diff --git a/wfassoc-cdylib/cbinding/wfassoc++.h b/wfassoc-cdylib/cbinding/wfassoc++.h
index cbdc4ff..df91eeb 100644
--- a/wfassoc-cdylib/cbinding/wfassoc++.h
+++ b/wfassoc-cdylib/cbinding/wfassoc++.h
@@ -24,8 +24,16 @@
  */
 namespace wfassocpp {
 
-/** @brief Type representing a null-terminated UTF-8 C-style string */
-using CString = wfassoc::WFCString;
+/** @brief Type representing a pointer to a null-terminated UTF-8 C-style string */
+using StrPtr = wfassoc::WFStrPtr;
+/**
+ * @brief Type representing an error code returned by FFI functions
+ *
+ * WFERROR_OK is the only value representing absolute success.
+ * Any other value's meaning is decided by this library,
+ * currently WFERROR_ERR represents a generic failure.
+ */
+using Error = wfassoc::WFError;
 /**
  * @brief Type representing a handle/token for managed objects
  *
@@ -39,10 +47,12 @@ using Token = wfassoc::WFToken;
  * This type is equivalent to the Win32 HICON type.
  */
 using HICON = wfassoc::WFHICON;
+/** @brief Invalid token value used as a sentinel for no object */
+constexpr Token INVALID_TOKEN = wfassoc::WF_INVALID_TOKEN;
 /** @brief Invalid icon handle value */
-using INVALID_HICON = wfassoc::WF_INVALID_HICON;
+constexpr HICON INVALID_HICON = wfassoc::WF_INVALID_HICON;
 /** @brief Invalid index value used for error conditions */
-using INVALID_INDEX = wfassoc::WF_INVALID_INDEX;
+constexpr size_t INVALID_INDEX = wfassoc::WF_INVALID_INDEX;
 /**
  * @brief Registration scope for file associations
  *
@@ -60,30 +70,15 @@ using View = wfassoc::WFView;
  * @private
  * @brief Check the result of a C API call and throw on failure
  *
- * @param[in] result Boolean result from a C API call
- * @throws std::runtime_error if result is false, with the error message from WFGetLastError()
+ * @param[in] result Error code returned from a C API call
+ * @throws std::runtime_error if result is not WFERROR_OK, with the error message from WFGetLastError()
  */
-inline void _Check(bool result) {
-    if (!result) {
+inline void _Check(wfassoc::WFError result) {
+    if (result != wfassoc::WFERROR_OK) {
         throw std::runtime_error(wfassoc::WFGetLastError());
     }
 }
 
-/**
- * @private
- * @brief Get the invalid token value
- *
- * In theory, invalid token value should be a constant value.
- * However, due to the library used in Rust side, this value can only be fetched at runtime.
- * This function caches the value on first call for subsequent use.
- *
- * @return An invalid token value
- */
-inline Token _INVALID_TOKEN() {
-    static Token v = wfassoc::WFInvalidToken();
-    return v;
-}
-
 /**
  * @brief Schema object for defining a program's file association configuration
  *
@@ -106,7 +101,7 @@ public:
      * Releases resources associated with the Schema object.
      */
     ~Schema() {
-        if (_token != _INVALID_TOKEN()) {
+        if (_token != INVALID_TOKEN) {
             wfassoc::WFSchemaDestroy(_token);
         }
     }
@@ -117,15 +112,15 @@ public:
     Schema& operator=(const Schema&) = delete;
 
     /** @brief Move constructor */
-    Schema(Schema&& other) noexcept : _token(other._token) { other._token = _INVALID_TOKEN(); }
+    Schema(Schema&& other) noexcept : _token(other._token) { other._token = INVALID_TOKEN; }
     /** @brief Move assignment operator */
     Schema& operator=(Schema&& other) noexcept {
         if (this != &other) {
-            if (_token != _INVALID_TOKEN()) {
+            if (_token != INVALID_TOKEN) {
                 wfassoc::WFSchemaDestroy(_token);
             }
             _token = other._token;
-            other._token = _INVALID_TOKEN();
+            other._token = INVALID_TOKEN;
         }
         return *this;
     }
@@ -240,7 +235,7 @@ private:
      */
     Token Release() noexcept {
         Token t = _token;
-        _token = _INVALID_TOKEN();
+        _token = INVALID_TOKEN;
         return t;
     }
 
