Avoid creating dangling references in case of nested tuples

for tuple constructors that construct from other tuples.

2015-09-25  Ville Voutilainen  <ville.voutilainen@gmail.com>

	Avoid creating dangling references in case of nested tuples
	for tuple constructors that construct from other tuples.
	* include/std/tuple (_TC::_NonNestedTuple): New.
	* include/std/tuple (tuple::_TNTC): New.
	* include/std/tuple (tuple(const tuple<_UElements...>&),
	tuple(tuple<_UElements...>&&): Use _TNTC.
	* testsuite/20_util/tuple/cons/nested_tuple_construct.cc: New.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@228134 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 60 insertions, 0 deletions

diff --git a/libstdc++-v3/testsuite/20_util/tuple/cons/nested_tuple_construct.cc b/libstdc++-v3/testsuite/20_util/tuple/cons/nested_tuple_construct.cc
new file mode 100644
index 00000000000..32ef3cc0259
--- /dev/null
+++ b/libstdc++-v3/testsuite/20_util/tuple/cons/nested_tuple_construct.cc
@@ -0,0 +1,60 @@
+#include <string>
+#include <tuple>
+#include <testsuite_hooks.h>
+
+static std::string result;
+
+struct X {
+  int state; // this has to be here
+  X() {
+    result += "Def";
+  }
+
+  X(X const&) {
+    result += "Copy";
+  }
+
+  X(X&&) {
+    result += "Move";
+  }
+
+  ~X() {
+    result += "Dtor";
+  }
+};
+
+void f()
+{
+  X v;
+  std::tuple<X> t1{v};
+  std::tuple<std::tuple<X>&&> t2{std::move(t1)};
+  std::tuple<std::tuple<X>> t3{std::move(t2)};
+}
+
+void f2()
+{
+  X v;
+  std::tuple<X> t1{std::move(v)};
+  std::tuple<std::tuple<X>&&> t2{std::move(t1)};
+  std::tuple<std::tuple<X>> t3{std::move(t2)};
+}
+
+void f3()
+{
+  std::tuple<X> t1{X{}};
+  std::tuple<std::tuple<X>&&> t2{std::move(t1)};
+  std::tuple<std::tuple<X>> t3{std::move(t2)};
+}
+
+int main()
+{
+  f();
+  VERIFY(result == "DefCopyMoveDtorDtorDtor");
+  result = "";
+  f2();
+  VERIFY(result == "DefMoveMoveDtorDtorDtor");
+  result = "";
+  f3();
+  VERIFY(result == "DefMoveDtorMoveDtorDtor");
+  result = "";
+}