From 6e9ab669b584496dd628700d0d69bd20c5c12ca7 Mon Sep 17 00:00:00 2001
From: Mike Crowe <mac@mcrowe.com>
Date: Sun, 21 Sep 2025 17:15:52 +0100
Subject: [PATCH] libstdc++: Add negative this_thread::sleep tests [PR116586]

Add tests to ensure that std::this_thread::sleep_for() and
std::this_thread::sleep_until() cope with being passed negative times
correctly. These tests prove that the functions don't suffer from
libstdc++/PR116586, and will stay that way.

libstdc++-v3/ChangeLog:

	PR libstdc++/116586
	* testsuite/30_threads/this_thread/sleep_for.cc: Add
	test_negative() test.
	* testsuite/30_threads/this_thread/sleep_until.cc: Make existing
	test use both system_clock and steady_clock. Add test_negative()
	test.

Signed-off-by: Mike Crowe <mac@mcrowe.com>
---
 .../30_threads/this_thread/sleep_for.cc       | 13 ++++++++++
 .../30_threads/this_thread/sleep_until.cc     | 26 ++++++++++++++++---
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/testsuite/30_threads/this_thread/sleep_for.cc b/libstdc++-v3/testsuite/30_threads/this_thread/sleep_for.cc
index 3f55ccc12aa5..5b0518d6bb9f 100644
--- a/libstdc++-v3/testsuite/30_threads/this_thread/sleep_for.cc
+++ b/libstdc++-v3/testsuite/30_threads/this_thread/sleep_for.cc
@@ -37,7 +37,20 @@ test01()
   VERIFY( (chr::system_clock::now() - begin) >= ms );
 }
 
+void
+test_negative()
+{
+  chr::system_clock::time_point begin = chr::system_clock::now();
+
+  std::this_thread::sleep_for(-chr::hours(8));
+
+  // That should have completed immediately, but be generous because we don't
+  // want spurious failures on busy machines.
+  VERIFY( (chr::system_clock::now() - begin) < chr::seconds(10) );
+}
+
 int main()
 {
   test01();
+  test_negative();
 }
diff --git a/libstdc++-v3/testsuite/30_threads/this_thread/sleep_until.cc b/libstdc++-v3/testsuite/30_threads/this_thread/sleep_until.cc
index 1fb82b671772..8c70c2ee78fd 100644
--- a/libstdc++-v3/testsuite/30_threads/this_thread/sleep_until.cc
+++ b/libstdc++-v3/testsuite/30_threads/this_thread/sleep_until.cc
@@ -26,18 +26,36 @@
 
 namespace chr = std::chrono;
 
+template <typename Clock>
 void
 test01()
 {
-  chr::system_clock::time_point begin = chr::system_clock::now();
+  typename Clock::time_point begin = Clock::now();
   chr::microseconds ms(500);
 
-  std::this_thread::sleep_until(chr::system_clock::now() + ms);
+  std::this_thread::sleep_until(Clock::now() + ms);
 
-  VERIFY( (chr::system_clock::now() - begin) >= ms );
+  VERIFY( (Clock::now() - begin) >= ms );
+}
+
+template <typename Clock>
+void
+test_negative()
+{
+  typename Clock::time_point begin = Clock::now();
+
+  typename Clock::time_point tp(-chr::hours(8));
+  std::this_thread::sleep_until(tp);
+
+  // That should have completed immediately, but be generous because we don't
+  // want spurious failures on busy machines.
+  VERIFY( (Clock::now() - begin) < chr::seconds(10) );
 }
 
 int main()
 {
-  test01();
+  test01<chr::steady_clock>();
+  test01<chr::system_clock>();
+  test_negative<chr::steady_clock>();
+  test_negative<chr::system_clock>();
 }
-- 
2.47.3