libstdc++: Mark headers that must be hosted as such [PR103626]

PR libstdc++/103626 - _GLIBCXX_HOSTED should respect -ffreestanding

Co-authored-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	PR libstdc++/103626
	* include/Makefile.am: Add new header.
	* include/Makefile.in: Regenerate.
	* include/bits/requires_hosted.h: New header.
	* include/experimental/algorithm: Include
	<bits/requires_hosted.h>.
	* include/experimental/any: Likewise.
	* include/experimental/array: Likewise.
	* include/experimental/buffer: Likewise.
	* include/experimental/chrono: Likewise.
	* include/experimental/deque: Likewise.
	* include/experimental/executor: Likewise.
	* include/experimental/filesystem: Likewise.
	* include/experimental/forward_list: Likewise.
	* include/experimental/functional: Likewise.
	* include/experimental/internet: Likewise.
	* include/experimental/io_context: Likewise.
	* include/experimental/iterator: Likewise.
	* include/experimental/list: Likewise.
	* include/experimental/map: Likewise.
	* include/experimental/memory: Likewise.
	* include/experimental/memory_resource: Likewise.
	* include/experimental/net: Likewise.
	* include/experimental/netfwd: Likewise.
	* include/experimental/numeric: Likewise.
	* include/experimental/optional: Likewise.
	* include/experimental/propagate_const: Likewise.
	* include/experimental/random: Likewise.
	* include/experimental/ratio: Likewise.
	* include/experimental/regex: Likewise.
	* include/experimental/scope: Likewise.
	* include/experimental/set: Likewise.
	* include/experimental/simd: Likewise.
	* include/experimental/socket: Likewise.
	* include/experimental/source_location: Likewise.
	* include/experimental/string: Likewise.
	* include/experimental/string_view: Likewise.
	* include/experimental/system_error: Likewise.
	* include/experimental/timer: Likewise.
	* include/experimental/tuple: Likewise.
	* include/experimental/unordered_map: Likewise.
	* include/experimental/unordered_set: Likewise.
	* include/experimental/utility: Likewise.
	* include/experimental/vector: Likewise.
	* include/std/barrier: Likewise.
	* include/std/chrono: Likewise.
	* include/std/condition_variable: Likewise.
	* include/std/deque: Likewise.
	* include/std/execution: Likewise.
	* include/std/filesystem: Likewise.
	* include/std/forward_list: Likewise.
	* include/std/fstream: Likewise.
	* include/std/future: Likewise.
	* include/std/iomanip: Likewise.
	* include/std/ios: Likewise.
	* include/std/iosfwd: Likewise.
	* include/std/iostream: Likewise.
	* include/std/istream: Likewise.
	* include/std/latch: Likewise.
	* include/std/list: Likewise.
	* include/std/locale: Likewise.
	* include/std/map: Likewise.
	* include/std/memory_resource: Likewise.
	* include/std/mutex: Likewise.
	* include/std/ostream: Likewise.
	* include/std/queue: Likewise.
	* include/std/random: Likewise.
	* include/std/regex: Likewise.
	* include/std/semaphore: Likewise.
	* include/std/set: Likewise.
	* include/std/shared_mutex: Likewise.
	* include/std/spanstream: Likewise.
	* include/std/sstream: Likewise.
	* include/std/stack: Likewise.
	* include/std/stacktrace: Likewise.
	* include/std/stop_token: Likewise.
	* include/std/streambuf: Likewise.
	* include/std/string: Likewise.
	* include/std/syncstream: Likewise.
	* include/std/system_error: Likewise.
	* include/std/thread: Likewise.
	* include/std/unordered_map: Likewise.
	* include/std/unordered_set: Likewise.
	* include/std/valarray: Likewise.
	* include/std/vector: Likewise.
	* include/tr1/array: Likewise.
	* include/tr1/ccomplex: Likewise.
	* include/tr1/cctype: Likewise.
	* include/tr1/cfenv: Likewise.
	* include/tr1/cfloat: Likewise.
