PR11346: Move the skip-badvars logic into const-folding

The const_folder is where we prune constant expressions, like
conditionals based on a @defined($foo), so we want to give this a chance
to work before skip-badvars comes in and throws a warning.

As an added bonus, this makes skip-badvars more generic, so it will work
even for non-dwarf $target variables.

* elaborate.cxx (const_folder::visit_target_symbol): Enact skip-badvars.
* tapsets.cxx (dwarf_var_expanding_visitor::visit_target_symbol): Don't
  worry about badvars here anymore.  Save the error now, clean up later.
* testsuite/semok/badvar_undefined.stp: Test that @defined with
  skip-badvars doesn't throw any warnings.

1 files changed, 7 insertions, 0 deletions

diff --git a/testsuite/semok/badvar_undefined.stp b/testsuite/semok/badvar_undefined.stp
new file mode 100755
index 00000000..05023ef0
--- /dev/null
+++ b/testsuite/semok/badvar_undefined.stp
@@ -0,0 +1,7 @@
+#!/bin/sh
+
+# PR11346: We shouldn't even see a warning when a would-be skip-badvars
+# replacement is masked by a @defined condition.
+
+stap -W -p2 --skip-badvars -e 'probe kernel.function("sys_getxattr")
+{ printf("%s\n", user_string(@defined($pathname) ? $pathname : $path)) }'