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, 9 insertions, 0 deletions

diff --git a/testsuite/systemtap.base/cast.stp b/testsuite/systemtap.base/cast.stp
index e2505000..bb889bb8 100644
--- a/testsuite/systemtap.base/cast.stp
+++ b/testsuite/systemtap.base/cast.stp
@@ -33,6 +33,15 @@ probe begin
     else
         printf("sa_data %d != %d\n", data, cast_data)
 
+    // Compare usage counter values through a struct address
+    usage = @cast(curr, "task_struct")->usage->counter
+    pusage = & @cast(curr, "task_struct")->usage
+    cast_usage = @cast(pusage, "atomic_t")->counter
+    if (usage == cast_usage)
+        println("usage OK")
+    else
+        printf("usage %d != %d\n", usage, cast_usage)
+
     exit()
 }