libstdc++: Remove redundant overflow check for futex timeout [PR 93456]

The relative_timespec function already checks for the case where the
specified timeout is in the past, so the difference can never be
negative. That means we dn't need to check if it's more negative than
the minimum time_t value.

libstdc++-v3/ChangeLog:

	PR libstdc++/93456
	* src/c++11/futex.cc (relative_timespec): Remove redundant check
	negative values.
	* testsuite/30_threads/future/members/wait_until_overflow.cc: Moved to...
	* testsuite/30_threads/future/members/93456.cc: ...here.

diff --git a/libstdc++-v3/src/c++11/futex.cc b/libstdc++-v3/src/c++11/futex.cc
index 15959cebee57c6c785437ac27525cdf7d84a3a8f..c008798318c93670deaf7acd733312f74b04a5b2 100644 (file)
--- a/libstdc++-v3/src/c++11/futex.cc
+++ b/libstdc++-v3/src/c++11/futex.cc
@@ -73,21 +73,23 @@ namespace
        return rt;
       }
 
-    auto rel_s = abs_s.count() - now_s;
+    const auto rel_s = abs_s.count() - now_s;
 
-    // Avoid overflows
+    // Convert the absolute timeout to a relative timeout, without overflow.
     if (rel_s > __int_traits<time_t>::__max) [[unlikely]]
-      rel_s = __int_traits<time_t>::__max;
-    else if (rel_s < __int_traits<time_t>::__min) [[unlikely]]
-      rel_s = __int_traits<time_t>::__min;
-
-    // Convert the absolute timeout value to a relative timeout
-    rt.tv_sec = rel_s;
-    rt.tv_nsec = abs_ns.count() - now_ns;
-    if (rt.tv_nsec < 0)
       {
-       rt.tv_nsec += 1000000000;
-       --rt.tv_sec;
+       rt.tv_sec = __int_traits<time_t>::__max;
+       rt.tv_nsec = 999999999;
+      }
+    else
+      {
+       rt.tv_sec = rel_s;
+       rt.tv_nsec = abs_ns.count() - now_ns;
+       if (rt.tv_nsec < 0)
+         {
+           rt.tv_nsec += 1000000000;
+           --rt.tv_sec;
+         }
       }
 
     return rt;

diff --git a/libstdc++-v3/testsuite/30_threads/future/members/93456.cc b/libstdc++-v3/testsuite/30_threads/future/members/93456.cc
new file mode 100644 (file)
index 0000000..8d6a514
--- /dev/null
+++ b/libstdc++-v3/testsuite/30_threads/future/members/93456.cc
@@ -0,0 +1,48 @@
+// { dg-do run }
+// { dg-additional-options "-pthread" { target pthread } }
+// { dg-require-effective-target c++11 }
+// { dg-require-gthreads "" }
+
+// Copyright (C) 2020 Free Software Foundation, Inc.
+//
+// This file is part of the GNU ISO C++ Library.  This library is free
+// software; you can redistribute it and/or modify it under the
+// terms of the GNU General Public License as published by the
+// Free Software Foundation; either version 3, or (at your option)
+// any later version.
+
+// This library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License along
+// with this library; see the file COPYING3.  If not see
+// <http://www.gnu.org/licenses/>.
+
+
+#include <future>
+#include <chrono>
+#include <climits>
+#include <testsuite_hooks.h>
+
+namespace chrono = std::chrono;
+
+void test01()
+{
+  std::future<void> fut = std::async(std::launch::async, [] {
+    std::this_thread::sleep_for(chrono::seconds(4));
+  });
+
+  // A time in the distant future, but which overflows 32-bit time_t:
+  auto then = chrono::system_clock::now() + chrono::seconds(UINT_MAX + 2LL);
+  auto status = fut.wait_until(then);
+  // The wait_until call should have waited for the result to be ready.
+  // If converting the time_point to time_t overflows, it will timeout.
+  VERIFY(status == std::future_status::ready);
+}
+
+int main()
+{
+  test01();
+}

diff --git a/libstdc++-v3/testsuite/30_threads/future/members/wait_until_overflow.cc b/libstdc++-v3/testsuite/30_threads/future/members/wait_until_overflow.cc
deleted file mode 100644 (file)
index 8d6a514..0000000
--- a/libstdc++-v3/testsuite/30_threads/future/members/wait_until_overflow.cc
+++ /dev/null
@@ -1,48 +0,0 @@
-// { dg-do run }
-// { dg-additional-options "-pthread" { target pthread } }
-// { dg-require-effective-target c++11 }
-// { dg-require-gthreads "" }
-
-// Copyright (C) 2020 Free Software Foundation, Inc.
-//
-// This file is part of the GNU ISO C++ Library.  This library is free
-// software; you can redistribute it and/or modify it under the
-// terms of the GNU General Public License as published by the
-// Free Software Foundation; either version 3, or (at your option)
-// any later version.
-
-// This library is distributed in the hope that it will be useful,
-// but WITHOUT ANY WARRANTY; without even the implied warranty of
-// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-// GNU General Public License for more details.
-
-// You should have received a copy of the GNU General Public License along
-// with this library; see the file COPYING3.  If not see
-// <http://www.gnu.org/licenses/>.
-
-
-#include <future>
-#include <chrono>
-#include <climits>
-#include <testsuite_hooks.h>
-
-namespace chrono = std::chrono;
-
-void test01()
-{
-  std::future<void> fut = std::async(std::launch::async, [] {
-    std::this_thread::sleep_for(chrono::seconds(4));
-  });
-
-  // A time in the distant future, but which overflows 32-bit time_t:
-  auto then = chrono::system_clock::now() + chrono::seconds(UINT_MAX + 2LL);
-  auto status = fut.wait_until(then);
-  // The wait_until call should have waited for the result to be ready.
-  // If converting the time_point to time_t overflows, it will timeout.
-  VERIFY(status == std::future_status::ready);
-}
-
-int main()
-{
-  test01();
-}