Fw: Lua was Re: Quickstart Build instructions

Russell Haley russ.haley at gmail.com
Tue Apr 10 05:58:20 UTC 2018

On Mon, Apr 9, 2018 at 5:53 PM, Chris Johns <chrisj at rtems.org> wrote:

> On 10/04/2018 10:40, Gedare Bloom wrote:
> > On Mon, Apr 9, 2018 at 4:17 PM, Russell Haley <russ.haley at gmail.com
> > <mailto:russ.haley at gmail.com>> wrote:
> >             I'd like to start with getting other Lua scripts running. My
> goal is
> >             to load a library called penlight that's a few dozens of
> files. Is
> >             there a utility for creating and loading resources? I'll
> also look
> >             at compiling the files using the luac compiler, but that's
> outside
> >             of rtems.
> >
> > No worries. There is evolving support (pretty mature by now) for
> dynamically
> > loading object code, if that is what you mean: the Runtime Loader
> (RTL).  I
> > don't have any experience with it though. Chris Johns is the expert on
> that topic.
> >
> The support is based around the standard calls 'dlopen' etc. You can load
> object files. You do need a symbol table in the kernel and a simple
> makefile
> recipe can be found in the testsuite which works on the sparc simulator:
> https://git.rtems.org/rtems/tree/testsuites/libtests/Makefile.am#n319
>  (search for TEST_dl01 in the Makefile.am if the line has moved)
> Note, the erc32 sim does not have access to a host's file system so you
> will
> need to package the object files into a tar file just as the test does.
Hi Chris, good to hear from you. Yes, the non-filesystem is what I'm trying
to deal with. Lua can run as C or as Lua scripts. The dlopen support is
excellent and I'll look into that when I start loading C. There are many
fine Lua wrappers for some of the best C tools. Since, I'm trying to load
lua scripts, the tar package sounds like what I need to look at first.

Lua scripts can be loaded as a 'string' buffer (char array), or from a
file. Either of those methods can load a text file or a Lua VM binary.
Using binary is apparently faster to load, but must be compiled for the
same architecture. The run speed is the same.

A simple Lua script to load a second module would look like this:

    local my_lib = require('mylib.init')
    local new_val = my_lib.dosomething()

The require() function loads the file from a filesystem based on the
package.path string. On my windows box, it looks like this:

.\?.lua;C:\Program Files (x86)\LuaRocks\lua\?.lua;C:\Program Files
(x86)\LuaRocks\lua\?\init.lua;C:\Program Files
Files (x86)\WinLua\Lua\5.3\bin\?53.dll;

So, the require('mylib.init') would get translated so the '.' becomes the
path separator on the filesystem, and any '?' in the package.path is
replaced with the package name, eventually landing on
C:\Users\russh\scripts\mylib\init.lua. Let's see how that translates to


> Chris
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.rtems.org/pipermail/users/attachments/20180409/4ef17b7d/attachment-0002.html>

More information about the users mailing list