Re: Subject: [ANN] Lua 5.5.1 (rc1) now available

On 2026-07-15 22:53, Luiz Henrique de Figueiredo wrote:
> Lua 5.5.1 (rc1) is now available for testing at
> https://www.lua.org/work/lua-5.5.1-rc1.tar.gz

Congratulations with release! (I still admire your admittance of bugs.)

Lua 5.5.1 (as many previous versions) sometimes produces bytecode
with unreachable instructions. (At least I don't understand
how they can be reached.)

For example "local f =3D function() end; return f;":

 =C2=A0 > $ echo 'local f =3D function() end; return f;' | luac -p -l -s -
 =C2=A0 >
 =C2=A0 > main <stdin:0,0> (4 instructions at 0x5626f1974b30)
 =C2=A0 > 0+ params, 2 slots, 1 upvalue, 1 local, 0 constants, 1 function
 =C2=A0 >=C2=A0 =C2=A01 [1] VARARGPREP=C2=A0 0
 =C2=A0 >=C2=A0 =C2=A02 [1] CLOSURE=C2=A0 =C2=A00 0 ; 0x5626f1974e20
 =C2=A0 >=C2=A0 =C2=A03 [1] RETURN=C2=A0 =C2=A0 0 2 1 ; 1 out
 =C2=A0 >=C2=A0 =C2=A04 [1] RETURN=C2=A0 =C2=A0 1 1 1 ; 0 out
 =C2=A0 >
 =C2=A0 > function <stdin:1,1> (1 instruction at 0x5626f1974e20)
 =C2=A0 > 0 params, 2 slots, 0 upvalues, 0 locals, 0 constants, 0 functions
 =C2=A0 >=C2=A0 =C2=A01 [1] RETURN0
 =C2=A0 >

"RETURN 1 1 1" looks unreachable and dead code.

(I understand that's code generation quirk and code generation
is not simple thing.)

I hope dead bytecode will be reduced in future Lua versions.

-- Martin


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