[Bug tapsets/10466] New: stap -L misrepresents variables available to multi-probe aliases

["jistone at redhat dot com" <sourceware-bugzilla at sourceware dot org>]

The listing mode attempts to clean up the output by only printing probe points
once, even if that name is an alias for several probe points underneath. 
However, -L only considers the variables from the first underlying probe point,
which is an issue if the multiple probe points don't have the same available
variables.

Usually the tapset writers try to define the same local variables for each
branch, but the recent addition of dwarf variables to -L exposes the difference
in the raw probe points.

$ stap -L signal.send
signal.send name:string shared:long sig:long task:long sinfo:long
send2queue:long sig_name:string sig_pid:long pid_name:string si_code:string
$sig:int $info:struct siginfo* $t:struct task_struct* $group:int $pending:struct
sigpending* $q:struct sigqueue*

Some of the $vars are only present in one part of signal.send, so they're not
actually usable in a signal.send probe body.

Rather than showing the variables of just one branch, -L should show the
set-intersection of each branch, so that every variable listed is actually useful.

-- 
           Summary: stap -L misrepresents variables available to multi-probe
                    aliases
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: tapsets
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: jistone at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=10466

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