Re: Lua Compile/one time Load?

[Sean Conner <sean@...>]

It was thus said that the Great Iurii Belobeev once stated:
> On Wed, 18 Oct 2023 at 21:36, Keith Cancel <admin@keith.pro> wrote:
> 
> > I was looking at the source code trying to see if there was a way
> > maybe to achieve something similar to lua_load(), but at compile time.
> > Basically, I want to bunch a shared code to only occupy the memory
> > once instead of creating copies for each new lua VM instance. I
> > basically just want that code in ROM that can be executed by each new
> > instance without having to copy it over first.
> 
> you can precompile lua text source by calling lua_dump and safely put it
> into shared memory. it will produce binary chunk which then can be
> converted to lua function by calling lua_load on it. you cannot reuse
> result of lua_load since global table _G is pushed as upvalue to the
> resulting function, i.e. is not reusable.

  I don't think that will acccomplish what Keith asked for.  I think Keith
is asking, can I, once Lua code is compiled, share the resulting VM code
among different Lua states in the same process?  Yes, you can use lua_dump()
and store the code into shared memory (either at run time, or at compile
time [1]), but when calling lua_load() memory is allocated to store the code
into the currently running VM.

  An approach would be to get pointers to the underlying structures in the
initial VM, and then somehow make them available to another VM, but you
would have to ensure the structures are immune to garbage collection, else
bad things could happen.  That might be good for a hack, but not for
production code.

  -spc

[1]	As I outlined here: https://boston.conman.org/2023/03/22.1