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GCCJIT Module ​

src/lua_gccjit.cpp registers package.preload["gccjit"] and exposes libgccjit to Lua/Fennel.

This is a thin wrapper over the C API with explicit release/drop behavior.

Availability ​

  • Linux only.
  • Build requires pkg-config --cflags --libs libgccjit.

Factory API ​

fennel
(local gccjit (require :gccjit))

(local ctxt (gccjit.Context))
(local timer (gccjit.Timer))

Core Objects ​

  • ContextRef (:drop/:release)
  • ResultRef (:drop/:release)
  • TimerRef (:drop/:release)
  • BorrowedTimerRef (returned by ContextRef:get-timer; no release/drop)
  • Type, Field, Struct, Function, Block, RValue, LValue, Param, Case, ExtendedAsm, Object, Location

Enum Tables ​

  • gccjit.StrOption
  • gccjit.IntOption
  • gccjit.BoolOption
  • gccjit.OutputKind
  • gccjit.Types
  • gccjit.FunctionKind
  • gccjit.GlobalKind
  • gccjit.UnaryOp
  • gccjit.BinaryOp
  • gccjit.Comparison

Minimal Example ​

fennel
(local gccjit (require :gccjit))

(local ctxt (gccjit.Context))
(local int-type (ctxt:get-type (. gccjit.Types "int")))
(local a (ctxt:new-param nil int-type "a"))
(local b (ctxt:new-param nil int-type "b"))

(local fn
  (ctxt:new-function nil
                     (. gccjit.FunctionKind "exported")
                     int-type
                     "add"
                     [a b]
                     false))

(local entry (fn:new-block "entry"))
(local sum (ctxt:new-binary-op nil
                               (. gccjit.BinaryOp "plus")
                               int-type
                               (a:as-rvalue)
                               (b:as-rvalue)))
(entry:end-with-return nil sum)

(local result (ctxt:compile))
(print (result:call-i32 "add" [2 3])) ; 5

(result:drop)
(ctxt:drop)

Function Invocation from Fennel ​

ResultRef provides callable helpers:

  • call-i32(name [, args])
  • call-i64(name [, args])
  • call-double(name [, args])
  • call-void(name [, args])
  • call-word(name [, args])
  • call-pointer(name [, args])
  • call-void-word(name [, args])

These are intended for direct runtime use in Fennel tests/tools. C++ integrations can use get-code-address/get-global-address.

Current helper limits:

  • call-i32: up to 6 integer args
  • call-i64: up to 4 integer args
  • call-double: up to 8 double args
  • call-void: up to 2 integer args
  • call-word/call-pointer: up to 8 machine-word args (uintptr_t ABI path)
  • call-void-word: up to 4 machine-word args

Use call-word/call-pointer for generic integer/pointer signatures from Fennel. For mixed floating-point + integer/pointer signatures, use get-code-address from C++.

Logfile Lifecycle ​

  • ContextRef:set-logfile(path) replaces any prior logfile handle.
  • ContextRef:clear-logfile() detaches and closes the logfile.

Tests ​

  • assets/lua/tests/test-gccjit.fnl
  • Included in slow suite: assets/lua/tests/slow.fnl
  • C++ binding smoke test: tests/test_lua_gccjit_binding.cpp

Note: deeper stress cases around child-context chaining/vector-heavy IR are kept out of default CI runs on this distro due an upstream GCC 12 libgccjit ICE. Set GCCJIT_STRESS=1 to enable those extra tests explicitly.