Add Lua 5.5 support and fix Zig 0.16 compatibility #193

kaid · 2026-01-30T06:08:43Z

This PR adds support for the latest Lua 5.5 release and improves Zig 0.16 nightly compatibility(0.16.0-dev.2349+204fa8959).

Lua 5.5 Support

Add Lua 5.5 as a new language target - Full integration with build system and package management
Update lua_newstate signature - Lua 5.5 adds a new misize parameter for minimum stack size; handle with conditional compilation
Add DebugInfo55 structure - New debug interface with private field for internal state
Extend version compatibility - Add .lua55 to all relevant version switches:
- ArithOperator, Event, DebugInfo, dump, equal, gc* functions
- Stream, StreamFn, yieldCont continuation signatures
- openCoro, openUtf8 library loaders
Add Lua 5.5 source files - Include ldo.c, lctype.c, lcorolib.c, lutf8lib.c in build
System library linking - Support lua5.5 system library when using use_system_lua

Zig 0.16 Nightly Compatibility

Fix build/patch.zig entry point - Update from legacy pub fn main() !void to new pub fn main(init: std.process.Init.Minimal) !void signature
Modernize argument parsing - Replace std.process.argsAlloc with iterator-based init.args.iterate() API
Fix pointer cast syntax - Update @ptrCast usage for stricter Zig 0.16 type checking in various FFI calls

LuaJIT Fixes

Fix external unwind on Darwin - Remove the LJ_NO_UNWIND=1 workaround now that the Zig compiler bug (ziglang/zig#30669) has been fixed in master by Andrew

Bit Library Improvements

Note: This is a bit of a hack to resolve immediate symbol errors. LuaJIT's bit library and Lua 5.2's bit32 have behavioral differences (different module names, slightly different APIs). A more elegant solution might be to expose them as separate functions or handle the differences at the API level rather than conflating them in openBit32.

Refactor openBit32 - Use explicit switch statement for clarity:
- Lua 5.2: use luaopen_bit32
- LuaJIT: use luaopen_bit (LuaJIT's bit library)
- Other versions: no-op (they don't have bit32)
Simplify test conditions - Explicitly check for lua52 and luajit instead of excluding multiple versions

Files Changed

build.zig - Update version handling
build.zig.zon - Add Lua 5.5 package reference
build/lua.zig - Add Lua 5.5 build configuration
build/luajit.zig - Remove Darwin unwind workaround, restore external unwind
build/patch.zig - Fix Zig 0.16 pointer cast syntax
src/lib.zig - Add Lua 5.5 compatibility, fix error messages and pointer casts, improve bit library handling
src/tests.zig - Fix tests for LuaJIT and Zig 0.16 compatibility, simplify bit32 test conditions
readme.md - Update documentation

- Add lua55 dependency to build.zig.zon (lua-5.5.0.tar.gz) - Add lua55 variant to Language enum in build/lua.zig - Add lua55 source files list (same structure as 5.4) - Update build.zig to handle lua55 system library linking API changes for Lua 5.5 compatibility: - Add DebugInfo55 with i32 first_transfer/num_transfer (changed from u16) - Update lua_newstate() to accept third parameter (seed) for 5.5 - Add null buffer check in CWriterFn wrap (Lua 5.5 calls writer with null at end) - Update all version switches to include .lua55 - Fix @ptrCast type inference in openLibs() Test updates: - Add version check for Lua 5.5 (505) - Update resumeThread calls for 5.4/5.5 (requires num_results parameter) - Update userdata tests to handle 5.5 user_values API - Skip dump/load test for 5.5 (format changed) - Update GC, compare, and concat tests for 5.5 behavior All tests pass for lua52, lua53, lua54, and lua55.

- Replace deprecated std.process.argsAlloc with std.process.Init.Minimal - Update main() signature to use std.process.Init.Minimal parameter - Use init.args.iterate() instead of argsAlloc for command line parsing This fixes the build for Lua 5.1 which uses the patch tool to apply CVE-2014-5461 security fix to ldo.c.

Remove the separate code path for Lua 5.5 in the compare test since the equal() and lessThan() functions now work correctly for all versions. This reduces code duplication and makes the test more maintainable.

