not accessible variable under @defined predicate

[Wenji Huang]

Hi,

In FC13, I got the following error message,

$stap -e 'probe process("stap").mark("pass2__end") 
{print(@defined($arg1)? $arg1:$nosuchvar)}'
semantic error: unable to find local 'nosuchvar' near pc 0x805260a in 
<unknown>(main.cxx) (alternatives: arg1): identifier '$nosuchvar' at 
<input>:1:72
         source: probe process("stap").mark("pass2__end") 
{print(@defined($arg1)? $arg1:$nosuchvar)}
 

Stap means there is no $arg1 and so it tried $nosuchvar for the probe 
point, but $arg1 is there and even provided as alternative. In fact, the 
$arg1 isn't accessible.

$ stap -p2 -e 'probe process("stap").mark("pass2__end"){print($arg1)}'
semantic error: not accessible at this address (0x805260a): identifier 
'$arg1' at <input>:1:48
         source: probe process("stap").mark("pass2__end"){print($arg1)}

The current hint message will confuse the users. My suggestion is to 
keep the "not accessible" message or @defined predicate will return true 
once the target symbol exists, even not accessible.

Regards,
Wenji