[Bug translator/7071] New: optional $context variables

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

amacleod and others have occasionally asked for the ability for a script to
refer to $vars that may not actually exist at the given probe point for
whatever reason.  The idea would be to let the translator accept such scripts,
substituting a literal '0' and I guess a warning at translate time.

One possibility is to just make this a session-level flag driven by a new 
command line argument.  The effect would be to change tapsets.cxx:4634ish (the
catch semantic-error block in dwrf_var_expanding_copy_visitor) ... or perhaps
translate.cxx's c_unparser::visit_target_symbol to behave differently if this
flag is set.  (Other $var sources like markers might need this sort of
treatment too.)

Another possibility is to let individual variables/expressions be marked with
?, as in $?var, but that might require more guesswork from the user than
should be expected of her.

-- 
           Summary: optional $context variables
           Product: systemtap
           Version: unspecified
            Status: NEW
          Severity: normal
          Priority: P2
         Component: translator
        AssignedTo: systemtap at sources dot redhat dot com
        ReportedBy: fche at redhat dot com


http://sourceware.org/bugzilla/show_bug.cgi?id=7071

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