@@ -270,7 +265,7 @@ public:
      * Releases resources associated with the icon resource.
      */
     ~IconRc() {
-        if (_token != _INVALID_TOKEN()) {
+        if (_token != INVALID_TOKEN) {
             wfassoc::WFIconRcDestroy(_token);
         }
     }
@@ -281,15 +276,15 @@ public:
     IconRc& operator=(const IconRc&) = delete;
 
     /** @brief Move constructor */
-    IconRc(IconRc&& other) noexcept : _token(other._token) { other._token = _INVALID_TOKEN(); }
+    IconRc(IconRc&& other) noexcept : _token(other._token) { other._token = INVALID_TOKEN; }
     /** @brief Move assignment operator */
     IconRc& operator=(IconRc&& other) noexcept {
         if (this != &other) {
-            if (_token != _INVALID_TOKEN()) {
+            if (_token != INVALID_TOKEN) {
                 wfassoc::WFIconRcDestroy(_token);
             }
             _token = other._token;
-            other._token = _INVALID_TOKEN();
+            other._token = INVALID_TOKEN;
         }
         return *this;
     }
@@ -334,7 +329,7 @@ public:
      * Releases resources associated with the extension status.
      */
     ~ExtStatus() {
-        if (_token != _INVALID_TOKEN()) {
+        if (_token != INVALID_TOKEN) {
             wfassoc::WFExtStatusDestroy(_token);
         }
     }
@@ -345,15 +340,15 @@ public:
     ExtStatus& operator=(const ExtStatus&) = delete;
 
     /** @brief Move constructor */
-    ExtStatus(ExtStatus&& other) noexcept : _token(other._token) { other._token = _INVALID_TOKEN(); }
+    ExtStatus(ExtStatus&& other) noexcept : _token(other._token) { other._token = INVALID_TOKEN; }
     /** @brief Move assignment operator */
     ExtStatus& operator=(ExtStatus&& other) noexcept {
         if (this != &other) {
-            if (_token != _INVALID_TOKEN()) {
+            if (_token != INVALID_TOKEN) {
                 wfassoc::WFExtStatusDestroy(_token);
             }
             _token = other._token;
-            other._token = _INVALID_TOKEN();
+            other._token = INVALID_TOKEN;
         }
         return *this;
     }
@@ -415,7 +410,7 @@ public:
      * Releases resources associated with the self extension status.
      */
     ~SelfExtStatus() {
-        if (_token != _INVALID_TOKEN()) {
+        if (_token != INVALID_TOKEN) {
             wfassoc::WFSelfExtStatusDestroy(_token);
         }
     }
@@ -426,15 +421,15 @@ public:
     SelfExtStatus& operator=(const SelfExtStatus&) = delete;
 
     /** @brief Move constructor */
-    SelfExtStatus(SelfExtStatus&& other) noexcept : _token(other._token) { other._token = _INVALID_TOKEN(); }
+    SelfExtStatus(SelfExtStatus&& other) noexcept : _token(other._token) { other._token = INVALID_TOKEN; }
     /** @brief Move assignment operator */
     SelfExtStatus& operator=(SelfExtStatus&& other) noexcept {
         if (this != &other) {
-            if (_token != _INVALID_TOKEN()) {
+            if (_token != INVALID_TOKEN) {
                 wfassoc::WFSelfExtStatusDestroy(_token);
             }
             _token = other._token;
-            other._token = _INVALID_TOKEN();
+            other._token = INVALID_TOKEN;
         }
         return *this;
     }
@@ -525,7 +520,7 @@ public:
      * Releases resources associated with the Program.
      */
     ~Program() {
-        if (_token != _INVALID_TOKEN()) {
+        if (_token != INVALID_TOKEN) {
             wfassoc::WFProgramDestroy(_token);
         }
     }
@@ -536,15 +531,15 @@ public:
     Program& operator=(const Program&) = delete;
 
