From 08663e439fcfc0c29b9bd8298bf8a113b2ee269a Mon Sep 17 00:00:00 2001
From: Alex Guteniev <gutenev@gmail.com>
Date: Mon, 14 Aug 2023 19:18:29 +0300
Subject: [PATCH] Implement `atomic_flag` formatter

Copy-pasta from @wangzw PR
---
 include/fmt/std.h | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/include/fmt/std.h b/include/fmt/std.h
index 5cfe1d87..2d3faf05 100644
--- a/include/fmt/std.h
+++ b/include/fmt/std.h
@@ -448,5 +448,19 @@ struct formatter<std::atomic<T>, Char,
   }
 };
 
+#if defined(__cpp_lib_atomic_flag_test) && __cpp_lib_atomic_flag_test >= 201907L
+FMT_EXPORT
+template <typename Char>
+struct formatter<std::atomic_flag, Char,
+                 enable_if_t<is_formattable<bool, Char>::value>>
+    : formatter<bool, Char> {
+  template <typename FormatContext>
+  auto format(const std::atomic_flag& v, FormatContext& ctx) const
+      -> decltype(ctx.out()) {
+    return formatter<bool, Char>::format(v.test(), ctx);
+  }
+};
+#endif // defined(__cpp_lib_atomic_flag_test) && __cpp_lib_atomic_flag_test >= 201907L
+
 FMT_END_NAMESPACE
 #endif  // FMT_STD_H_