Logging std::filesystem::path without explicit conversion to std::string (#168)

Author: SergiusTheBest

include/plog/Record.h

@@ -11,6 +11,24 @@ namespace plog
 {
     namespace detail
     {
+        namespace meta
+        {
+            template<class T>
+            inline T& declval()
+            {
+#ifdef __INTEL_COMPILER
+#    pragma warning(suppress: 327) // NULL reference is not allowed
+#endif
+                return *reinterpret_cast<T*>(0);
+            }
+
+            template<bool B, class T = void>
+            struct enableIf {};
+
+            template<class T>
+            struct enableIf<true, T> { typedef T type; };
+        }
+
         //////////////////////////////////////////////////////////////////////////
         // Stream output operators as free functions
 
@@ -27,11 +45,22 @@ namespace plog
 #endif
         }
 
+        inline void operator<<(util::nostringstream& stream, char* data)
+        {
+            plog::detail::operator<<(stream, const_cast<const char*>(data));
+        }
+
         inline void operator<<(util::nostringstream& stream, const std::string& data)
         {
             plog::detail::operator<<(stream, data.c_str());
         }
 
+        template<typename T>
+        inline typename meta::enableIf<!!sizeof(static_cast<std::basic_string<util::nchar> >(meta::declval<T>())), void>::type operator<<(util::nostringstream& stream, const T& data)
+        {
+            plog::detail::operator<<(stream, static_cast<std::basic_string<util::nchar> >(data));
+        }
+
 #if PLOG_ENABLE_WCHAR_INPUT
         inline void operator<<(util::nostringstream& stream, const wchar_t* data)
         {
@@ -44,6 +73,11 @@ namespace plog
 #   endif
         }
 
+        inline void operator<<(util::nostringstream& stream, wchar_t* data)
+        {
+            plog::detail::operator<<(stream, const_cast<const wchar_t*>(data));
+        }
+
         inline void operator<<(util::nostringstream& stream, const std::wstring& data)
         {
             plog::detail::operator<<(stream, data.c_str());
@@ -67,10 +101,7 @@ namespace plog
             template <class T, class Stream>
             struct isStreamable
             {
-#ifdef __INTEL_COMPILER
-#    pragma warning(suppress: 327) // NULL reference is not allowed
-#endif
-                enum { value = sizeof(operator<<(*reinterpret_cast<Stream*>(0), *reinterpret_cast<const T*>(0))) != sizeof(char) };
+                enum { value = sizeof(operator<<(meta::declval<Stream>(), meta::declval<const T>())) != sizeof(char) };
             };
 
             template <class Stream>
@@ -90,12 +121,6 @@ namespace plog
             {
                 enum { value = false };
             };
-
-            template<bool B, class T = void>
-            struct enableIf {};
-
-            template<class T>
-            struct enableIf<true, T> { typedef T type; };
         }
 
         template<class T>

samples/CMakeLists.txt

@@ -55,6 +55,7 @@ add_subdirectory(Library)
 add_subdirectory(MultiAppender)
 add_subdirectory(MultiInstance)
 add_subdirectory(ObjectiveC)
+add_subdirectory(Path)
 add_subdirectory(Performance)
 add_subdirectory(SetFileName)
 add_subdirectory(Shared)

samples/Path/CMakeLists.txt

@@ -0,0 +1,11 @@
+if (CMAKE_VERSION VERSION_GREATER 3.1.0)
+    if ((CMAKE_COMPILER_IS_GNUCC AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 7.0) OR (MSVC AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 19.10))
+        add_executable(Path Main.cpp)
+        target_link_libraries(Path plog)
+        set_target_properties(Path PROPERTIES FOLDER Samples)
+        set_target_properties(Path PROPERTIES CXX_STANDARD 17)
+        if (CMAKE_COMPILER_IS_GNUCC AND CMAKE_CXX_COMPILER_VERSION VERSION_GREATER 7.0 AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 9.0)
+            target_link_libraries(Path stdc++fs)
+        endif()
+    endif()
+endif()

samples/Path/Main.cpp

@@ -0,0 +1,22 @@
+//
+// Path - a test sample to check that std::filesystem::path can be logged.
+//
+
+#include <plog/Log.h>
+
+#if __has_include(<filesystem>)
+    #include <filesystem>
+    namespace fs = std::filesystem;
+#else
+    #include <experimental/filesystem>
+    namespace fs = std::experimental::filesystem;
+#endif
+
+int main()
+{
+    plog::init(plog::debug, "Path.txt");
+
+    PLOGI << "Current path: " << fs::current_path();
+
+    return 0;
+}