Initial implementation of __cxa_thread_atexit_impl

  This is initial implementations; does not yet handle
  dlclose - undefined behavior, needs linker support to
  handle it right.

Bug: 19800080
Bug: 16696563
Change-Id: I7a3e21ed7f7ec01e62ea1b7cb2ab253590ea0686
diff --git a/libc/bionic/__cxa_thread_atexit_impl.cpp b/libc/bionic/__cxa_thread_atexit_impl.cpp
new file mode 100644
index 0000000..9ae6dfd
--- /dev/null
+++ b/libc/bionic/__cxa_thread_atexit_impl.cpp
@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2015 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 <sys/cdefs.h>
+
+struct thread_local_dtor {
+  void (*func) (void *);
+  void *arg;
+  void *dso_handle; // unused...
+  thread_local_dtor* next;
+};
+
+__thread thread_local_dtor* thread_local_dtors = nullptr;
+
+extern "C" int __cxa_thread_atexit_impl(void (*func) (void *), void *arg, void *dso_handle) {
+  thread_local_dtor* dtor = new thread_local_dtor();
+
+  dtor->func = func;
+  dtor->arg = arg;
+  dtor->dso_handle = dso_handle;
+  dtor->next = thread_local_dtors;
+
+  thread_local_dtors = dtor;
+
+  return 0;
+}
+
+extern "C" __LIBC_HIDDEN__ void __cxa_thread_finalize() {
+  while (thread_local_dtors != nullptr) {
+    thread_local_dtor* current = thread_local_dtors;
+    thread_local_dtors = current->next;
+
+    current->func(current->arg);
+    delete current;
+  }
+}