	* include/tr1/cinttypes: Likewise.
	* include/tr1/climits: Likewise.
	* include/tr1/cmath: Likewise.
	* include/tr1/complex: Likewise.
	* include/tr1/complex.h: Likewise.
	* include/tr1/cstdarg: Likewise.
	* include/tr1/cstdbool: Likewise.
	* include/tr1/cstdint: Likewise.
	* include/tr1/cstdio: Likewise.
	* include/tr1/cstdlib: Likewise.
	* include/tr1/ctgmath: Likewise.
	* include/tr1/ctime: Likewise.
	* include/tr1/ctype.h: Likewise.
	* include/tr1/cwchar: Likewise.
	* include/tr1/cwctype: Likewise.
	* include/tr1/fenv.h: Likewise.
	* include/tr1/float.h: Likewise.
	* include/tr1/functional: Likewise.
	* include/tr1/inttypes.h: Likewise.
	* include/tr1/limits.h: Likewise.
	* include/tr1/math.h: Likewise.
	* include/tr1/memory: Likewise.
	* include/tr1/random: Likewise.
	* include/tr1/regex: Likewise.
	* include/tr1/stdarg.h: Likewise.
	* include/tr1/stdbool.h: Likewise.
	* include/tr1/stdint.h: Likewise.
	* include/tr1/stdio.h: Likewise.
	* include/tr1/stdlib.h: Likewise.
	* include/tr1/tgmath.h: Likewise.
	* include/tr1/tuple: Likewise.
	* include/tr1/type_traits: Likewise.
	* include/tr1/unordered_map: Likewise.
	* include/tr1/unordered_set: Likewise.
	* include/tr1/utility: Likewise.
	* include/tr1/wchar.h: Likewise.
	* include/tr1/wctype.h: Likewise.
	* include/c_global/cmath: Likewise.
	* include/ext/algorithm: Include <bits/requires_hosted.h>.
	* include/ext/bitmap_allocator.h: Likewise.
	* include/ext/cmath: Likewise.
	* include/ext/codecvt_specializations.h: Likewise.
	* include/ext/debug_allocator.h: Likewise.
	* include/ext/enc_filebuf.h: Likewise.
	* include/ext/extptr_allocator.h: Likewise.
	* include/ext/functional: Likewise.
	* include/ext/malloc_allocator.h: Likewise.
	* include/ext/memory: Likewise.
	* include/ext/mt_allocator.h: Likewise.
	* include/ext/new_allocator.h: Likewise.
	* include/ext/numeric: Likewise.
	* include/ext/pod_char_traits.h: Likewise.
	* include/ext/pool_allocator.h: Likewise.
	* include/ext/random: Likewise.
	* include/ext/random.tcc: Likewise.
	* include/ext/rb_tree: Likewise.
	* include/ext/rc_string_base.h: Likewise.
	* include/ext/rope: Likewise.
	* include/ext/ropeimpl.h: Likewise.
	* include/ext/slist: Likewise.
	* include/ext/sso_string_base.h: Likewise.
	* include/ext/stdio_filebuf.h: Likewise.
	* include/ext/stdio_sync_filebuf.h: Likewise.
	* include/ext/string_conversions.h: Likewise.
	* include/ext/throw_allocator.h: Likewise.
	* include/ext/vstring.h: Likewise.
	* include/ext/vstring.tcc: Likewise.
	* include/ext/vstring_fwd.h: Likewise.
	* include/ext/vstring_util.h: Likewise.
	* include/std/charconv: Likewise.
	(__cpp_lib_to_chars): Do not define for freestanding.
	* include/std/version: Adjust which macros get defined in
	freestanding.
	* include/ext/pointer.h [!_GLIBCXX_HOSTED]: Omit iostream
	functionality from freestanding.
	* include/std/algorithm [!_GLIBCXX_HOSTED]: Omit PSTL algos.
	* include/std/memory [!_GLIBCXX_HOSTED]: Omit
	<bits/stl_tempbuf.h> in freestanding
	* include/bits/algorithmfwd.h [!_GLIBCXX_HOSTED]: Omit leftover
	random_shuffle and stable_partition definition.
	* include/bits/stl_algo.h [!_GLIBCXX_HOSTED]: Omit
	random_shuffle and stable_partition from freestanding.
	* include/bits/ranges_algo.h [!_GLIBCXX_HOSTED]: Omit
	stable_partition from freestanding.
	* include/bits/concept_check.h: Remove needless HOSTED check.
	* include/std/iterator: Include <bits/ranges_base.h>.
	* include/std/numeric (__cpp_lib_parallel_algorithms): Do not
	define for freestanding.
	* include/std/functional (__cpp_lib_boyer_moore_searcher):
	Likewise.
	* testsuite/lib/prune.exp: Match error for hosted-only libstdc++
	tests.

