LanguagesCEvidence
cp-wide-bool-flags — measured, still hint
Status
hint. Wall-clock JSONL: cp-wide-bool-flags.jsonl. Not corpus-triaged. The 2026-10-22 corpus verdict does not cover this slug.
Measurement
Copy of 1000000 records. The wide struct is four ints (16 bytes in this build). The packed struct is four unsigned char bit-fields (1 byte in this build). This is a bandwidth microbench of those two layouts, not a claim about every ABI.
| role | case | median_ms | ops | ratio |
|---|---|---|---|---|
| after | copy_uchar_bitfields | 0.067000 | 1000000 | 1 |
| before | copy_four_ints | 1.277000 | 1000000 | 19.060 |
The microbench shows a cost for this one shape. Default stays hint until the shape is corpus-triaged. This ratio is not a general speedup.
Unblock
Do not set the default to error from this file alone. A changing input, a cold path, or another ABI can erase the difference. Corpus triage is still required before any default change.