adding statements in alias definition as epilogue

[Li Guanglei]

Currently the statement block that follows an alias definition is 
implicitly added as a prologue to any probe that refers to the alias. 
But it seems to me that only allowing adding those statements 
contained in an alias definition as a prologue makes me to lose some 
controls over them.

For example, I have a tapsets:

probe addevent.tskdispatch.cpuidle
         = kernel.inline("idle_balance")
{
         log_cpuidle_tracedata(HOOKID_TASK_CPUIDLE, backtrace)
}

What I want is to let user specify whether to log backtrace in his 
scripts, like the following:

stap -e "probe addevent.tskdispatch.cpuidle { backtrace=1 } -I 
LKET_TAPSETS

But unfortunately, it won't work because "backtrace=1" is added after 
"log_cpuidle_tracedata(HOOKID_TASK_CPUIDLE, backtrace)". So how about 
providing a way to specify whether the statements in a alias 
definition could be added as prologue or epilogue to any probe that 
refers to that alias?