32 files changed, 68 insertions, 1 deletions

diff --git a/libstdc++-v3/include/ext/algorithm b/libstdc++-v3/include/ext/algorithm
index f5eced6..65122da 100644
--- a/libstdc++-v3/include/ext/algorithm
+++ b/libstdc++-v3/include/ext/algorithm
@@ -58,6 +58,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <algorithm>
 
 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
diff --git a/libstdc++-v3/include/ext/bitmap_allocator.h b/libstdc++-v3/include/ext/bitmap_allocator.h
index 033f132..80b8fa7 100644
--- a/libstdc++-v3/include/ext/bitmap_allocator.h
+++ b/libstdc++-v3/include/ext/bitmap_allocator.h
@@ -29,6 +29,8 @@
 #ifndef _BITMAP_ALLOCATOR_H
 #define _BITMAP_ALLOCATOR_H 1
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <utility> // For std::pair.
 #include <bits/functexcept.h> // For __throw_bad_alloc().
 #include <bits/stl_function.h> // For greater_equal, and less_equal.
diff --git a/libstdc++-v3/include/ext/cmath b/libstdc++-v3/include/ext/cmath
index 2291969..2ebad8b 100644
--- a/libstdc++-v3/include/ext/cmath
+++ b/libstdc++-v3/include/ext/cmath
@@ -31,6 +31,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #if __cplusplus < 201103L
 # include <bits/c++0x_warning.h>
 #else
diff --git a/libstdc++-v3/include/ext/codecvt_specializations.h b/libstdc++-v3/include/ext/codecvt_specializations.h
index 51b638d..7f733e6 100644
--- a/libstdc++-v3/include/ext/codecvt_specializations.h
+++ b/libstdc++-v3/include/ext/codecvt_specializations.h
@@ -35,6 +35,8 @@
 #ifndef _EXT_CODECVT_SPECIALIZATIONS_H
 #define _EXT_CODECVT_SPECIALIZATIONS_H 1
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <bits/c++config.h>
 #include <locale>
 #include <iconv.h>
diff --git a/libstdc++-v3/include/ext/debug_allocator.h b/libstdc++-v3/include/ext/debug_allocator.h
index 3490dca..06c15fb 100644
--- a/libstdc++-v3/include/ext/debug_allocator.h
+++ b/libstdc++-v3/include/ext/debug_allocator.h
@@ -42,6 +42,8 @@
 #ifndef _DEBUG_ALLOCATOR_H
 #define _DEBUG_ALLOCATOR_H 1
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <stdexcept>
 #include <bits/functexcept.h>
 #include <ext/alloc_traits.h>
diff --git a/libstdc++-v3/include/ext/enc_filebuf.h b/libstdc++-v3/include/ext/enc_filebuf.h
index 12869a8..fc3d9a8 100644
--- a/libstdc++-v3/include/ext/enc_filebuf.h
+++ b/libstdc++-v3/include/ext/enc_filebuf.h
@@ -29,6 +29,8 @@
 #ifndef _EXT_ENC_FILEBUF_H
 #define _EXT_ENC_FILEBUF_H 1
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <fstream>
 #include <locale>
 #include <ext/codecvt_specializations.h>
diff --git a/libstdc++-v3/include/ext/extptr_allocator.h b/libstdc++-v3/include/ext/extptr_allocator.h
index 20f746e..ad538c7 100644
--- a/libstdc++-v3/include/ext/extptr_allocator.h
+++ b/libstdc++-v3/include/ext/extptr_allocator.h
@@ -36,6 +36,8 @@
 #ifndef _EXTPTR_ALLOCATOR_H
 #define _EXTPTR_ALLOCATOR_H 1
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <memory>
 #include <ext/numeric_traits.h>
 #include <ext/pointer.h>
diff --git a/libstdc++-v3/include/ext/functional b/libstdc++-v3/include/ext/functional
index 19cd8d5..9cf864d 100644
--- a/libstdc++-v3/include/ext/functional
+++ b/libstdc++-v3/include/ext/functional
@@ -58,6 +58,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <functional>
 
