Test unwinding through a signal handler.

Also make backtrace_testlib.c C++.

Bug: 34468756
Test: Ran new unit test on host x86, host x86_64, angler (32 bit, 64 bit),
Test: fugu.
Change-Id: Ia810f596c2df56cd56e8ab17e6c19be0c48d737f
diff --git a/libbacktrace/backtrace_testlib.cpp b/libbacktrace/backtrace_testlib.cpp
new file mode 100644
index 0000000..3081d64
--- /dev/null
+++ b/libbacktrace/backtrace_testlib.cpp
@@ -0,0 +1,86 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <libunwind.h>
+#include <signal.h>
+#include <stdio.h>
+
+#include "backtrace_testlib.h"
+
+void test_loop_forever() {
+  while (1)
+    ;
+}
+
+void test_signal_handler(int) { test_loop_forever(); }
+
+void test_signal_action(int, siginfo_t*, void*) { test_loop_forever(); }
+
+int test_level_four(int one, int two, int three, int four, void (*callback_func)(void*),
+                    void* data) {
+  if (callback_func != NULL) {
+    callback_func(data);
+  } else {
+    while (1)
+      ;
+  }
+  return one + two + three + four;
+}
+
+int test_level_three(int one, int two, int three, int four, void (*callback_func)(void*),
+                     void* data) {
+  return test_level_four(one + 3, two + 6, three + 9, four + 12, callback_func, data) + 3;
+}
+
+int test_level_two(int one, int two, int three, int four, void (*callback_func)(void*), void* data) {
+  return test_level_three(one + 2, two + 4, three + 6, four + 8, callback_func, data) + 2;
+}
+
+int test_level_one(int one, int two, int three, int four, void (*callback_func)(void*), void* data) {
+  return test_level_two(one + 1, two + 2, three + 3, four + 4, callback_func, data) + 1;
+}
+
+int test_recursive_call(int level, void (*callback_func)(void*), void* data) {
+  if (level > 0) {
+    return test_recursive_call(level - 1, callback_func, data) + level;
+  } else if (callback_func != NULL) {
+    callback_func(data);
+  } else {
+    while (1) {
+    }
+  }
+  return 0;
+}
+
+typedef struct {
+  unw_context_t* unw_context;
+  volatile int* exit_flag;
+} GetContextArg;
+
+static void GetContextAndExit(void* data) {
+  GetContextArg* arg = (GetContextArg*)data;
+  unw_getcontext(arg->unw_context);
+  // Don't touch the stack anymore.
+  while (*arg->exit_flag == 0) {
+  }
+}
+
+void test_get_context_and_wait(unw_context_t* unw_context, volatile int* exit_flag) {
+  GetContextArg arg;
+  arg.unw_context = unw_context;
+  arg.exit_flag = exit_flag;
+  test_level_one(1, 2, 3, 4, GetContextAndExit, &arg);
+}