[gcc r12-3637] libstdc++: Fix last std::tuple constructor missing 'constexpr' [PR102270]

[gcc r12-3637] libstdc++: Fix last std::tuple constructor missing 'constexpr' [PR102270]

[Jonathan Wakely]

https://gcc.gnu.org/g:1fa2c5a695bb962ffcf8abed49f69cdcc59d0e61

commit r12-3637-g1fa2c5a695bb962ffcf8abed49f69cdcc59d0e61
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Sep 17 12:27:02 2021 +0100

    libstdc++: Fix last std::tuple constructor missing 'constexpr' [PR102270]
    
    Also rename the test so it actually runs.
    
    Signed-off-by: Jonathan Wakely <jwakely@redhat.com>
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/102270
            * include/std/tuple (_Tuple_impl): Add constexpr to constructor
            missed in previous patch.
            * testsuite/20_util/tuple/cons/102270.C: Moved to...
            * testsuite/20_util/tuple/cons/102270.cc: ...here.
            * testsuite/util/testsuite_allocator.h (SimpleAllocator): Add
            constexpr to constructor so it can be used for C++20 tests.

Diff:
---
 libstdc++-v3/include/std/tuple                                    | 1 +
 libstdc++-v3/testsuite/20_util/tuple/cons/{102270.C => 102270.cc} | 3 +++
 libstdc++-v3/testsuite/util/testsuite_allocator.h                 | 2 +-
 3 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/libstdc++-v3/include/std/tuple b/libstdc++-v3/include/std/tuple
index 6f0dc6346e1..120c80a2b78 100644
--- a/libstdc++-v3/include/std/tuple
+++ b/libstdc++-v3/include/std/tuple
@@ -330,6 +330,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	{ }
 
       template<typename _Alloc>
+	_GLIBCXX20_CONSTEXPR
 	_Tuple_impl(allocator_arg_t __tag, const _Alloc& __a,
 		    const _Head& __head, const _Tail&... __tail)
 	: _Inherited(__tag, __a, __tail...),
diff --git a/libstdc++-v3/testsuite/20_util/tuple/cons/102270.C b/libstdc++-v3/testsuite/20_util/tuple/cons/102270.cc
similarity index 95%
rename from libstdc++-v3/testsuite/20_util/tuple/cons/102270.C
rename to libstdc++-v3/testsuite/20_util/tuple/cons/102270.cc
index 998329817c7..5500cacab6d 100644
--- a/libstdc++-v3/testsuite/20_util/tuple/cons/102270.C
+++ b/libstdc++-v3/testsuite/20_util/tuple/cons/102270.cc
@@ -56,6 +56,9 @@ constexpr bool construct_using_allocator()
 
   std::tuple<X1a, X1a, X1b, X1b> t1a1b(std::allocator_arg, a, 1, i, 1, i);
 
+  const int c = 0;
+  std::tuple<int, int> tii(std::allocator_arg, a, c, c);
+
   return true;
 }
 static_assert( construct_using_allocator() );
diff --git a/libstdc++-v3/testsuite/util/testsuite_allocator.h b/libstdc++-v3/testsuite/util/testsuite_allocator.h
index 1f7912ea6eb..b5b402858a6 100644
--- a/libstdc++-v3/testsuite/util/testsuite_allocator.h
+++ b/libstdc++-v3/testsuite/util/testsuite_allocator.h
@@ -514,7 +514,7 @@ namespace __gnu_test
     {
       typedef Tp value_type;
 
-      SimpleAllocator() noexcept { }
+      constexpr SimpleAllocator() noexcept { }
 
       template <class T>
         SimpleAllocator(const SimpleAllocator<T>&) { }