kapi: finish documentation

1 files changed, 18 insertions, 3 deletions

diff --git a/kapi/src/cio.cpp b/kapi/src/cio.cpp
index 210e58e..66493b6 100644
--- a/kapi/src/cio.cpp
+++ b/kapi/src/cio.cpp
@@ -1,14 +1,29 @@
 #include "kapi/cio.hpp"
 
 #include <optional>
+#include <string_view>
 #include <utility>
 
 namespace teachos::cio
 {
+  namespace
+  {
+    struct null_device final : public output_device
+    {
+      null_device static instance;
+
+      auto write(std::string_view) -> void override {}
+      auto writeln(std::string_view) -> void override {}
+
+      auto write_error(std::string_view) -> void override {}
+      auto writeln_error(std::string_view) -> void override {}
+    };
+
+    constinit null_device null_device::instance;
+  }  // namespace
+
   // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-  auto constinit null_device = output_device{};
-  // NOLINTNEXTLINE(cppcoreguidelines-avoid-non-const-global-variables)
-  auto constinit active_device = &null_device;
+  constinit auto active_device = static_cast<output_device *>(&null_device::instance);
 
   auto set_output_device(output_device & device) -> std::optional<output_device *>
   {