[ns] segmentation fault when using Exponential distribution

[Z Sun <esrub@eng.warwick.ac.uk>]

Hi, 

Could anybody tell me why I got segmentation fault when I run the
following source code.

***********************************
set udp_(0) [new Agent/UDP]
$ns_ attach-agent $node_(1) $udp_(0)
set null_(0) [new Agent/Null]
$ns_ attach-agent $node_(0) $null_(0)
$ns_ connect $udp_(0) $null_(0)
set cbr_(0) [new Application/Traffic/Exponential]
#set cbr_(0) [new Application/Traffic/CBR]
$cbr_(0) set packetSize_ 512
$cbr_(0) set rate_ 1M
$cbr_(0) set burst_time_ 1s
$cbr_(0) set idle_time_ 1.35s
$cbr_(0) attach-agent $udp_(0)
$ns_ at 0.0 "$cbr_(0) start"
*******************************************

Everything is fine when I do set cbr_(0) [new Application/Traffic/CBR]

thanks,

Ziran