[Freeswitch-dev] [PATCH] Fixed loop unrolling in dialplan configuration

[Travis Cross]

Brian West wrote:
> The same would apply to the call_debug variable too but it works  
> without $$ in the config as is..... And I'm pretty sure they work in  
> either case but you're right it shouldn't have to eval it every time.

I did wonder if there might be some super special magic going on there....

I took a look in switch_xml.c and switch_core.c; now I understand. 
<X-pre-process cmd="set" data="foo=bar"/> does more than operate 
exclusively in the preprocessor, as I intuitively would have expected. 
Instead, it sets foo as a global runtime variable, which is then used by 
the preprocessor during expansion.

When we lookup a channel variable in switch_channel.c, upon finding that 
there is no channel variable by the requested name, we fall back to 
using a global runtime variable by the same name, if one exists.

Cheers,

-- Travis