast path
Release candid 0.10.26

Test plan

New regression test primitive_vector_is_extra_args in tests/compatibility_vectors.rs covers the exact failure scenario
All existing compatibility_vectors tests continue to pass

🤖 Generated with Claude Code

When decoding a trailing/extra argument that is a primitive vector, `deserialize_ignored_any` relies on `expect_type`/`wire_type` being set to the element type. The fast path introduced in #712 skipped setting these, causing `deserialize_ignored_any` to see the outer `Vec<T>` type and attempt to decode a nested vector instead of a scalar, corrupting the byte stream. Fix: always set `expect_type`/`wire_type` to the element type before calling `seed.deserialize`, and only skip `add_cost(3)` in the fast path. The `primitive_impl!` macro checks `primitive_vec_fast_path` before touching these types, so normal decode performance is unchanged. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

github-actions · 2026-03-18T00:50:17Z

Name	Max Mem (Kb)	Encode	Decode
blob	4_224	4_207_487	2_122_431
btreemap	73_856	531_976_003	13_022_440_615
nns	192	2_021_253	5_661_508 ($\textcolor{green}{-0.03\%}$)
nns_list_proposal	1_216	7_010_160 ($\textcolor{green}{-0.13\%}$)	64_258_407 ($\textcolor{green}{-0.01\%}$)
option_list	64	716_065	21_934_672
text	6_336	4_204_384	7_877_758
variant_list	64	711_213	20_747_140 ($\textcolor{green}{-0.01\%}$)
vec_int16	12_480	8_404_689	553_673_483 ($\textcolor{red}{35.38\%}$)
vec_nat	9_664	67_095_666	844_307_045 ($\textcolor{red}{0.25\%}$)
vec_nat32	24_768	16_793_297	549_479_471 ($\textcolor{red}{35.75\%}$)
vec_nat64	49_344	33_570_495	557_868_339 ($\textcolor{red}{36.41\%}$)

Parser cost: 16_174_059 ($\textcolor{green}{-0.03\%}$)
Extra args: 2_838_386 ($\textcolor{green}{-0.00\%}$)

Click to see raw report

---------------------------------------------------

Benchmark: blob
  total:
    instructions: 6.33 M (no change)
    heap_increase: 66 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 4.21 M (no change)
    heap_increase: 66 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 2.12 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: btreemap
  total:
    instructions: 13.55 B (no change)
    heap_increase: 1154 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 531.98 M (no change)
    heap_increase: 159 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 13.02 B (no change)
    heap_increase: 995 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: extra_args
  total:
    instructions: 2.84 M (-0.00%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: nns
  total:
    instructions: 24.69 M (-0.03%) (change within noise threshold)
    heap_increase: 3 pages (no change)
    stable_memory_increase: 0 pages (no change)

  0. Parsing (scope):
    calls: 1 (no change)
    instructions: 16.17 M (-0.03%) (change within noise threshold)
    heap_increase: 3 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 2.02 M (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 5.66 M (-0.03%) (change within noise threshold)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: nns_list_proposal
  total:
    instructions: 71.27 M (-0.02%) (change within noise threshold)
    heap_increase: 19 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 7.01 M (-0.13%) (change within noise threshold)
    heap_increase: 5 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 64.26 M (-0.01%) (change within noise threshold)
    heap_increase: 14 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: option_list
  total:
    instructions: 22.65 M (no change)
    heap_increase: 1 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 716.07 K (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 21.93 M (no change)
    heap_increase: 1 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: text
  total:
    instructions: 12.08 M (no change)
    heap_increase: 99 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 4.20 M (no change)
    heap_increase: 66 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 7.88 M (no change)
    heap_increase: 33 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: variant_list
  total:
    instructions: 21.46 M (-0.01%) (change within noise threshold)
    heap_increase: 1 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 711.21 K (no change)
    heap_increase: 0 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 20.75 M (-0.01%) (change within noise threshold)
    heap_increase: 1 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: vec_int16
  total:
    instructions: 562.08 M (regressed by 34.67%)
    heap_increase: 195 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 8.40 M (no change)
    heap_increase: 130 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 553.67 M (regressed by 35.38%)
    heap_increase: 65 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: vec_nat
  total:
    instructions: 911.40 M (0.23%) (change within noise threshold)
    heap_increase: 151 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 67.10 M (no change)
    heap_increase: 33 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 844.31 M (0.25%) (change within noise threshold)
    heap_increase: 118 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: vec_nat32
  total:
    instructions: 566.28 M (regressed by 34.32%)
    heap_increase: 387 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 16.79 M (no change)
    heap_increase: 258 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 549.48 M (regressed by 35.75%)
    heap_increase: 129 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Benchmark: vec_nat64
  total:
    instructions: 591.44 M (regressed by 33.65%)
    heap_increase: 771 pages (no change)
    stable_memory_increase: 0 pages (no change)

