libstdc++: Fix for explicit copy ctors in <thread> and <future> [PR106695]

When I changed std::thread and std::async to avoid unnecessary move
construction of temporaries, I introduced a regression where types with
an explicit copy constructor could not be passed to std::thread or
std::async. The fix is to add a constructor instead of using aggregate
initialization of an unnamed temporary.

libstdc++-v3/ChangeLog:

	PR libstdc++/106695
	* include/bits/std_thread.h (thread::_State_impl): Forward
	individual arguments to _Invoker constructor.
	(thread::_Invoker): Add constructor. Delete copies.
	* include/std/future (__future_base::_Deferred_state): Forward
	individual arguments to _Invoker constructor.
	(__future_base::_Async_state_impl): Likewise.
	* testsuite/30_threads/async/106695.cc: New test.
	* testsuite/30_threads/thread/106695.cc: New test.

2 files changed, 50 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/30_threads/async/106695.cc b/libstdc++-v3/testsuite/30_threads/async/106695.cc
new file mode 100644
index 0000000..7499634
--- /dev/null
+++ b/libstdc++-v3/testsuite/30_threads/async/106695.cc
@@ -0,0 +1,29 @@
+// { dg-do compile { target c++11 } }
+// { dg-require-gthreads "" }
+
+// PR libstdc++/106695
+// Explicit copy constructor does not work for a parameter passed via std::async
+
+#include <future>
+
+struct A {
+  A() = default;
+  explicit A(const A&) = default;
+};
+
+void func(const A&) { }
+
+void
+test_async()
+{
+  (void) std::async(std::launch::async, func, A{});
+  (void) std::async(std::launch::deferred, func, A{});
+  (void) std::async(func, A{});
+}
+
+void
+test_task()
+{
+  std::packaged_task<void(const A&)> task(func);
+  task(A{});
+}
diff --git a/libstdc++-v3/testsuite/30_threads/thread/106695.cc b/libstdc++-v3/testsuite/30_threads/thread/106695.cc
new file mode 100644
index 0000000..97e9e92
--- /dev/null
+++ b/libstdc++-v3/testsuite/30_threads/thread/106695.cc
@@ -0,0 +1,21 @@
+// { dg-do compile { target c++11 } }
+// { dg-require-gthreads "" }
+
+// PR libstdc++/106695
+// Explicit copy constructor does not work for a parameter passed via std::async
+
+#include <thread>
+
+struct A {
+  A() = default;
+  explicit A(const A&) = default;
+};
+
+void func(const A&) { }
+
+void
+test_thread()
+{
+  std::thread t(func, A{});
+  t.join();
+}