[syslinux] constants and line continuation

[Warren Block]

On Tue, 13 Jul 2010, Jim Cromie wrote:

> is this a good application for lua ?
>
> if lua is 'ready' when the config is requested and downloaded,
> the file could contain lua code that is run to produce all the
> menus, kernels, append-lines etc.

This got me thinking about lua as a preprocessor.  Load a lua module 
with UI, have it preprocess a menu file and then hand back off to a real 
UI module...

And then it occurred to me that for simple constants and line 
continuations, run-time evaluation isn't needed:

   #define HTTPHOST http://192.168.1.1

   ui vesamenu.c32

   label clonezilla
     menu label Clonezilla
     kernel images/clonezilla/vmlinuz
     append boot=live union=aufs noswap vga=788 \
     ocs_lang="en_US.UTF-8" \
     ocs_live_keymap="/usr/share/keymaps/i386/qwerty/us.kmap.gz" \
     fetch=HTTPHOST/images/clonezilla/filesystem.squashfs

Of course you then have to "compile" your menu files before use, but 
it's not bad:

% cpp -traditional-cpp menu.src default     # for pxelinux.0

That "-traditional-cpp" is so the // in URLs aren't seen as comments.