[libc-commits] [libc] [libc] ensure tls dtors are called in main thread (PR #133641)

[Schrodinger ZHU Yifan via libc-commits]

https://github.com/SchrodingerZhu updated https://github.com/llvm/llvm-project/pull/133641

>From 175ae9a1e62fd06977a4646d46aaca1b9fa526e3 Mon Sep 17 00:00:00 2001
From: Schrodinger ZHU Yifan <i at zhuyi.fan>
Date: Sun, 30 Mar 2025 12:15:40 -0400
Subject: [PATCH] [libc] ensure tls dtors are called in main thread

---
 libc/src/__support/threads/thread.cpp         |  5 ++++
 libc/src/__support/threads/thread.h           |  6 ++--
 libc/src/stdlib/exit.cpp                      |  4 +++
 .../src/__support/threads/CMakeLists.txt      | 21 +++++++++++++
 .../__support/threads/double_exit_test.cpp    | 23 ++++++++++++++
 .../src/__support/threads/main_exit_test.cpp  | 30 +++++++++++++++++++
 6 files changed, 87 insertions(+), 2 deletions(-)
 create mode 100644 libc/test/integration/src/__support/threads/double_exit_test.cpp
 create mode 100644 libc/test/integration/src/__support/threads/main_exit_test.cpp

diff --git a/libc/src/__support/threads/thread.cpp b/libc/src/__support/threads/thread.cpp
index 6f6b75be5766d..c7135596622c6 100644
--- a/libc/src/__support/threads/thread.cpp
+++ b/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];
@@ -163,6 +166,8 @@ void call_atexit_callbacks(ThreadAttributes *attrib) {
   }
 }
 
+extern "C" void __cxa_thread_finalize() { call_atexit_callbacks(self.attrib); }
+
 } // namespace internal
 
 cpp::optional<unsigned int> new_tss_key(TSSDtor *dtor) {
diff --git a/libc/src/__support/threads/thread.h b/libc/src/__support/threads/thread.h
index f2b1f6bbb253d..f7710fde2c70d 100644
--- a/libc/src/__support/threads/thread.h
+++ b/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 *);
diff --git a/libc/src/stdlib/exit.cpp b/libc/src/stdlib/exit.cpp
index 28a6f8a63c0c6..097a52339e5e8 100644
--- a/libc/src/stdlib/exit.cpp
+++ b/libc/src/stdlib/exit.cpp
@@ -14,8 +14,12 @@
 namespace LIBC_NAMESPACE_DECL {
 
 extern "C" void __cxa_finalize(void *);
+extern "C" [[gnu::weak]] void __cxa_thread_finalize();
 
+// TODO: use recursive mutex to protect this routine.
 [[noreturn]] LLVM_LIBC_FUNCTION(void, exit, (int status)) {
+  if (__cxa_thread_finalize)
+    __cxa_thread_finalize();
   __cxa_finalize(nullptr);
   internal::exit(status);
 }
diff --git a/libc/test/integration/src/__support/threads/CMakeLists.txt b/libc/test/integration/src/__support/threads/CMakeLists.txt
index 5a12d28ada3fd..40e96681b1207 100644
--- a/libc/test/integration/src/__support/threads/CMakeLists.txt
+++ b/libc/test/integration/src/__support/threads/CMakeLists.txt
@@ -25,3 +25,24 @@ add_integration_test(
   DEPENDS
     libc.src.__support.threads.thread
 )
+
+add_integration_test(
+  main_exit_test
+  SUITE
+    libc-support-threads-integration-tests
+  SRCS
+    main_exit_test.cpp
+  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
+)
diff --git a/libc/test/integration/src/__support/threads/double_exit_test.cpp b/libc/test/integration/src/__support/threads/double_exit_test.cpp
new file mode 100644
index 0000000000000..e4a163644a970
--- /dev/null
+++ b/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;
+}
diff --git a/libc/test/integration/src/__support/threads/main_exit_test.cpp b/libc/test/integration/src/__support/threads/main_exit_test.cpp
new file mode 100644
index 0000000000000..c90e4e569cfba
--- /dev/null
+++ b/libc/test/integration/src/__support/threads/main_exit_test.cpp
@@ -0,0 +1,30 @@
+//===-- 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 "test/IntegrationTest/test.h"
+
+bool called = false;
+
+extern "C" {
+[[gnu::weak]]
+void *__dso_handle = nullptr;
+int __cxa_thread_atexit_impl(void (*func)(void *), void *arg, void *dso);
+}
+
+[[gnu::destructor]]
+void destructor() {
+  if (!called)
+    __builtin_trap();
+}
+
+TEST_MAIN() {
+  __cxa_thread_atexit_impl([](void *) { called = true; }, nullptr,
+                           __dso_handle);
+  return 0;
+}