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, 7 insertions, 0 deletions

diff --git a/main.cxx b/main.cxx
index b494ba2b..890f65bc 100644
--- a/main.cxx
+++ b/main.cxx
@@ -134,6 +134,8 @@ usage (systemtap_session& s, int exitcode)
 #endif
   // Formerly present --ignore-{vmlinux,dwarf} options are for testsuite use
   // only, and don't belong in the eyesight of a plain user.
+    << "   --skip-badvars" << endl
+    << "              overlook context of bad $ variables" << endl
     << endl
     ;
 
@@ -431,12 +433,14 @@ main (int argc, char * const argv [])
 #define LONG_OPT_IGNORE_VMLINUX 3
 #define LONG_OPT_IGNORE_DWARF 4
 #define LONG_OPT_VERBOSE_PASS 5
+#define LONG_OPT_SKIP_BADVARS 6
       // NB: also see find_hash(), usage(), switch stmt below, stap.1 man page
       static struct option long_options[] = {
         { "kelf", 0, &long_opt, LONG_OPT_KELF },
         { "kmap", 2, &long_opt, LONG_OPT_KMAP },
         { "ignore-vmlinux", 0, &long_opt, LONG_OPT_IGNORE_VMLINUX },
         { "ignore-dwarf", 0, &long_opt, LONG_OPT_IGNORE_DWARF },
+	{ "skip-badvars", 0, &long_opt, LONG_OPT_SKIP_BADVARS },
         { "vp", 1, &long_opt, LONG_OPT_VERBOSE_PASS },
         { NULL, 0, NULL, 0 }
       };
@@ -698,6 +702,9 @@ main (int argc, char * const argv [])
                 // NB: we don't do this: s.last_pass = strlen(optarg);
                 break;
               }
+	    case LONG_OPT_SKIP_BADVARS:
+	      s.skip_badvars = true;
+	      break;
             default:
               cerr << "Internal error parsing command arguments." << endl;
               usage(s, 1);