PR 7071: Optional $context variables fix

* tapsets.cxx (dwarf_var_expanding_visitor::visit_target_symbol):
  Substitute erroneous target symbol with literal 0 if session level
  flag, skip_badvars is set.
* session.h (struct systemtap_session):
  New flag: skip_badvars.
* main.cxx:
  Command line argument --skip-badvars added.
* stap.1.in:
  Entry for new option --skip-badvars.
* NEWS:
  Added blurb for new option now available.
* testsuite/semok/badvar.stp:
  Test case to check added functionality.

1 files changed, 3 insertions, 0 deletions

diff --git a/session.h b/session.h
index bc99385b..ec6c2e3e 100644
--- a/session.h
+++ b/session.h
@@ -123,6 +123,9 @@ struct systemtap_session
   bool ignore_vmlinux;
   bool ignore_dwarf;
 
+  // Skip bad $ vars
+  bool skip_badvars;
+
   // temporary directory for module builds etc.
   // hazardous - it is "rm -rf"'d at exit
   std::string tmpdir;