  1. Encoding (scope):
    calls: 1 (no change)
    instructions: 33.57 M (no change)
    heap_increase: 514 pages (no change)
    stable_memory_increase: 0 pages (no change)

  2. Decoding (scope):
    calls: 1 (no change)
    instructions: 557.87 M (regressed by 36.41%)
    heap_increase: 257 pages (no change)
    stable_memory_increase: 0 pages (no change)

---------------------------------------------------

Summary:
  instructions:
    status:   Regressions detected 🔴
    counts:   [total 12 | regressed 3 | improved 0 | new 0 | unchanged 9]
    change:   [max +148.90M | p75 +37.75M | median 0 | p25 -586 | min -16.14K]
    change %: [max +34.67% | p75 +8.58% | median 0.00% | p25 -0.00% | min -0.03%]

  heap_increase:
    status:   No significant changes 👍
    counts:   [total 12 | regressed 0 | improved 0 | new 0 | unchanged 12]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

  stable_memory_increase:
    status:   No significant changes 👍
    counts:   [total 12 | regressed 0 | improved 0 | new 0 | unchanged 12]
    change:   [max 0 | p75 0 | median 0 | p25 0 | min 0]
    change %: [max 0.00% | p75 0.00% | median 0.00% | p25 0.00% | min 0.00%]

---------------------------------------------------

Only significant changes:
| status | name                   | calls |     ins |  ins Δ% |  HI |  HI Δ% | SMI |  SMI Δ% |
|--------|------------------------|-------|---------|---------|-----|--------|-----|---------|
|   +    | vec_nat64::2. Decoding |     1 | 557.87M | +36.41% | 257 |  0.00% |   0 |   0.00% |
|   +    | vec_nat32::2. Decoding |     1 | 549.48M | +35.75% | 129 |  0.00% |   0 |   0.00% |
|   +    | vec_int16::2. Decoding |     1 | 553.67M | +35.38% |  65 |  0.00% |   0 |   0.00% |
|   +    | vec_int16              |       | 562.08M | +34.67% | 195 |  0.00% |   0 |   0.00% |
|   +    | vec_nat32              |       | 566.28M | +34.32% | 387 |  0.00% |   0 |   0.00% |
|   +    | vec_nat64              |       | 591.44M | +33.65% | 771 |  0.00% |   0 |   0.00% |

ins = instructions, HI = heap_increase, SMI = stable_memory_increase, Δ% = percent change

---------------------------------------------------
Successfully persisted results to canbench_results.yml

lwshang and others added 4 commits March 17, 2026 20:33

chore: update changelog for primitive vec fast-path fix

ca71d3d

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

chore: update changelog for 0.10.26

afea579

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

chore: bump version to 0.10.26

314e563

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lwshang marked this pull request as ready for review March 18, 2026 00:49

lwshang requested a review from a team as a code owner March 18, 2026 00:49

viviveevee approved these changes Mar 18, 2026

View reviewed changes

lwshang merged commit defcf83 into master Mar 18, 2026
11 checks passed

lwshang deleted the lwshang/fix_primitive_vec_fast_path_skip branch March 18, 2026 14:03

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fix: primitive vec fast-path skip bug + release 0.10.26#720

fix: primitive vec fast-path skip bug + release 0.10.26#720
lwshang merged 4 commits intomasterfrom
lwshang/fix_primitive_vec_fast_path_skip

lwshang commented Mar 18, 2026

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lwshang commented Mar 18, 2026

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