[libcxx-commits] [libcxx] [libc++] Deprecate non-standard std::launch::any extension (PR #173397)

[via libcxx-commits]

https://github.com/sohail103 updated https://github.com/llvm/llvm-project/pull/173397

>From f7f6ed86e88f7cf441d800cb586cca1fbda05069 Mon Sep 17 00:00:00 2001
From: sohail103 <sohailraj.satapathy at gmail.com>
Date: Tue, 23 Dec 2025 17:07:21 +0000
Subject: [PATCH] [libc++] Deprecate non-standard std::launch::any extension

std::launch::any was a draft C++11 feature that was removed before the final standard.
It has remained in libc++ as an extension. This patch marks it as deprecated to warn users
who might be relying on it unintentionally.

- Replaced internal usage of std::launch::any in std::async with standard flags.
- Added a verify test to check for the deprecation warning.
- Updated existing tests to expect the deprecation warning.

Fixes #173219
---
 libcxx/include/future                         |  4 ++--
 .../diagnostics/future.nodiscard.verify.cpp   |  1 +
 .../futures/launch_any_deprecated.verify.cpp  | 21 +++++++++++++++++++
 .../futures/futures.async/async.pass.cpp      |  2 +-
 .../futures/futures.overview/launch.pass.cpp  |  8 +++----
 5 files changed, 29 insertions(+), 7 deletions(-)
 create mode 100644 libcxx/test/libcxx/thread/futures/launch_any_deprecated.verify.cpp

diff --git a/libcxx/include/future b/libcxx/include/future
index c249bc5e7938f..631572c6ebe8d 100644
--- a/libcxx/include/future
+++ b/libcxx/include/future
@@ -434,7 +434,7 @@ struct is_error_code_enum<future_errc::__lx> : public true_type {};
 #    endif
 
 // enum class launch
-_LIBCPP_DECLARE_STRONG_ENUM(launch){async = 1, deferred = 2, any = async | deferred};
+_LIBCPP_DECLARE_STRONG_ENUM(launch){async = 1, deferred = 2, any _LIBCPP_DEPRECATED = async | deferred};
 _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(launch)
 
 #    ifndef _LIBCPP_CXX03_LANG
@@ -1872,7 +1872,7 @@ async(launch __policy, _Fp&& __f, _Args&&... __args) {
 template <class _Fp, class... _Args>
 [[__nodiscard__]] inline _LIBCPP_HIDE_FROM_ABI future<__invoke_result_t<__decay_t<_Fp>, __decay_t<_Args>...> >
 async(_Fp&& __f, _Args&&... __args) {
-  return std::async(launch::any, std::forward<_Fp>(__f), std::forward<_Args>(__args)...);
+  return std::async(launch::async | launch::deferred, std::forward<_Fp>(__f), std::forward<_Args>(__args)...);
 }
 
 #    endif // C++03
diff --git a/libcxx/test/libcxx/diagnostics/future.nodiscard.verify.cpp b/libcxx/test/libcxx/diagnostics/future.nodiscard.verify.cpp
index cc5c6135d109b..2eadd429b1629 100644
--- a/libcxx/test/libcxx/diagnostics/future.nodiscard.verify.cpp
+++ b/libcxx/test/libcxx/diagnostics/future.nodiscard.verify.cpp
@@ -19,4 +19,5 @@
 void test() {
   std::async([]() {});                   // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
   std::async(std::launch::any, []() {}); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+                                         // expected-warning at -1 {{'any' is deprecated}}
 }
diff --git a/libcxx/test/libcxx/thread/futures/launch_any_deprecated.verify.cpp b/libcxx/test/libcxx/thread/futures/launch_any_deprecated.verify.cpp
new file mode 100644
index 0000000000000..aa6ed5cccecb6
--- /dev/null
+++ b/libcxx/test/libcxx/thread/futures/launch_any_deprecated.verify.cpp
@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// <future>
+
+// enum class launch;
+
+// Verify that std::launch::any is deprecated.
+// It was a draft C++11 feature that was removed, but libc++ kept it as an extension.
+
+#include <future>
+
+void test() {
+  auto l = std::launch::any; // expected-warning {{'any' is deprecated}}
+  (void)l;
+}
diff --git a/libcxx/test/std/thread/futures/futures.async/async.pass.cpp b/libcxx/test/std/thread/futures/futures.async/async.pass.cpp
index 109372b50a311..4327356ca87fa 100644
--- a/libcxx/test/std/thread/futures/futures.async/async.pass.cpp
+++ b/libcxx/test/std/thread/futures/futures.async/async.pass.cpp
@@ -114,7 +114,7 @@ int main(int, char**)
     bool DPID = DefaultPolicyIsDeferred;
 
     std::launch AnyPolicy = std::launch::async | std::launch::deferred;
-    LIBCPP_ASSERT(AnyPolicy == std::launch::any);
+    LIBCPP_ASSERT(AnyPolicy == std::launch::any); // expected-warning {{'any' is deprecated}}
 
     {
         auto checkInt = [](std::future<int>& f) { return f.get() == 3; };
diff --git a/libcxx/test/std/thread/futures/futures.overview/launch.pass.cpp b/libcxx/test/std/thread/futures/futures.overview/launch.pass.cpp
index 37ad2ff4a8645..819765f42c56b 100644
--- a/libcxx/test/std/thread/futures/futures.overview/launch.pass.cpp
+++ b/libcxx/test/std/thread/futures/futures.overview/launch.pass.cpp
@@ -25,19 +25,19 @@
 int main(int, char**)
 {
 #if TEST_STD_VER < 11
-   LIBCPP_STATIC_ASSERT(static_cast<int>(std::launch::any) ==
+   LIBCPP_STATIC_ASSERT(static_cast<int>(std::launch::any) == // expected-warning {{'any' is deprecated}}
                  (static_cast<int>(std::launch::async) | static_cast<int>(std::launch::deferred)), "");
 #else
-    LIBCPP_STATIC_ASSERT(std::launch::any == (std::launch::async | std::launch::deferred), "");
+    LIBCPP_STATIC_ASSERT(std::launch::any == (std::launch::async | std::launch::deferred), ""); // expected-warning {{'any' is deprecated}}
     static_assert(std::launch(0) == (std::launch::async & std::launch::deferred), "");
-    LIBCPP_STATIC_ASSERT(std::launch::any == (std::launch::async ^ std::launch::deferred), "");
+    LIBCPP_STATIC_ASSERT(std::launch::any == (std::launch::async ^ std::launch::deferred), ""); // expected-warning {{'any' is deprecated}}
     LIBCPP_STATIC_ASSERT(std::launch::deferred == ~std::launch::async, "");
     std::launch x = std::launch::async;
     x &= std::launch::deferred;
     assert(x == std::launch(0));
     x = std::launch::async;
     x |= std::launch::deferred;
-    LIBCPP_ASSERT(x == std::launch::any);
+    LIBCPP_ASSERT(x == std::launch::any); // expected-warning {{'any' is deprecated}}
     x ^= std::launch::deferred;
     assert(x == std::launch::async);
 #endif