[Asterisk-Dev] DIAL_PRESERVE_CALLERID logic (Dial() option 'o')

[Thomas Andrews]

Hi,

Can someone please explain the logic behind DIAL_PRESERVE_CALLERID in
other words the 'o' flag used in Dial()

I can't think of any situation where you would *not* want the 'o' flag.

I was hunting down why my cid.cid_num kept on getting clobbered, and I
discovered that someone had already solved my problem by introducing the
DIAL_PRESERVE_CALLERID flag. The flag prevents cid_num from getting
over-written with ${EXTEN}.

What I actually want to know is why anyone would *ever* want cid_num
over-written with ${EXTEN} ? I can think of a few exceptional cases
where this might no be harmful, but the situation is particularly bad in
a (simplified) case like this:

exten => s,1,Goto(SOMELABEL,1)
exten => SOMELABEL,1,Dial(Zap/1)

Now in this case ${EXTEN} is "SOMELABEL" which is hardly suitable for
cid_num.
 
Many Thanks,
Thomas