[gcc r8-10849] libstdc++: Fix errors from Library Fundamentals TS headers in C++11 [PR 98319]

[Jonathan Wakely <redi@gcc.gnu.org>]

https://gcc.gnu.org/g:c79725c7b21838e89105381ceff5af05b3609d21

commit r8-10849-gc79725c7b21838e89105381ceff5af05b3609d21
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Dec 16 13:37:17 2020 +0000

    libstdc++: Fix errors from Library Fundamentals TS headers in C++11 [PR 98319]
    
    Currently the <experimental/random>, <experimental/source_location> and
    <experimental/utility> headers can be included in C++98 and C++11 modes,
    but gives errors. With this change they can be included, but define
    nothing.
    
    libstdc++-v3/ChangeLog:
    
            PR libstdc++/98319
            * include/experimental/memory_resource: Add system_header pragma
            and only define contents for C++14 and later.
            * include/experimental/random: Only define contents for C++14
            and later.
            * include/experimental/source_location: Likewise.
            * include/experimental/utility: Likewise.
            * testsuite/experimental/feat-lib-fund.cc: Include all LFTS
            headers that are present. Allow test to run for all modes.
    
    (cherry picked from commit ab9bd93271061f436c10e35e261ecb73e2108ccc)

Diff:
---
 libstdc++-v3/include/experimental/memory_resource  |  8 +-
 libstdc++-v3/include/experimental/random           |  4 +-
 libstdc++-v3/include/experimental/source_location  |  4 +-
 libstdc++-v3/include/experimental/utility          |  4 +-
 .../testsuite/experimental/feat-lib-fund.cc        | 93 +++++++++-------------
 5 files changed, 51 insertions(+), 62 deletions(-)

diff --git a/libstdc++-v3/include/experimental/memory_resource b/libstdc++-v3/include/experimental/memory_resource
index 23653ee2fe8..29e53930a39 100644
--- a/libstdc++-v3/include/experimental/memory_resource
+++ b/libstdc++-v3/include/experimental/memory_resource
@@ -29,6 +29,10 @@
 #ifndef _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE
 #define _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE 1
 
+#pragma GCC system_header
+
+#if __cplusplus >= 201402L
+
 #include <memory>
 #include <new>
 #include <atomic>
@@ -403,5 +407,5 @@ namespace pmr {
 
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
-
-#endif
+#endif // C++14
+#endif // _GLIBCXX_EXPERIMENTAL_MEMORY_RESOURCE
diff --git a/libstdc++-v3/include/experimental/random b/libstdc++-v3/include/experimental/random
index deb7bd6b75c..a26b5f6cdce 100644
--- a/libstdc++-v3/include/experimental/random
+++ b/libstdc++-v3/include/experimental/random
@@ -29,6 +29,7 @@
 #ifndef _GLIBCXX_EXPERIMENTAL_RANDOM
 #define _GLIBCXX_EXPERIMENTAL_RANDOM 1
 
+#if __cplusplus >= 201402L
 #include <random>
 #include <experimental/bits/lfts_config.h>
 
@@ -77,4 +78,5 @@ inline namespace fundamentals_v2 {
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 
-#endif
+#endif // C++14
+#endif // _GLIBCXX_EXPERIMENTAL_RANDOM
diff --git a/libstdc++-v3/include/experimental/source_location b/libstdc++-v3/include/experimental/source_location
index 389eb816be1..988d23e12db 100644
--- a/libstdc++-v3/include/experimental/source_location
+++ b/libstdc++-v3/include/experimental/source_location
@@ -29,6 +29,7 @@
 #ifndef _GLIBCXX_EXPERIMENTAL_SRCLOC
 #define _GLIBCXX_EXPERIMENTAL_SRCLOC 1
 
