[libc] add an defense for reentrant exit

Author: SchrodingerZhu

libc/src/__support/threads/thread.cpp

@@ -154,6 +154,9 @@ ThreadAtExitCallbackMgr *get_thread_atexit_callback_mgr() {
 }
 
 void call_atexit_callbacks(ThreadAttributes *attrib) {
+  if (attrib->dtors_called)
+    return;
+  attrib->dtors_called = true;
   attrib->atexit_callback_mgr->call();
   for (size_t i = 0; i < TSS_KEY_COUNT; ++i) {
     TSSValueUnit &unit = tss_values[i];

libc/src/__support/threads/thread.h

@@ -109,12 +109,14 @@ struct alignas(STACK_ALIGNMENT) ThreadAttributes {
   ThreadReturnValue retval;
   ThreadAtExitCallbackMgr *atexit_callback_mgr;
   void *platform_data;
+  bool dtors_called;
 
-  constexpr ThreadAttributes()
+  LIBC_INLINE constexpr ThreadAttributes()
       : detach_state(uint32_t(DetachState::DETACHED)), stack(nullptr),
         stacksize(0), guardsize(0), tls(0), tls_size(0), owned_stack(false),
         tid(-1), style(ThreadStyle::POSIX), retval(),
-        atexit_callback_mgr(nullptr), platform_data(nullptr) {}
+        atexit_callback_mgr(nullptr), platform_data(nullptr),
+        dtors_called(false) {}
 };
 
 using TSSDtor = void(void *);

libc/test/integration/src/__support/threads/CMakeLists.txt

@@ -35,3 +35,14 @@ add_integration_test(
   DEPENDS
     libc.src.__support.threads.thread
 )
+
+add_integration_test(
+  double_exit_test
+  SUITE
+    libc-support-threads-integration-tests
+  SRCS
+    double_exit_test.cpp
+  DEPENDS
+    libc.src.__support.threads.thread
+    libc.src.stdlib.exit
+)

libc/test/integration/src/__support/threads/double_exit_test.cpp

@@ -0,0 +1,23 @@
+//===-- Test handling of thread local data --------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/__support/threads/thread.h"
+#include "src/stdlib/exit.h"
+#include "test/IntegrationTest/test.h"
+
+extern "C" {
+[[gnu::weak]]
+void *__dso_handle = nullptr;
+int __cxa_thread_atexit_impl(void (*func)(void *), void *arg, void *dso);
+}
+
+TEST_MAIN() {
+  __cxa_thread_atexit_impl([](void *) { LIBC_NAMESPACE::exit(0); }, nullptr,
+                           __dso_handle);
+  return 0;
+}

libc/test/integration/src/__support/threads/main_exit_test.cpp

@@ -14,7 +14,6 @@ bool called = false;
 extern "C" {
 [[gnu::weak]]
 void *__dso_handle = nullptr;
-
 int __cxa_thread_atexit_impl(void (*func)(void *), void *arg, void *dso);
 }