From 71988274865bf049c7705ce33350661b75f0af74 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Thu, 26 Nov 2020 21:54:46 +0000
Subject: [PATCH] libstdc++: Only define std::latch if atomic waiting is
 available

libstdc++-v3/ChangeLog:

	* include/std/latch: Depend on _GLIBCXX_HAS_GTHREADS and
	_GLIBCXX_HAVE_LINUX_FUTEX.
	* include/std/version (__cpp_lib_latch): Define conditionally.
---
 libstdc++-v3/include/std/latch   | 7 +++++--
 libstdc++-v3/include/std/version | 6 ++++--
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/libstdc++-v3/include/std/latch b/libstdc++-v3/include/std/latch
index 9d9c880a88b..3af295b4eb4 100644
--- a/libstdc++-v3/include/std/latch
+++ b/libstdc++-v3/include/std/latch
@@ -27,20 +27,22 @@
  */
 
 #ifndef _GLIBCXX_LATCH
-#define _GLIBCXX_LATCH
+#define _GLIBCXX_LATCH 1
 
 #pragma GCC system_header
 
 #if __cplusplus > 201703L
-#define __cpp_lib_latch 201907L
 
 #include <bits/atomic_base.h>
 #include <ext/numeric_traits.h>
 
+#if defined _GLIBCXX_HAS_GTHREADS || _GLIBCXX_HAVE_LINUX_FUTEX
 namespace std _GLIBCXX_VISIBILITY(default)
 {
 _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
+#define __cpp_lib_latch 201907L
+
   class latch
   {
   public:
@@ -87,5 +89,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   };
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
+#endif // GTHREADS || LINUX_FUTEX
 #endif // __cplusplus > 201703L
 #endif // _GLIBCXX_LATCH
diff --git a/libstdc++-v3/include/std/version b/libstdc++-v3/include/std/version
index cf0454dbaf8..0f2da8a5ddd 100644
--- a/libstdc++-v3/include/std/version
+++ b/libstdc++-v3/include/std/version
@@ -216,7 +216,9 @@
 #ifdef _GLIBCXX_HAS_GTHREADS
 # define __cpp_lib_jthread 201911L
 #endif
-#define __cpp_lib_latch 201907L
+#if defined _GLIBCXX_HAS_GTHREADS || defined _GLIBCXX_HAVE_LINUX_FUTEX
+# define __cpp_lib_latch 201907L
+#endif
 #define __cpp_lib_list_remove_return_type 201806L
 #if __cpp_lib_concepts
 # define __cpp_lib_make_obj_using_allocator 201811L
@@ -226,7 +228,7 @@
 #if __cpp_lib_concepts
 # define __cpp_lib_ranges 201911L
 #endif
-#if defined _GLIBCXX_HAS_GTHREADS || _GLIBCXX_HAVE_LINUX_FUTEX
+#if defined _GLIBCXX_HAS_GTHREADS || defined _GLIBCXX_HAVE_LINUX_FUTEX
 # define __cpp_lib_semaphore 201907L
 #endif
 #define __cpp_lib_shift 201806L
-- 
2.30.2