     /** @brief Move constructor */
-    Program(Program&& other) noexcept : _token(other._token) { other._token = _INVALID_TOKEN(); }
+    Program(Program&& other) noexcept : _token(other._token) { other._token = INVALID_TOKEN; }
     /** @brief Move assignment operator */
     Program& operator=(Program&& other) noexcept {
         if (this != &other) {
-            if (_token != _INVALID_TOKEN()) {
+            if (_token != INVALID_TOKEN) {
                 wfassoc::WFProgramDestroy(_token);
             }
             _token = other._token;
-            other._token = _INVALID_TOKEN();
+            other._token = INVALID_TOKEN;
         }
         return *this;
     }
@@ -576,7 +571,7 @@ public:
      * @throws std::runtime_error if the operation fails
      */
     IconRc ResolveIcon() {
-        Token token = _INVALID_TOKEN();
+        Token token = INVALID_TOKEN;
         _Check(wfassoc::WFProgramResolveIcon(_token, &token));
         return IconRc(token);
     }
@@ -614,7 +609,7 @@ public:
      * @throws std::runtime_error if the operation fails
      */
     SelfExtStatus ResolveExt(size_t index) {
-        Token token = _INVALID_TOKEN();
+        Token token = INVALID_TOKEN;
         _Check(wfassoc::WFProgramResolveExt(_token, index, &token));
         return SelfExtStatus(token);
     }
@@ -676,9 +671,9 @@ public:
      * @throws std::runtime_error if the operation fails
      */
     std::optional<ExtStatus> QueryExt(View view, size_t index) {
-        Token token = _INVALID_TOKEN();
+        Token token = INVALID_TOKEN;
         _Check(wfassoc::WFProgramQueryExt(_token, view, index, &token));
-        if (token == _INVALID_TOKEN()) {
+        if (token == INVALID_TOKEN) {
             return std::nullopt;
         }
         return ExtStatus(token);
diff --git a/wfassoc-cdylib/cbinding/wfassoc.h b/wfassoc-cdylib/cbinding/wfassoc.h
index 13f2ae4..246698c 100644
--- a/wfassoc-cdylib/cbinding/wfassoc.h
+++ b/wfassoc-cdylib/cbinding/wfassoc.h
@@ -34,7 +34,15 @@ namespace wfassoc {
 
 #ifdef __cplusplus
 /** Type representing a null-terminated UTF-8 C-style string */
-using WFCString = const char*;
+using WFStrPtr = const char*;
+/**
+ * @brief Type representing an error code returned by FFI functions
+ *
+ * WFERROR_OK is the only value representing absolute success.
+ * Any other value's meaning is decided by this library,
+ * currently WFERROR_ERR represents a generic failure.
+ */
+using WFError = uint32_t;
 /** 
  * @brief Type representing a handle/token for managed objects 
  * 
@@ -49,18 +57,28 @@ using WFToken = uint64_t;
  */
 using WFHICON = void*;
 #else  // __cplusplus
-typedef const char *WFCString;
+typedef const char *WFStrPtr;
+typedef uint32_t WFError;
 typedef uint64_t WFToken;
 typedef void *WFHICON;
 #endif  // __cplusplus
 
 
 #ifdef __cplusplus
+/** The error code representing absolute success. */
+constexpr WFError WFERROR_OK = 0u;
+/** The error code representing a generic failure. */
+constexpr WFError WFERROR_ERR = 1u;
+/** Invalid token value used as a sentinel for no object */
+constexpr WFToken WF_INVALID_TOKEN = 0u;
 /** Invalid icon handle value */
 constexpr WFHICON WF_INVALID_HICON = nullptr;
 /** Invalid index value used for error conditions */
 constexpr size_t WF_INVALID_INDEX = static_cast<size_t>(-1);
 #else  // __cplusplus
+static const WFError WFERROR_OK = 0u;
+static const WFError WFERROR_ERR = 1u;
+static const WFToken WF_INVALID_TOKEN = 0u;
 static const WFHICON WF_INVALID_HICON = NULL;
 static const size_t WF_INVALID_INDEX = ((size_t)-1);
 #endif  // __cplusplus
@@ -111,25 +129,6 @@ static const WFView WF_VIEW_HYBRID = 2u;
 extern "C" {
 #endif // __cplusplus
 
