diff --git a/doc/src/io_helper.dox b/doc/src/io_helper.dox
index 02d72b5..806e2e8 100644
--- a/doc/src/io_helper.dox
+++ b/doc/src/io_helper.dox
@@ -3,7 +3,7 @@ namespace YYCC::IOHelper {
 
 \page io_helper IO Helper
 
-YYCC::IOHelper currently only has one function and one macro.
+Actually, YYCC::IOHelper includes functions which can not be placed in other place.
 
 \section io_helper__ptr_pri_padding Pointer Print Padding
 
@@ -25,6 +25,11 @@ std::printf(stdout, "Raw Pointer 0x%" PRI_XPTR_LEFT_PADDING PRIXPTR, raw_ptr);
 
 Note \c PRIXPTR is defined by standard library for formatting pointer as hexadecimal style.
 
+\section io_helper__smart_file Smart FILE Pointer
+
+#SmartStdFile use \c std::unique_ptr with custom deleter to implement smart \c FILE*.
+It is useful in the cases that you want to automatically free opened file when leaving corresponding scope.
+
 \section io_helper__utf8_fopen UTF8 fopen
 
 In Windows, standard \c std::fopen can not handle UTF8 file name in common environment.
diff --git a/src/ConfigManager.cpp b/src/ConfigManager.cpp
index 51f26cb..407285c 100644
--- a/src/ConfigManager.cpp
+++ b/src/ConfigManager.cpp
@@ -49,7 +49,7 @@ namespace YYCC::ConfigManager {
 		Reset();
 
 		// get file handle
-		auto fs = this->GetFileHandle(YYCC_U8("rb"));
+		IOHelper::SmartStdFile fs(IOHelper::UTF8FOpen(m_CfgFilePath.c_str(), YYCC_U8("rb")));
 		if (fs.get() == nullptr) {
 			// if we fail to get, it means that we do not have corresponding cfg file.
 			// all settings should be reset to default value.
@@ -112,7 +112,7 @@ namespace YYCC::ConfigManager {
 
 	bool CoreManager::Save() {
 		// get file handle
-		auto fs = this->GetFileHandle(YYCC_U8("wb"));
+		IOHelper::SmartStdFile fs(IOHelper::UTF8FOpen(m_CfgFilePath.c_str(), YYCC_U8("wb")));
 		// if we fail to get, return false.
 		if (fs == nullptr) return false;
 
@@ -157,15 +157,6 @@ namespace YYCC::ConfigManager {
 		}
 	}
 
-	CoreManager::FileHandleGuard_t CoreManager::GetFileHandle(const yycc_char8_t* mode) const {
-		return CoreManager::FileHandleGuard_t(
-			IOHelper::UTF8FOpen(this->m_CfgFilePath.c_str(), mode),
-			[](FILE* fs) -> void {
-				if (fs != nullptr) std::fclose(fs);
-			}
-		);
-	}
-
 #pragma endregion
 
 }
diff --git a/src/ConfigManager.hpp b/src/ConfigManager.hpp
index cb5d1c4..b5664a9 100644
--- a/src/ConfigManager.hpp
+++ b/src/ConfigManager.hpp
@@ -103,9 +103,6 @@ namespace YYCC::ConfigManager {
 		void Reset();
 
 	private:
-		using FileHandleGuard_t = std::unique_ptr<FILE, std::function<void(FILE*)>>;
-		FileHandleGuard_t GetFileHandle(const yycc_char8_t* mode) const;
-
 		yycc_u8string m_CfgFilePath;
 		uint64_t m_VersionIdentifier;
 		std::map<yycc_u8string, AbstractSetting*> m_Settings;
diff --git a/src/IOHelper.cpp b/src/IOHelper.cpp
index 5c91672..008645e 100644
--- a/src/IOHelper.cpp
+++ b/src/IOHelper.cpp
@@ -5,6 +5,7 @@
 #include <iostream>
 #include <string>
 #include <stdexcept>
+#include <memory>
 
 #if YYCC_OS == YYCC_OS_WINDOWS
 #include "WinImportPrefix.hpp"
@@ -13,8 +14,8 @@
 #endif
 
 namespace YYCC::IOHelper {
-
-	FILE* UTF8FOpen(const yycc_char8_t* u8_filepath, const yycc_char8_t* u8_mode) {
+	
+	std::FILE* UTF8FOpen(const yycc_char8_t* u8_filepath, const yycc_char8_t* u8_mode) {
 #if YYCC_OS == YYCC_OS_WINDOWS
 
 		// convert mode and file path to wchar
diff --git a/src/IOHelper.hpp b/src/IOHelper.hpp
index a6ef75e..34a78fd 100644
--- a/src/IOHelper.hpp
+++ b/src/IOHelper.hpp
@@ -27,6 +27,19 @@ namespace YYCC::IOHelper {
 #else
 #error "Not supported pointer size."
 #endif
+	
+	/// @brief C++ standard deleter for std::FILE*
+	class StdFileDeleter {
+	public:
+		StdFileDeleter() {}
+		void operator() (std::FILE* ptr) {
+			if (ptr != nullptr) {
+				std::fclose(ptr);
+			}
+		}
+	};
+	/// @brief Smart unique pointer of \c std::FILE*
+	using SmartStdFile = std::unique_ptr<std::FILE, StdFileDeleter>;
 
 	/**
 	 * @brief The UTF8 version of \c std::fopen.
@@ -37,6 +50,6 @@ namespace YYCC::IOHelper {
 	 * On other platforms, this function will delegate request directly to std::fopen.
 	 * @return \c FILE* of the file to be opened, or nullptr if failed.
 	*/
-	FILE* UTF8FOpen(const yycc_char8_t* u8_filepath, const yycc_char8_t* u8_mode);
+	std::FILE* UTF8FOpen(const yycc_char8_t* u8_filepath, const yycc_char8_t* u8_mode);
 	
 }
diff --git a/testbench/main.cpp b/testbench/main.cpp
index 878e914..c5439c9 100644
--- a/testbench/main.cpp
+++ b/testbench/main.cpp
@@ -457,8 +457,8 @@ namespace YYCCTestbench {
 		TestConfigManager test;
 
 		// test constraint works
-		Assert(!test.m_ClampedFloatSetting.Set(2.0f), YYCC_U8("YYCC::ConfigManager::Constraint"));
-		Assert(test.m_ClampedFloatSetting.Get() == 0.0f, YYCC_U8("YYCC::ConfigManager::Constraint"));
+		Assert(!test.m_ClampedFloatSetting.Set(2.0f), YYCC_U8("YYCC::Constraints::Constraint"));
+		Assert(test.m_ClampedFloatSetting.Get() == 0.0f, YYCC_U8("YYCC::Constraints::Constraint"));
 
 		// test modify settings
 #define TEST_MACRO(member_name, set_val) { \