Can't access argument of process marker

[Wenji Huang <wenji.huang@oracle.com>]

Hi,

I got the failure when running test semok/thirtysix.stp. The error
is triggered by the following script,

$ stap -e 'probe process("stap").mark("*")? { 
println(@defined($arg1)?$arg1:$nosuchvar) }'
semantic error: invalid argument number: identifier '$nosuchvar' at 
<input>:1:66
         source: probe process("stap").mark("*")? { 
println(@defined($arg1)?$arg1:$nosuchvar) }
 
           ^
Pass 2: analysis failed.  Try again with another '--vp 01' option.

It seems arguments of marker aren't accessible. Moreover, I think
it's not very accurate to complain "invalid argument number". In fact, 
the variable doesn't follow the naming rule, it's better to make
a little modification and give some hints like $argN.


Regards,
Wenji