-/**
- * @brief Initialize the wfassoc library
- *
- * This function must be called before using the MOST of any other wfassoc functions.
- * 
- * @return true on success, false on failure.
- */
-bool WFStartup(void);
-
-/**
- * @brief Shutdown the wfassoc library
- *
- * Cleans up all allocated resources and object pools.
- * Should be called when done using the library.
- *
- * @return true on success, false on failure.
- */
-bool WFShutdown(void);
-
 /**
  * @brief Get the last error message
  *
@@ -137,46 +136,25 @@ bool WFShutdown(void);
  * The returned error message string is valid until the next API call.
  * 
  * For most functions located in this library, except some special function indicated in their notes,
- * they return boolean value indicating whether function is successful or not.
+ * they return WFERROR_OK when the function is successful, and WFERROR_ERR when the function is failed.
  * Once they fail, you can call this function to get a human-readable error message.
  * 
- * The execution of this function do not need to be wrapped by WFStartup() and WFShutdown().
- * 
  * The string this function return use different buffer with function return string value.
- * So you don't worry about that calling this function may invalidate function function return string value.
+ * So you don't worry about that calling this function may invalidate function return string value.
  *
  * @return Null-terminated UTF-8 string containing the error message.
  * If no error has occurred, the string is empty.
  * There is no possibility of a NULL return value.
  */
-WFCString WFGetLastError(void);
+WFStrPtr WFGetLastError(void);
 
 /**
  * @brief Check if the current process has administrative privileges
  *
- * This function will not throw any error.
- * There is no necessity to call WFGetLastError() after this function.
- * The return value only indicates whether the current process has administrative privileges or not.
- * 
- * The execution of this function do not need to be wrapped by WFStartup() and WFShutdown().
- *
- * @return true if running with admin privileges, false otherwise
+ * @param[out] out_has Pointer to receive whether the current process has administrative privileges.
+ * @return WFERROR_OK on success, WFERROR_ERR on failure.
  */
-bool WFHasPrivilege(void);
-
-/**
- * @brief Get an invalid token value
- *
- * In theory, invalid token value should be a constant value.
- * However, due to the library I used in Rust side, this value only can be fetched at runtime.
- * So I expose this function to make programmer can fetch this constant value.
- * Theoretically, you just need to fetch this function only once at the beginning of your program.
- * 
- * The execution of this function do not need to be wrapped by WFStartup() and WFShutdown().
- *
- * @return An invalid token value
- */
-WFToken WFInvalidWFToken(void);
+WFError WFHasPrivilege(bool *out_has);
 
 /**
  * @brief Create a new Schema object
@@ -189,9 +167,9 @@ WFToken WFInvalidWFToken(void);
  * The receiver take the ownership of this Schema object.
  * And it should be freed by calling WFSchemaDestroy() when it is no longer needed,
  * or consumed by creating a Program object via WFProgramCreate().
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSchemaCreate(WFToken *out_schema);
+WFError WFSchemaCreate(WFToken *out_schema);
 
 /**
  * @brief Destroy a Schema object
@@ -202,9 +180,9 @@ bool WFSchemaCreate(WFToken *out_schema);
  * because the convertion function from Schema to Program will consume given Schema object to produce Program object.
  *
  * @param[in] in_schema Schema token to destroy
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSchemaDestroy(WFToken in_schema);
+WFError WFSchemaDestroy(WFToken in_schema);
 
 /**
  * @brief Set the program identifier for a Schema
@@ -213,9 +191,9 @@ bool WFSchemaDestroy(WFToken in_schema);
  * @param[in] in_value Null-terminated UTF-8 string containing the identifier.
  * This identifier should not be empty, must start with alphabet character,
  * and follow with alphabet characters, digits, underline, or hyphens.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSchemaSetIdentifier(WFToken in_schema, WFCString in_value);
+WFError WFSchemaSetIdentifier(WFToken in_schema, WFStrPtr in_value);
 
