commit 917efba2dd4ff34336d0d3aa55285ae22503e4aa
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Jun 14 10:58:15 2021

    libstdc++: Use reserved name for attribute [PR101055]
    
    The no_unique_address attribute is not a reserved name until C++20, so
    to use it in C++11/14/17 modes we should use the __no_unique_address_
    form. We already use that form when using the attribute, but not in the
    __has_cpp_attribute check.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/101055
            * include/std/tuple: Use reserved form of attribute name.
            * testsuite/17_intro/headers/c++2011/all_attributes.cc: Add
            check for no_unique_address.
            * testsuite/17_intro/headers/c++2014/all_attributes.cc:
            Likewise.
            * testsuite/17_intro/headers/c++2017/all_attributes.cc:
            Likewise.

diff --git a/libstdc++-v3/include/std/tuple b/libstdc++-v3/include/std/tuple
index 3b771c50b25..2d562f8da77 100644
--- a/libstdc++-v3/include/std/tuple
+++ b/libstdc++-v3/include/std/tuple
@@ -73,7 +73,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 	   bool = __empty_not_final<_Head>::value>
     struct _Head_base;
 
-#if __has_cpp_attribute(no_unique_address)
+#if __has_cpp_attribute(__no_unique_address__)
   template<size_t _Idx, typename _Head>
     struct _Head_base<_Idx, _Head, true>
     {
diff --git a/libstdc++-v3/testsuite/17_intro/headers/c++2011/all_attributes.cc b/libstdc++-v3/testsuite/17_intro/headers/c++2011/all_attributes.cc
index c5c94ad7702..c38fc7d4d84 100644
--- a/libstdc++-v3/testsuite/17_intro/headers/c++2011/all_attributes.cc
+++ b/libstdc++-v3/testsuite/17_intro/headers/c++2011/all_attributes.cc
@@ -28,6 +28,7 @@
 # define deprecated 1
 # define visibility 1
 #endif
+#define no_unique_address 1
 #define packed 1
 #define pure 1
 // glibc's sysdeps/unix/sysv/linux/arm/sys/ucontext.h uses this on ARM.
diff --git a/libstdc++-v3/testsuite/17_intro/headers/c++2014/all_attributes.cc b/libstdc++-v3/testsuite/17_intro/headers/c++2014/all_attributes.cc
index c8f036219ff..65d273db19c 100644
--- a/libstdc++-v3/testsuite/17_intro/headers/c++2014/all_attributes.cc
+++ b/libstdc++-v3/testsuite/17_intro/headers/c++2014/all_attributes.cc
@@ -28,6 +28,7 @@
 # define deprecated 1
 # define visibility 1
 #endif
+#define no_unique_address 1
 #define packed 1
 #define pure 1
 // glibc's sysdeps/unix/sysv/linux/arm/sys/ucontext.h uses this on ARM.
diff --git a/libstdc++-v3/testsuite/17_intro/headers/c++2017/all_attributes.cc b/libstdc++-v3/testsuite/17_intro/headers/c++2017/all_attributes.cc
index c4e38d6423a..811b3fe3613 100644
--- a/libstdc++-v3/testsuite/17_intro/headers/c++2017/all_attributes.cc
+++ b/libstdc++-v3/testsuite/17_intro/headers/c++2017/all_attributes.cc
@@ -26,6 +26,7 @@
 # define cold 1
 # define visibility 1
 #endif
+#define no_unique_address 1
 #define packed 1
 #define pure 1
 // glibc's sysdeps/unix/sysv/linux/arm/sys/ucontext.h uses this on ARM.