PR5930: Address-op for $target and @cast members

This allows the '&' operator to get the address of @cast and $target
variable expressions.

* staptree.h (target_symbol): add addressof field
* staptree.cxx (target_symbol::print): print '&' for addressof
  (cast_op::print): ditto
* parse.cxx (parser::parse_value): allow '&' prefix on $target/@cast
* dwflpp.cxx (dwflpp::translate_final_fetch_or_store): allow taking the
  computed address without actually doing a final fetch.
* tapset* (*::visit_target_symbol): throw errors for $vars w/o addresses
* testsuite/systemtap.base/cast.stp: add &@cast test
* testsuite/semok/target_addr.stp: test '&' on different member types
* testsuite/semko/target_addr?.stp: test failure on bitfields/registers

1 files changed, 6 insertions, 0 deletions

diff --git a/testsuite/semko/target_addr1.stp b/testsuite/semko/target_addr1.stp
new file mode 100755
index 00000000..cac3aab2
--- /dev/null
+++ b/testsuite/semko/target_addr1.stp
@@ -0,0 +1,6 @@
+#! stap -p2
+
+// can't take the address of bitfields
+probe kernel.function("release_task") {
+    println(& $p->did_exec)  // unsigned:1
+}