SamandClaude Fable 5.1
c775181933
- the cooldown pie, the GCD sweep, minimap pings and the map arrow draw again after a logout, login or /reload; they went blank until a restart, which read as OmniCC killing the cooldowns (2113) - an addon's own font on a button label keeps its face, size and outline instead of being undone every frame, MikScrollingBattleText's reported look (2112) - an empty label reads as nothing rather than an empty string, so Cartographer's map label keeps its colour; a slider thumb with no authored size takes its art's own size, so Dewdrop's Look'n'Feel slider moves (2109, 2110) - Bagnon's saved bag list comes back in the order it was written, so the keyring stops jumping to the front after a restart; hovering a Bagnon bag costs a third of what it did (2111, 2114) Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
105 lines
7.6 KiB
Markdown
105 lines
7.6 KiB
Markdown
# benilla's `lua-src` fork — what differs from upstream, and how to check
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Upstream: [`mlua-rs/lua-src-rs`](https://github.com/mlua-rs/lua-src-rs), MIT, version `550.0.0` —
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the version mlua 0.11 resolves to. Wired in through `[patch.crates-io]` in the workspace root.
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## Why a fork exists at all
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**benilla's Lua has to accept exactly the grammar the 1.12.1 client's Lua accepts — no more and no
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less.** Every hunk below is that one rule: three restore 5.0 constructs 5.1 deleted, three delete
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5.1 constructs 5.0 never had. A grammar difference in either direction is invisible to every
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instrument we own until an addon trips over it, and the corpus *asks about* the difference
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directly (decisions 1208, 2101).
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The 1.12 addon corpus is Lua **5.0** code. It uses the iterator-less generic-for:
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```lua
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for k, v in someTable do ... end -- no pairs(), no iterator function
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```
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**183 of 218 corpus addons are reached by it** (118 carry it, 65 inherit it through a declared
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dependency), across 1,163 sites. On stock Lua 5.1 it raises `attempt to call a table value`, and it
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is the **first session-start error for 60 of 218 addons — three quarters of everything that breaks
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once the client is actually running**, eleven times the next cause.
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Lua 5.1 removed it at the **opcode** level, which is why no layer above the VM can reach it. Every
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other dialect gap this project has closed was reachable from inside Lua — `table.setn` is a library
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function, `bit` is a library, `print` is a global (decisions 1194, 1196). This one is not:
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- a `__call` metamethod would work, but the tables are the addon's own and Lua 5.1 has no
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per-*type* default metatable for tables;
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- rewriting the chunk source means parsing Lua with a regex to tell `in t do` from `in pairs(t) do`,
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and getting that wrong changes behaviour silently;
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- there is no `lua50` backend — `lua-src` ships 5.1 through 5.5 and every one of them removed it.
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## What is NOT being done
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**benilla is not adopting Lua 5.0.** We stay on 5.1.5 and restore the behaviour of a single opcode
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that Lua itself shipped and labelled `/* for compatibility only */`. Every other 5.1 fix, and the
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whole of mlua's surface, stay exactly as upstream. That is a far smaller commitment than a version
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downgrade, and it is the entire reason this is a one-hunk fork rather than a vendored 5.0.
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## The delta, and the command that proves it
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**Current state: seven hunks, in three files.** `src/lib.rs` additionally differs by having Lua
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5.2/5.3/5.4/5.5 stripped from the `Version` enum (with their source trees deleted) — benilla builds
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5.1 and only 5.1, and a fork that still *offered* the other four would answer a request for one with
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a missing directory at build time instead of a compile error.
