oc-nsstring-append-hot — NSString append vs NSMutableString
Status: measured (gnustep)
Claim
GNUstep: stringByAppendingFormat in a loop vs NSMutableString ~569× at N=15000.
How measured
- Harness:
packages/objcperf/examples/bench/evidence_oc.m - Raw lines:
oc-nsstring-append-hot.jsonl
Runtime (this evidence file)
| Field | Value |
|---|---|
| When | 2026-10-22 Asia/Shanghai (JSONL ts is UTC) |
| runtime | gnustep |
Median before (stringByAppending) | ~1236 ms |
Median after (mutable_string) | ~2.172 ms |
| ratio before/after | ~569× |
Lint mapping
objcperf-lint oc-nsstring-append-hot: default stays off.
Limits
- The harness times
stringByAppendingFormat:; the lint matchesstringByAppendingStringonly. - Strong on GNUstep; Apple runtime may differ. Default stays off.