support for a brief backtrace format

This only prints symbol+offset, or an address if the symbol isn't
known.

* runtime/runtime.h (SYM_VERBOSE_NO, SYM_VERBOSE_FULL,
  SYM_VERBOSE_BRIEF): new constants
* runtime/stack.c (_stp_stack_print): support brief format
* runtime/sym.c (_stp_func_print): ditto
* tapset/ucontext-unwind.stp (print_ubacktrace_brief): new function
* testsuite/systemtap.context/fib.c: new test program
* testsuite/systemtap.context/fib.stp: new test
* testsuite/systemtap.context/fib.exp: new test

1 files changed, 17 insertions, 0 deletions

diff --git a/testsuite/systemtap.context/fib.stp b/testsuite/systemtap.context/fib.stp
new file mode 100644
index 00000000..85c2fc1d
--- /dev/null
+++ b/testsuite/systemtap.context/fib.stp
@@ -0,0 +1,17 @@
+global depth = 0
+global max_depth = 0
+
+probe process("fib").function("fib").call {
+    depth++
+    if (depth > max_depth) {
+            max_depth = depth
+    }
+}
+
+probe process("fib").function("fib").return {
+    if (depth == max_depth) {
+            print_ubacktrace_brief()
+            printf("\n")
+    }
+    depth--
+}