[gcc r11-6086] libstdc++: Fix the test for rvalue stream extraction

[Ville Voutilainen]

https://gcc.gnu.org/g:4e096e0ff8c428572353a519cdf8726ef3f70f73

commit r11-6086-g4e096e0ff8c428572353a519cdf8726ef3f70f73
Author: Ville Voutilainen <ville.voutilainen@gmail.com>
Date:   Tue Dec 15 12:05:51 2020 +0200

    libstdc++: Fix the test for rvalue stream extraction
    
    libstdc++-v3/ChangeLog:
    
            * testsuite/27_io/rvalue_streams.cc: Run the extraction to a char*
            for C++17 and lower only.

Diff:
---
 libstdc++-v3/testsuite/27_io/rvalue_streams.cc | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libstdc++-v3/testsuite/27_io/rvalue_streams.cc b/libstdc++-v3/testsuite/27_io/rvalue_streams.cc
index ad4d11c7cf3..487aa4deedd 100644
--- a/libstdc++-v3/testsuite/27_io/rvalue_streams.cc
+++ b/libstdc++-v3/testsuite/27_io/rvalue_streams.cc
@@ -53,7 +53,9 @@ test02()
   VERIFY( x.as_rvalue == true );
 
   char arr[2];
+#if __cplusplus <= 201703L
   std::istringstream("x") >> &arr[0];
+#endif
   std::istringstream("x") >> arr;
 }