 /**
  * @brief Set the program path for a Schema
@@ -223,9 +201,9 @@ bool WFSchemaSetIdentifier(WFToken in_schema, WFCString in_value);
  * @param[in] in_schema Schema token
  * @param[in] in_value Null-terminated UTF-8 string containing the program path.
  * This path should be the fully qualified path to the application.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSchemaSetPath(WFToken in_schema, WFCString in_value);
+WFError WFSchemaSetPath(WFToken in_schema, WFStrPtr in_value);
 
 /**
  * @brief Set the program CLSID for a Schema
@@ -234,36 +212,36 @@ bool WFSchemaSetPath(WFToken in_schema, WFCString in_value);
  * @param[in] in_value Null-terminated UTF-8 string containing the CLSID.
  * This CLSID string should be in the format of @c {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx} .
  * Please note that curly braces are required.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSchemaSetClsid(WFToken in_schema, WFCString in_value);
+WFError WFSchemaSetClsid(WFToken in_schema, WFStrPtr in_value);
 
 /**
  * @brief Set the program name for a Schema (optional)
  *
  * @param[in] in_schema Schema token
  * @param[in] in_value Null-terminated UTF-8 string containing the name, or NULL to clear
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSchemaSetName(WFToken in_schema, WFCString in_value);
+WFError WFSchemaSetName(WFToken in_schema, WFStrPtr in_value);
 
 /**
  * @brief Set the program icon for a Schema (optional)
  *
  * @param[in] in_schema Schema token
  * @param[in] in_value Null-terminated UTF-8 string containing the icon path, or NULL to clear
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSchemaSetIcon(WFToken in_schema, WFCString in_value);
+WFError WFSchemaSetIcon(WFToken in_schema, WFStrPtr in_value);
 
 /**
  * @brief Set the program behavior for a Schema (optional)
  *
  * @param[in] in_schema Schema token
  * @param[in] in_value Null-terminated UTF-8 string containing the behavior command, or NULL to clear
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSchemaSetBehavior(WFToken in_schema, WFCString in_value);
+WFError WFSchemaSetBehavior(WFToken in_schema, WFStrPtr in_value);
 
 /**
  * @brief Add a string resource entry to a Schema
@@ -272,9 +250,9 @@ bool WFSchemaSetBehavior(WFToken in_schema, WFCString in_value);
  * @param[in] in_name Null-terminated UTF-8 string containing the name of this entry
  * @param[in] in_value Null-terminated UTF-8 string containing the value of this entry.
  * It can be a plain string or a reference string to resource.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSchemaAddStr(WFToken in_schema, WFCString in_name, WFCString in_value);
+WFError WFSchemaAddStr(WFToken in_schema, WFStrPtr in_name, WFStrPtr in_value);
 
 /**
  * @brief Add an icon registry entry to a Schema
@@ -283,9 +261,9 @@ bool WFSchemaAddStr(WFToken in_schema, WFCString in_name, WFCString in_value);
  * @param[in] in_name Null-terminated UTF-8 string containing the name of this entry
  * @param[in] in_value Null-terminated UTF-8 string containing the value of this entry.
  * It can be a path to icon or a reference string to resource.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSchemaAddIcon(WFToken in_schema, WFCString in_name, WFCString in_value);
+WFError WFSchemaAddIcon(WFToken in_schema, WFStrPtr in_name, WFStrPtr in_value);
 
 /**
  * @brief Add a behavior registry entry to a Schema
@@ -294,9 +272,9 @@ bool WFSchemaAddIcon(WFToken in_schema, WFCString in_name, WFCString in_value);
  * @param[in] in_name Null-terminated UTF-8 string containing the name of this entry
  * @param[in] in_value Null-terminated UTF-8 string containing the value of this entry.
  * It should be a valid command line string which use \c %1, \c %2, etc. to represent parameters.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSchemaAddBehavior(WFToken in_schema, WFCString in_name, WFCString in_value);
+WFError WFSchemaAddBehavior(WFToken in_schema, WFStrPtr in_name, WFStrPtr in_value);
 
