[committed] libstdc++: Fix move construction of std::tuple with array elements [PR101960]

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  • [committed] libstdc++: Fix move construction of std::tuple with array elements [PR101960]
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Commit Message

Jason Merrill via Gcc-patches Oct. 12, 2021, 3:50 p.m.
The r12-3022 commit only fixed the case where an array is the last
element of the tuple. This fixes the other cases too. We can just define
the move constructor as defaulted, which does the right thing. Changing
the move constructor to be trivial would be an ABI break, but since the
last base class still has a non-trivial move constructor, defining the
derived ones as defaulted doesn't change anything.

libstdc++-v3/ChangeLog:

	PR libstdc++/101960
	* include/std/tuple (_Tuple_impl(_Tuple_impl&&)): Define as
	defauled.
	* testsuite/20_util/tuple/cons/101960.cc: Check tuples with
	array elements before the last element.

Tested powerpc64le-linux. Committed to trunk.
commit 7481021364e75ba583972e15ed421a53988368ea
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Tue Oct 12 15:09:50 2021

    libstdc++: Fix move construction of std::tuple with array elements [PR101960]
    
    The r12-3022 commit only fixed the case where an array is the last
    element of the tuple. This fixes the other cases too. We can just define
    the move constructor as defaulted, which does the right thing. Changing
    the move constructor to be trivial would be an ABI break, but since the
    last base class still has a non-trivial move constructor, defining the
    derived ones as defaulted doesn't change anything.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/101960
            * include/std/tuple (_Tuple_impl(_Tuple_impl&&)): Define as
            defauled.
            * testsuite/20_util/tuple/cons/101960.cc: Check tuples with
            array elements before the last element.

Patch

diff --git a/libstdc++-v3/include/std/tuple b/libstdc++-v3/include/std/tuple
index 94a4f0afd31..aaee0b8826a 100644
--- a/libstdc++-v3/include/std/tuple
+++ b/libstdc++-v3/include/std/tuple
@@ -298,13 +298,7 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
       // 2729. Missing SFINAE on std::pair::operator=
       _Tuple_impl& operator=(const _Tuple_impl&) = delete;
 
-      constexpr
-      _Tuple_impl(_Tuple_impl&& __in)
-      noexcept(__and_<is_nothrow_move_constructible<_Head>,
-		      is_nothrow_move_constructible<_Inherited>>::value)
-      : _Inherited(std::move(_M_tail(__in))),
-	_Base(std::forward<_Head>(_M_head(__in)))
-      { }
+      _Tuple_impl(_Tuple_impl&&) = default;
 
       template<typename... _UElements>
 	constexpr
diff --git a/libstdc++-v3/testsuite/20_util/tuple/cons/101960.cc b/libstdc++-v3/testsuite/20_util/tuple/cons/101960.cc
index f14604cdc69..42d17b182ed 100644
--- a/libstdc++-v3/testsuite/20_util/tuple/cons/101960.cc
+++ b/libstdc++-v3/testsuite/20_util/tuple/cons/101960.cc
@@ -1,4 +1,13 @@ 
 // { dg-do compile { target c++11 } }
 #include <tuple>
+
+// PR libstdc++/101960
+
 std::tuple<int[1]> t;
-auto tt = std::move(t); // PR libstdc++/101960
+auto tt = std::move(t);
+
+std::tuple<int[1], int> t2;
+auto tt2 = std::move(t2);
+
+std::tuple<int[1], int[2], int[3]> t3;
+auto tt3 = std::move(t3);