 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
diff --git a/libstdc++-v3/include/ext/malloc_allocator.h b/libstdc++-v3/include/ext/malloc_allocator.h
index 82b3f0a..6323ed9 100644
--- a/libstdc++-v3/include/ext/malloc_allocator.h
+++ b/libstdc++-v3/include/ext/malloc_allocator.h
@@ -29,6 +29,8 @@
 #ifndef _MALLOC_ALLOCATOR_H
 #define _MALLOC_ALLOCATOR_H 1
 
+#include <bits/requires_hosted.h> // malloc
+
 #include <cstdlib>
 #include <cstddef>
 #include <new>
diff --git a/libstdc++-v3/include/ext/memory b/libstdc++-v3/include/ext/memory
index 105952a..9e0082b 100644
--- a/libstdc++-v3/include/ext/memory
+++ b/libstdc++-v3/include/ext/memory
@@ -58,6 +58,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <memory>
 #include <bits/stl_tempbuf.h>
 
diff --git a/libstdc++-v3/include/ext/mt_allocator.h b/libstdc++-v3/include/ext/mt_allocator.h
index 393d6eb0a..49743e4 100644
--- a/libstdc++-v3/include/ext/mt_allocator.h
+++ b/libstdc++-v3/include/ext/mt_allocator.h
@@ -29,6 +29,8 @@
 #ifndef _MT_ALLOCATOR_H
 #define _MT_ALLOCATOR_H 1
 
+#include <bits/requires_hosted.h> // getenv
+
 #include <new>
 #include <cstdlib>
 #include <bits/functexcept.h>
diff --git a/libstdc++-v3/include/ext/new_allocator.h b/libstdc++-v3/include/ext/new_allocator.h
index 96e6523..db8895f 100644
--- a/libstdc++-v3/include/ext/new_allocator.h
+++ b/libstdc++-v3/include/ext/new_allocator.h
@@ -29,6 +29,8 @@
 #ifndef _NEW_ALLOCATOR_H
 #define _NEW_ALLOCATOR_H 1
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <bits/new_allocator.h>
 
 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
diff --git a/libstdc++-v3/include/ext/numeric b/libstdc++-v3/include/ext/numeric
index 0b2c4ee..1d9f4f4 100644
--- a/libstdc++-v3/include/ext/numeric
+++ b/libstdc++-v3/include/ext/numeric
@@ -58,6 +58,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <bits/concept_check.h>
 #include <numeric>
 
diff --git a/libstdc++-v3/include/ext/pod_char_traits.h b/libstdc++-v3/include/ext/pod_char_traits.h
index fa0f5b6..95d90f3 100644
--- a/libstdc++-v3/include/ext/pod_char_traits.h
+++ b/libstdc++-v3/include/ext/pod_char_traits.h
@@ -34,6 +34,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <string>
 
 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
diff --git a/libstdc++-v3/include/ext/pointer.h b/libstdc++-v3/include/ext/pointer.h
index 04804f0..48b7684 100644
--- a/libstdc++-v3/include/ext/pointer.h
+++ b/libstdc++-v3/include/ext/pointer.h
@@ -38,7 +38,10 @@
 
 #pragma GCC system_header
 
-#include <iosfwd>
+#if _GLIBCXX_HOSTED
+#  include <iosfwd>
+#endif
+
 #include <bits/stl_iterator_base_types.h>
 #include <ext/cast.h>
 #include <ext/type_traits.h>
@@ -559,11 +562,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
                const _Pointer_adapter<_Tp>& __rhs)
     { return !(__lhs._Tp::operator<(__rhs)); }
 