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**Four hunks restore what 5.1 changed or removed:**
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| file | hunk | why | record |
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|---|---|---|---|
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| `lvm.c` | 5.0's `OP_TFORPREP` table→`next` substitution, folded into the top of `OP_TFORLOOP` | `for k, v in someTable do` raised "attempt to call a table value"; it was the first session-start error for **60** corpus addons | 1215 |
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| `luaconf.h` | `LUA_COMPAT_LSTR` `1` → `2` | 5.1 kept 5.0's nesting machinery and put an advisory error in front of it; two corpus addons died on "nesting of `[[...]]` is deprecated" | — |
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| `lparser.c` | 5.0's compat-semicolon skip restored at the top of `constructor()`'s field loop — 5.0's own line, verbatim, comment included | one extra `;` after a field separator inside a table constructor (`Back_Title = AL["Factions"];;`, ×20 in AtlasLoot's `ButtonRegistry.lua`) parses on the client and died here with "unexpected symbol near `;`"; statement-level `;;` stays rejected by both dialects | 1315 |
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| `lparser.c` | `recfield`'s `cc->nh++` moved back INSIDE its `TK_NAME` arm — 5.0's own placement | a `[expr] = value` constructor field must credit **neither** `OP_NEWTABLE` size hint, so the table is born on the dummy node, the first store rehashes, and the dense integer keys land in an ARRAY part that `next` walks ascending. 5.1 pre-sizes a node vector instead and leaves them in the hash, where `next` is slot order — so every list in every saved-variables file came back scrambled (Bagnon's keyring drew first) | 2111 |
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**Three delete what 5.1 added** — all in `lparser.c`, all byte-read out of the client's own parser
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(`simpleexp 0x6fd240`, `getunopr 0x6fe0a0`, `getbinopr 0x6fe0c0`), all landing on 5.0's own
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`unexpected symbol` at `prefixexp 0x6fde40`:
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| hunk | why | record |
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|---|---|---|
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| `simpleexp`'s `case TK_DOTS` deleted — `...` is no longer an expression | the Ace2 corpus **asks** which interpreter it is on by compiling `return function(...) return ... end`; 170 `loadstring` sites in the 219-addon corpus are that question and 92 library files gate on it. Answering `true` put Cartographer on its client-2.0 branch, hooking `CloseSpecialWindows` — a name 1.12 does not have. Also restores 5.0's rule that **every** vararg function gets its `arg` table | 1208, 2101 |
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| `getunopr`'s `case '#'` deleted — no length operator | the client's `getunopr` tests exactly two tokens (`-`, `not`) and its `OPR_NOUNOPR` is **2**: a three-member enum, 5.0's. 5.0 asks a table with `table.getn` and a string with `string.len` | 2101 |
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| `getbinopr`'s `case '%'` deleted — no modulo operator | the client's `getbinopr` switch is based at `'*'` (0x2A), so `%` (0x25) is below its range and reaches `OPR_NOBINOPR` = **14**: a fifteen-member `BinOpr`, 5.0's. 5.0 spells it `math.mod` | 2101 |
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The ordering was deliberate and it held: the fork landed **inert**, byte-identical to upstream, so
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the build pipeline was proven transparent *before* any behavioural payload went into it — and when
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the suite then moved, the patch was the only thing that could have moved it. Every hunk is measured
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against the corpus rather than argued: the long-string one alone took loaded 134 → 139 and
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survivors 99 → 104.
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**The deletions are safe because nothing the reference runs uses those constructs, and that was
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scanned rather than assumed** (2101 §4): a comment/string-stripping scan of the extracted 1.12
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FrameXML (177 files), GlueXML, Blizzard's own addons and the director's installed AddOns folder
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finds **zero** sites of all three. Our own engine Lua did use them and was rewritten into the 5.0
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spellings; the rule now is that no chunk of ours may use a construct the client's parser rejects.
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To verify the Lua sources against upstream at any time:
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```sh
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# 550.0.0 is the pinned version; adjust the path if cargo's registry hash differs.
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diff -r third_party/lua-src/lua-5.1.5 \
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~/.cargo/registry/src/*/lua-src-550.0.0/lua-5.1.5
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```
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That must print **exactly** the seven hunks in the tables above and nothing else. If it ever prints
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more, something crept in.
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## Status of the payload
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**Landed.** The reverse-engineering answer this was deliberately blocked on came back from
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`wow-5875-re` (`system/ui/scratch/lua-generic-for.md`) and is what the `lvm.c` comment cites, detail
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by detail: a **bare type-tag** test that never consults a metatable (so a table carrying `__call`
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still gets `next`), the **global** `next` read raw and fetched fresh at every loop entry (so an addon
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assigning `next = myfn` changes every later generic-for in the session), and userdata *not*
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substituted.
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Waiting was the right call twice over. Checking stock 5.0 first corrected two assumptions the
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project had already written down — the substitution happens in `OP_TFORPREP`, an opcode 5.1 deleted,
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*not* in `OP_TFORLOOP`; and the test is a bare `ttistable` with no `__call` check. Stock 5.0 was
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corroboration, never the authority: the client links 5.0 but may be modified, and only the byte-read
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of the client settles what it actually does.
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