WeirdUtils/experiments/wp24b-gc/README.md

WeirdPerformance 2.4-B1 — GC Safe Sweep ABI-fixed test

Strict A/B experiment for WoW 1.12.1 build 5875.

Baseline

Keep the validated 2.4-A binary unchanged:

• weirdperformance.dll
• SHA-256: d35168ae06c19087ef9b7c68918a054640396dfbfcef0664e18e9372284b5eef

B1 variant

Add:

• weirdperformance_gc24b1.dll

The companion changes only Lua GC behavior. It does not replace or rebuild the validated 2.4-A DLL.

The first 2.4-B build is invalid and must not be used. It was built with an i386 Windows fastcall ABI mismatch and crashed at startup in WoW's native lua_gc_remove_objects. B1 is built with a pinned Zig 0.17 development toolchain and is binary-disassembly checked for the expected register ABI before distribution.

The implementation is based on the historical pre-generational incremental sweep: WoW keeps its native mark, userdata/string sweep, memory shrink and finalizers. Only the main rootgc sweep is split into 50,000-object chunks.

Safety scope

• hooks only luaC_collectgarbage and lua_close;
• no overlap with the lifecycle hooks referenced by the validated 2.4-A binary;
• any fragmented sweep is reconnected before native lua_close destroys the Lua state;
• GC calls made from inside lua_close stay native;
• the birth-mark byte is ownership checked and restored only while still owned;
• a changed Lua global_State forces native fallback rather than reconnecting stale pointers;
• hook installation is transactional;
• no generational age bitmap, no write barriers, no GC tuning, no profiling/RDTSC.

Installation for the test

Keep both DLLs next to WoW and list both in dlls.txt:

weirdperformance.dll
weirdperformance_gc24b1.dll

Delete the old weirdperformance_gc24b.dll if it is still present.

Removing weirdperformance_gc24b1.dll returns you exactly to the validated 2.4-A baseline.