+#if _GLIBCXX_HOSTED
   template<typename _CharT, typename _Traits, typename _StoreT>
     inline std::basic_ostream<_CharT, _Traits>&
     operator<<(std::basic_ostream<_CharT, _Traits>& __os, 
                const _Pointer_adapter<_StoreT>& __p)
     { return (__os << __p.get()); }
+#endif // HOSTED
 
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
diff --git a/libstdc++-v3/include/ext/pool_allocator.h b/libstdc++-v3/include/ext/pool_allocator.h
index 8d0f089..f04a88c 100644
--- a/libstdc++-v3/include/ext/pool_allocator.h
+++ b/libstdc++-v3/include/ext/pool_allocator.h
@@ -42,6 +42,8 @@
 #ifndef _POOL_ALLOCATOR_H
 #define _POOL_ALLOCATOR_H 1
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <bits/c++config.h>
 #include <cstdlib>
 #include <new>
diff --git a/libstdc++-v3/include/ext/random b/libstdc++-v3/include/ext/random
index 50505b8..4cc0e25 100644
--- a/libstdc++-v3/include/ext/random
+++ b/libstdc++-v3/include/ext/random
@@ -31,6 +31,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #if __cplusplus < 201103L
 # include <bits/c++0x_warning.h>
 #else
diff --git a/libstdc++-v3/include/ext/random.tcc b/libstdc++-v3/include/ext/random.tcc
index 71ceea8..7274e0d 100644
--- a/libstdc++-v3/include/ext/random.tcc
+++ b/libstdc++-v3/include/ext/random.tcc
@@ -32,6 +32,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
diff --git a/libstdc++-v3/include/ext/rb_tree b/libstdc++-v3/include/ext/rb_tree
index b61c45b..dd685fb 100644
--- a/libstdc++-v3/include/ext/rb_tree
+++ b/libstdc++-v3/include/ext/rb_tree
@@ -58,6 +58,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <bits/stl_tree.h>
 
 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
diff --git a/libstdc++-v3/include/ext/rc_string_base.h b/libstdc++-v3/include/ext/rc_string_base.h
index f196d884..21ccfc2 100644
--- a/libstdc++-v3/include/ext/rc_string_base.h
+++ b/libstdc++-v3/include/ext/rc_string_base.h
@@ -30,6 +30,8 @@
 #ifndef _RC_STRING_BASE_H
 #define _RC_STRING_BASE_H 1
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <ext/atomicity.h>
 #include <ext/alloc_traits.h>
 #include <bits/stl_iterator_base_funcs.h>
diff --git a/libstdc++-v3/include/ext/rope b/libstdc++-v3/include/ext/rope
index f8af374..a5a821e 100644
--- a/libstdc++-v3/include/ext/rope
+++ b/libstdc++-v3/include/ext/rope
@@ -45,6 +45,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <algorithm>
 #include <iosfwd>
 #include <bits/stl_construct.h>
diff --git a/libstdc++-v3/include/ext/ropeimpl.h b/libstdc++-v3/include/ext/ropeimpl.h
index 27cb738..fe35d91 100644
--- a/libstdc++-v3/include/ext/ropeimpl.h
+++ b/libstdc++-v3/include/ext/ropeimpl.h
@@ -1227,6 +1227,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 		__result = _S_concat(__forest[__i], __result);
 		__forest[__i]->_M_unref_nonnil();
 #if !defined(__GC) && __cpp_exceptions
+
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
 		__forest[__i] = 0;
 #endif
 	      }
diff --git a/libstdc++-v3/include/ext/slist b/libstdc++-v3/include/ext/slist
index 7b6f882..f2b5109 100644
--- a/libstdc++-v3/include/ext/slist
+++ b/libstdc++-v3/include/ext/slist
@@ -44,6 +44,8 @@
 #ifndef _SLIST
 #define _SLIST 1
 