The root cause was that LuaJIT was unconditionally compiled with external unwind mode (LUAJIT_UNWIND_EXTERNAL), which requires all frames in the call chain to have proper unwind info. When external unwind fails to propagate (err_raise_ext returns), LuaJIT calls panic and exits. Changes: - Remove LUAJIT_UNWIND_EXTERNAL macro and unwind library linking from build/luajit.zig to use LuaJIT's default internal error handling - Fix registerFns error message to use consistent format for all Lua versions - Add LuaJIT to the exclusion list for openBit32 (LuaJIT doesn't have bit32) - Fix pointer cast order in userdata dtor test (@ptrCast(@alignCast) for Zig 0.16 compatibility) All tests now pass.

Remove the LJ_NO_UNWIND=1 workaround for Darwin now that the Zig compiler bug (https://codeberg.org/ziglang/zig/issues/30669) has been fixed by Andrew Kelley in Zig master: https://codeberg.org/ziglang/zig/commit/63f345a75afdf4f956b136c06776f109f5c567af The bug caused stack check to be incorrectly enabled for external unwind, which made err_raise_ext fail and return instead of properly unwinding.

Refactor openBit32 to use explicit switch statement for clarity: - Lua 5.2: use luaopen_bit32 - LuaJIT: use luaopen_bit (LuaJIT's bit library) - Other versions: no-op (they don't have bit32) Also simplify the test condition to explicitly check for lua52 and luajit instead of excluding multiple versions.

Previously removed the LUA_QS branch in registerFns to work around a c-translate error on Zig nightly. After investigating, this is caused by an upstream bug in Zig's translate-c: https://codeberg.org/ziglang/translate-c/issues/282 The bug affects LUA_QL macro parsing, which breaks LUA_QS (as it expands to LUA_QL). Since this is a confirmed upstream issue and the makefile already disables lua51/luajit tests on nightly due to the same bug, restore the original LUA_QS branch for non-Luau languages. Changes: - Restore LUA_QS usage for lua51-lua54 and luajit in registerFns - Add lua55 test target to test_zig_nightly and test_zig_stable

- Remove skip for Lua 5.5 dump test - it works correctly - Fix closeThread call: pass null instead of lua as "from" parameter When L==from, Lua 5.5 treats this as "thread closing itself" which only works inside a resume. Pass null to reset thread normally. See: https://www.lua.org/manual/5.5/manual.html#lua_closethread

The yielding test has an early return for non-5.3/5.4/5.5 versions, so the else block handling Lua 5.1/LuaJIT was unreachable code. - Change "else if (lua52 or lua53)" to "else" since only 5.3 remains - Remove dead code for 5.1/LuaJIT that could never execute

- gc test: include lua55 in gcSetGenerational check - userdata test: include lua55 in setUserValue/getUserValue check - resuming test: remove lua54 skip, refactor to use switch for clarity

Include lua55 in the upvalueId error test case (same behavior as lua54).

robbielyman

Thanks very much! I'm going to go ahead and make the openBit change I suggested.

robbielyman · 2026-01-30T20:17:31Z

src/lib.zig

-        lua.requireF(c.LUA_BITLIBNAME, c.luaopen_bit32, true);
-        if (lang == .lua52 or lang == .lua53 or lang == .lua54) lua.pop(1);
+        switch (lang) {
+            .lua52 => lua.requireF(c.LUA_BITLIBNAME, c.luaopen_bit32, true),


Since the library is available in Lua 5.3, probably we should require it if the user asks for it. Maybe the openBit32 function should instead be named openBit and use the indicated functions for lua 5.2, 5.3 and luajit, and otherwise be a compile error?

kaid added 11 commits January 29, 2026 16:47

Simplify compare test by removing Lua 5.5 special case

603c1bc

Remove the separate code path for Lua 5.5 in the compare test since the equal() and lessThan() functions now work correctly for all versions. This reduces code duplication and makes the test more maintainable.

fix(tests): add Lua 5.5 support to gc, userdata, and resuming tests

d9d32e8

- gc test: include lua55 in gcSetGenerational check - userdata test: include lua55 in setUserValue/getUserValue check - resuming test: remove lua54 skip, refactor to use switch for clarity

fix(tests): add Lua 5.5 support to upvalueId test

70bd3c6

Include lua55 in the upvalueId error test case (same behavior as lua54).

robbielyman approved these changes Jan 30, 2026

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Add Lua 5.5 support and fix Zig 0.16 compatibility #193

Add Lua 5.5 support and fix Zig 0.16 compatibility #193

kaid commented Jan 30, 2026 •

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Add Lua 5.5 support and fix Zig 0.16 compatibility #193

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kaid commented Jan 30, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Lua 5.5 Support

Zig 0.16 Nightly Compatibility

LuaJIT Fixes

Bit Library Improvements

Files Changed

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kaid commented Jan 30, 2026 •

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