+#if __cplusplus >= 201402L
 #include <cstdint>
 
 namespace std {
@@ -83,4 +84,5 @@ inline namespace fundamentals_v2 {
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 
-#endif
+#endif // C++14
+#endif // _GLIBCXX_EXPERIMENTAL_SRCLOC
diff --git a/libstdc++-v3/include/experimental/utility b/libstdc++-v3/include/experimental/utility
index 7e367196744..de3fe84a41b 100644
--- a/libstdc++-v3/include/experimental/utility
+++ b/libstdc++-v3/include/experimental/utility
@@ -29,6 +29,7 @@
 #ifndef _GLIBCXX_EXPERIMENTAL_UTILITY
 #define _GLIBCXX_EXPERIMENTAL_UTILITY 1
 
+#if __cplusplus >= 201402L
 #include <utility>
 #include <bits/uses_allocator.h>
 #include <experimental/bits/lfts_config.h>
@@ -46,4 +47,5 @@ inline namespace fundamentals_v2 {
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace std
 
-#endif
+#endif // C++14
+#endif // _GLIBCXX_EXPERIMENTAL_UTILITY
diff --git a/libstdc++-v3/testsuite/experimental/feat-lib-fund.cc b/libstdc++-v3/testsuite/experimental/feat-lib-fund.cc
index b0e6e289009..342edc5352d 100644
--- a/libstdc++-v3/testsuite/experimental/feat-lib-fund.cc
+++ b/libstdc++-v3/testsuite/experimental/feat-lib-fund.cc
@@ -1,57 +1,36 @@
-// { dg-do preprocess { target c++14 } }
-
-#if !__has_include(<experimental/tuple>)
-#  error "<experimental/tuple>"
-#endif
-
-#if !__has_include(<experimental/type_traits>)
-#  error "<experimental/type_traits>"
-#endif
-
-#if !__has_include(<experimental/ratio>)
-#  error "<experimental/ratio>"
-#endif
-
-#if !__has_include(<experimental/chrono>)
-#  error "<experimental/chrono>"
-#endif
-
-#if !__has_include(<experimental/system_error>)
-#  error "<experimental/system_error>"
-#endif
-
-#if !__has_include(<experimental/functional>)
-#  error "<experimental/functional>"
-#endif
-
-#if !__has_include(<experimental/optional>)
-#  error "<experimental/optional>"
-#endif
-
-#if !__has_include(<experimental/any>)
-#  error "<experimental/any>"
-#endif
-
-#if !__has_include(<experimental/string_view>)
-#  error "<experimental/string_view>"
-#endif
-
-//#if !__has_include(<experimental/memory>)
-//#  error "<experimental/memory>"
-//#endif
-
-//#if !__has_include(<experimental/memory_resource>)
-//#  error "<experimental/memory_resource>"
-//#endif
-
-//#if !__has_include(<experimental/future>)
-//#  error "<experimental/future>"
-//#endif
-
-#if !__has_include(<experimental/algorithm>)
-#  error "<experimental/algorithm>"
-#endif
-
-//#if !__has_include(<experimental/net>)
-//#  error "<experimental/net>"
-//#endif
+// { dg-do preprocess }
+
+// Include all the LFTS headers. This should work with any -std flag.
+
+#include <experimental/algorithm>
+#include <experimental/any>
+#include <experimental/array>
+#include <experimental/chrono>
+#include <experimental/deque>
+#include <experimental/forward_list>
+#include <experimental/functional>
+#if __has_include(<experimental/future>) // not supported as of GCC 11
+# include <experimental/future>
+#endif
+#include <experimental/iterator>
+#include <experimental/list>
+#include <experimental/map>
+#include <experimental/memory>
+#include <experimental/memory_resource>
+#include <experimental/numeric>
+#include <experimental/optional>
+#include <experimental/propagate_const>
+#include <experimental/random>
+#include <experimental/ratio>
+#include <experimental/regex>
+#include <experimental/set>
+#include <experimental/source_location>
+#include <experimental/string>
+#include <experimental/string_view>
+#include <experimental/system_error>
+#include <experimental/tuple>
+#include <experimental/type_traits>
+#include <experimental/unordered_map>
+#include <experimental/unordered_set>
+#include <experimental/utility>
+#include <experimental/vector>