From: Simen Edvardsen <toalett@...>
Date: 2017-08-22T14:45:48+02:00
Subject: [ruby-core:82448] Exposing rb_iseq_load as a ruby method?

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RubyVM::InstructionSequence is great, it's great that you can compile code
and disassemble. But for my current project (which is currently a toy, but
this may have other useful applications), what I'd really like is to feed
an instruction sequence constructed in Ruby into the iseq assembler. On the
C level, such a function exists and it works, namely, rb_iseq_load, but
it's not exposed on the Ruby level. Other people apparently found this
function useful too, because I found the following snippet online to
dynamically load it:

require "fiddle"
class RubyVM::InstructionSequence
  # Retrieve Ruby Core's C-ext `iseq_load' function address
  # I had to modify this line for my system
  load_fn_addr  =
Fiddle::Handle.new("x64-msvcrt-ruby240.dll")['rb_iseq_load']
  # Retrieve `iseq_load' C function representation
  load_fn       = Fiddle::Function.new(load_fn_addr,
                                       [Fiddle::TYPE_VOIDP] * 3,
                                       Fiddle::TYPE_VOIDP)

  # Make `iseq_load' accessible as `load' class method
  define_singleton_method(:load) do |data, parent = nil, opt = nil|
    load_fn.call(Fiddle.dlwrap(data), parent, opt).to_value
  end
end

The original hack was written for Linux, I think, so I had to manually find
the right DLL for my system and swap it in there. But it works, kinda, in a
hacky way.

Would you ever consider exposing rb_iseq_load as a singleton method of
RubyVM::InstructionSequence? The function already performs quite a few
checks on the validity of the input, and there is already an unsafe way to
load ISeqs via ::from_binary. And that would make it easier to do
interesting things with Ruby codegen.

-- 
- Simen

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<div dir=3D"ltr">RubyVM::InstructionSequence is great, it&#39;s great that =
you can compile code and disassemble. But for my current project (which is =
currently a toy, but this may have other useful applications), what I&#39;d=
 really like is to feed an instruction sequence constructed in Ruby into th=
e iseq assembler. On the C level, such a function exists and it works, name=
ly, rb_iseq_load, but it&#39;s not exposed on the Ruby level. Other people =
apparently found this function useful too, because I found the following sn=
ippet online to dynamically load it:<div><br></div><div>require &quot;fiddl=
e&quot;</div><div><div>class RubyVM::InstructionSequence</div><div>=C2=A0 #=
 Retrieve Ruby Core&#39;s C-ext `iseq_load&#39; function address</div><div>=
=C2=A0 # I had to modify this line for my system</div><div>=C2=A0 load_fn_a=
ddr =C2=A0=3D Fiddle::Handle.new(&quot;x64-msvcrt-ruby240.dll&quot;)[&#39;r=
b_iseq_load&#39;]</div><div>=C2=A0 # Retrieve `iseq_load&#39; C function re=
presentation</div><div>=C2=A0 load_fn =C2=A0 =C2=A0 =C2=A0 =3D Fiddle::Func=
tion.new(load_fn_addr,</div><div>=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0[Fiddle::TYPE_VOIDP] * 3,</div><div>=C2=A0 =C2=A0 =
=C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=
=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0Fiddle::TYPE_VOIDP)</di=
v><div><br></div><div>=C2=A0 # Make `iseq_load&#39; accessible as `load&#39=
; class method</div><div>=C2=A0 define_singleton_method(:load) do |data, pa=
rent =3D nil, opt =3D nil|</div><div>=C2=A0 =C2=A0 load_fn.call(Fiddle.dlwr=
ap(data), parent, opt).to_value</div><div>=C2=A0 end</div><div>end</div><di=
v><br></div><div>The original hack was written for Linux, I think, so I had=
 to manually find the right DLL for my system and swap it in there. But it =
works, kinda, in a hacky way.</div><div><br></div><div>Would you ever consi=
der exposing rb_iseq_load as a singleton method of RubyVM::InstructionSeque=
nce? The function already performs quite a few checks on the validity of th=
e input, and there is already an unsafe way to load ISeqs via ::from_binary=
. And that would make it easier to do interesting things with Ruby codegen.=
</div><div><br></div>-- <br><div class=3D"gmail_signature">- Simen</div>
</div></div>

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