+#include <bits/requires_hosted.h> // std::allocator
+
 #include <algorithm>
 #include <bits/allocator.h>
 #include <bits/stl_construct.h>
diff --git a/libstdc++-v3/include/ext/sso_string_base.h b/libstdc++-v3/include/ext/sso_string_base.h
index f2209e7..db5dc43 100644
--- a/libstdc++-v3/include/ext/sso_string_base.h
+++ b/libstdc++-v3/include/ext/sso_string_base.h
@@ -30,6 +30,8 @@
 #ifndef _SSO_STRING_BASE_H
 #define _SSO_STRING_BASE_H 1
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
diff --git a/libstdc++-v3/include/ext/stdio_filebuf.h b/libstdc++-v3/include/ext/stdio_filebuf.h
index 878839b..0e83e35 100644
--- a/libstdc++-v3/include/ext/stdio_filebuf.h
+++ b/libstdc++-v3/include/ext/stdio_filebuf.h
@@ -31,6 +31,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <fstream>
 
 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
diff --git a/libstdc++-v3/include/ext/stdio_sync_filebuf.h b/libstdc++-v3/include/ext/stdio_sync_filebuf.h
index 49437c9..8f51ae2 100644
--- a/libstdc++-v3/include/ext/stdio_sync_filebuf.h
+++ b/libstdc++-v3/include/ext/stdio_sync_filebuf.h
@@ -31,6 +31,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <streambuf>
 #include <cstdio>
 #include <bits/c++io.h>  // For __c_file
diff --git a/libstdc++-v3/include/ext/string_conversions.h b/libstdc++-v3/include/ext/string_conversions.h
index fc03974..a4648a9 100644
--- a/libstdc++-v3/include/ext/string_conversions.h
+++ b/libstdc++-v3/include/ext/string_conversions.h
@@ -31,6 +31,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #if __cplusplus < 201103L
 # include <bits/c++0x_warning.h>
 #else
diff --git a/libstdc++-v3/include/ext/throw_allocator.h b/libstdc++-v3/include/ext/throw_allocator.h
index 220f5f5..a1b57e7 100644
--- a/libstdc++-v3/include/ext/throw_allocator.h
+++ b/libstdc++-v3/include/ext/throw_allocator.h
@@ -46,6 +46,8 @@
 #ifndef _THROW_ALLOCATOR_H
 #define _THROW_ALLOCATOR_H 1
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <cmath>
 #include <ctime>
 #include <map>
diff --git a/libstdc++-v3/include/ext/vstring.h b/libstdc++-v3/include/ext/vstring.h
index 47cbabf..f0a12d6 100644
--- a/libstdc++-v3/include/ext/vstring.h
+++ b/libstdc++-v3/include/ext/vstring.h
@@ -31,6 +31,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #if __cplusplus >= 201103L
 #include <initializer_list>
 #endif
diff --git a/libstdc++-v3/include/ext/vstring.tcc b/libstdc++-v3/include/ext/vstring.tcc
index 0776fdc..18e4bbb 100644
--- a/libstdc++-v3/include/ext/vstring.tcc
+++ b/libstdc++-v3/include/ext/vstring.tcc
@@ -32,6 +32,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <bits/cxxabi_forced.h>
 
 namespace __gnu_cxx _GLIBCXX_VISIBILITY(default)
diff --git a/libstdc++-v3/include/ext/vstring_fwd.h b/libstdc++-v3/include/ext/vstring_fwd.h
index c787e95..121492b 100644
--- a/libstdc++-v3/include/ext/vstring_fwd.h
+++ b/libstdc++-v3/include/ext/vstring_fwd.h
@@ -32,6 +32,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <bits/c++config.h>
 #include <bits/char_traits.h>
 #include <bits/allocator.h>
diff --git a/libstdc++-v3/include/ext/vstring_util.h b/libstdc++-v3/include/ext/vstring_util.h
index 713c697..4e58a71 100644
--- a/libstdc++-v3/include/ext/vstring_util.h
+++ b/libstdc++-v3/include/ext/vstring_util.h
@@ -32,6 +32,8 @@
 
 #pragma GCC system_header
 
+#include <bits/requires_hosted.h> // GNU extensions are currently omitted
+
 #include <ext/vstring_fwd.h>
 #include <debug/debug.h>
 #include <bits/stl_function.h>  // For less