Make _Unwind_Backtrace() work on ARM.

Summary: Since the personality functions do the actual unwinding on ARM,
and will also stop unwinding when they encounter a handler, we invoke
_Unwind_VRS_Interpret() directly form _Unwind_Backtrace().

To simplify, the logic for decoding an EHT is moved out of
unwindOneFrame() and into its own function, decode_eht_entry(). Unlike
unwindOneFrame(), which could only handle ARM's compact personality
function entries (section 6.3) decode_eht_entry() can handle the generic
entries (section 6.2).

Reviewers: jroelofs

Reviewed By: jroelofs

Subscribers: piman, aemerson, cfe-commits

Differential Revision: http://reviews.llvm.org/D5112

llvm-svn: 216730

1 files changed, 61 insertions, 0 deletions

diff --git a/libcxxabi/test/backtrace_test.cpp b/libcxxabi/test/backtrace_test.cpp
new file mode 100644
index 00000000000..25dccb3229e
--- /dev/null
+++ b/libcxxabi/test/backtrace_test.cpp
@@ -0,0 +1,61 @@
+//===---------------------- backtrace_test.cpp ----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+#include <assert.h>
+#include <unwind.h>
+
+extern "C" _Unwind_Reason_Code
+trace_function(struct _Unwind_Context* context, void* ntraced) {
+  (*reinterpret_cast<size_t*>(ntraced))++;
+  // We should never have a call stack this deep...
+  assert(*reinterpret_cast<size_t*>(ntraced) < 20);
+  return _URC_NO_REASON;
+}
+
+void call3_throw(size_t* ntraced) {
+  try {
+    _Unwind_Backtrace(trace_function, ntraced);
+  } catch (...) {
+    assert(false);
+  }
+}
+
+void call3_nothrow(size_t* ntraced) {
+  _Unwind_Backtrace(trace_function, ntraced);
+}
+
+void call2(size_t* ntraced, bool do_throw) {
+  if (do_throw) {
+    call3_throw(ntraced);
+  } else {
+    call3_nothrow(ntraced);
+  }
+}
+
+void call1(size_t* ntraced, bool do_throw) {
+  call2(ntraced, do_throw);
+}
+
+int main() {
+  size_t throw_ntraced = 0;
+  size_t nothrow_ntraced = 0;
+
+  call1(&nothrow_ntraced, false);
+
+  try {
+    call1(&throw_ntraced, true);
+  } catch (...) {
+    assert(false);
+  }
+
+  // Different platforms (and different runtimes) will unwind a different number
+  // of times, so we can't make any better assumptions than this.
+  assert(nothrow_ntraced > 1);
+  assert(throw_ntraced == nothrow_ntraced); // Make sure we unwind through catch
+  return 0;
+}