atomic_flag formatting (#3594)

fmtlib · Aug 25, 2023 · 9b74160 · 9b74160
1 parent a21690b
commit 9b74160
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diff --git a/include/fmt/std.h b/include/fmt/std.h
@@ -448,5 +448,18 @@ struct formatter<std::atomic<T>, Char,
   }
 };
 
+#ifdef __cpp_lib_atomic_flag_test
+FMT_EXPORT
+template <typename Char>
+struct formatter<std::atomic_flag, Char>
+    : 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 // __cpp_lib_atomic_flag_test
+
 FMT_END_NAMESPACE
 #endif  // FMT_STD_H_
diff --git a/test/std-test.cc b/test/std-test.cc
@@ -244,3 +244,14 @@ TEST(std_test, format_atomic) {
   const std::atomic<bool> cb(true);
   EXPECT_EQ(fmt::format("{}", cb), "true");
 }
+
+#ifdef __cpp_lib_atomic_flag_test
+TEST(std_test, format_atomic_flag) {
+  std::atomic_flag f = ATOMIC_FLAG_INIT;
+  (void) f.test_and_set();
+  EXPECT_EQ(fmt::format("{}", f), "true");
+
+  const std::atomic_flag cf = ATOMIC_FLAG_INIT;
+  EXPECT_EQ(fmt::format("{}", cf), "false");
+}
+#endif // __cpp_lib_atomic_flag_test