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Subject: Re: [geda-user] FOSDEM
From: Peter Clifton <pcjc2 AT cam DOT ac DOT uk>
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Date: Sat, 07 Feb 2015 17:13:42 +0000
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On Sat, 2015-02-07 at 11:20 -0500, Jason White wrote:

> In the Lua virtual machine I added a protected mode for reading "data"
> files where I disabled all instructions not related to pushing
> constants to the stack.
> 
> What does this mean? In this mode, a Lua file is not an executable
> script; there are no functions, no function calls, no if statements or
> for loops. The only thing that is allowed is the definition of
> variables which are easily read out by a program. (Look at the example
> program I linked to, it implements all this)


Sadly I don't have time to get to far into this, and whilst probably
important for the future - is not something I've got any time to
contribute to.

I'm currently taking time out from the PCB+GL and 3D stuff I want to get
merged in order to fix some polygon bugs that are raising their ugly
heads. (Long-standing bugs, but perhaps more commonly seen now due to
the nm core coordinate switch).

Regarding the language..

Sand-boxing for security is great, but doesn't address the (IMO)
undesirability of a turing complete config / data file.

By the time you've pared down the language to the point it sounds you
have, IE. a non-turing complete "language" used for its input file
parser.

It hardly seems that we would be "using" the underlying language at all;
you are merely borrowing its syntax for variable assignment, and using
its interpreter to avoid writing your own file parser.

A similar thing (I think) would be S-Expressions, which most scheme /
lisp environments would be able to read very naturally, and without
execution. There is also JSON / JSONP and Javascript.


Peter

-- 
Peter Clifton <peter DOT clifton AT clifton-electronics DOT co DOT uk>

Clifton Electronics