 /**
  * @brief Add a file extension to a Schema
@@ -309,13 +287,13 @@ bool WFSchemaAddBehavior(WFToken in_schema, WFCString in_name, WFCString in_valu
  * This name should be registered by calling WFSchemaAddIcon().
  * @param[in] in_ext_behavior Null-terminated UTF-8 string containing the name pointing to associated behavior for this extension.
  * This name should be registered by calling WFSchemaAddBehavior().
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSchemaAddExt(WFToken in_schema,
-                    WFCString in_ext,
-                    WFCString in_ext_name,
-                    WFCString in_ext_icon,
-                    WFCString in_ext_behavior);
+WFError WFSchemaAddExt(WFToken in_schema,
+                    WFStrPtr in_ext,
+                    WFStrPtr in_ext_name,
+                    WFStrPtr in_ext_icon,
+                    WFStrPtr in_ext_behavior);
 
 /**
  * @brief Create a Program object from a Schema
@@ -331,9 +309,9 @@ bool WFSchemaAddExt(WFToken in_schema,
  * @param[out] out_program Pointer to receive the Program token.
  * The receiver take the ownership of this Program object.
  * And it should be freed by calling WFProgramDestroy() when it is no longer needed.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFProgramCreate(WFToken in_schema, WFToken *out_program);
+WFError WFProgramCreate(WFToken in_schema, WFToken *out_program);
 
 /**
  * @brief Destroy a Program object
@@ -341,9 +319,9 @@ bool WFProgramCreate(WFToken in_schema, WFToken *out_program);
  * Releases resources associated with the Program.
  *
  * @param[in] in_program Program token to destroy
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFProgramDestroy(WFToken in_program);
+WFError WFProgramDestroy(WFToken in_program);
 
 /**
  * @brief Resolve the provided program name of this Program
@@ -356,9 +334,9 @@ bool WFProgramDestroy(WFToken in_program);
  * @param[out] out_name Pointer to receive the resolved name.
  * There is no possibility that this value is NULL.
  * This string will be freed at the next API call. Please make a copy immediately if you need to use it longer.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFProgramResolveName(WFToken in_program, WFCString *out_name);
+WFError WFProgramResolveName(WFToken in_program, WFStrPtr *out_name);
 
 /**
  * @brief Resolve the Program icon resource
@@ -371,18 +349,18 @@ bool WFProgramResolveName(WFToken in_program, WFCString *out_name);
  * @param[out] out_icon_rc Pointer to receive the icon resource token.
  * The caller take the ownership of created icon resource object.
  * And it should be freed by calling WFIconRcDestroy() when it is no longer needed.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFProgramResolveIcon(WFToken in_program, WFToken *out_icon_rc);
+WFError WFProgramResolveIcon(WFToken in_program, WFToken *out_icon_rc);
 
 /**
  * @brief Get the number of file extensions in the Program
  *
  * @param[in] in_program Program token
  * @param[out] out_len Pointer to receive the number of extensions
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFProgramExtsLen(WFToken in_program, size_t *out_len);
+WFError WFProgramExtsLen(WFToken in_program, size_t *out_len);
 
 /**
  * @brief Find a file extension by its body (extension string)
@@ -390,9 +368,9 @@ bool WFProgramExtsLen(WFToken in_program, size_t *out_len);
  * @param[in] in_program Program token
  * @param[in] in_body Null-terminated UTF-8 string containing the file extension name (without leading dot) to find.
  * @param[out] out_index Pointer to receive the file extension index, or WF_INVALID_INDEX if not found.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFProgramFindExt(WFToken in_program, WFCString in_body, size_t *out_index);
+WFError WFProgramFindExt(WFToken in_program, WFStrPtr in_body, size_t *out_index);
 
 /**
  * @brief Resolve this program provided extension's details by index
@@ -402,27 +380,27 @@ bool WFProgramFindExt(WFToken in_program, WFCString in_body, size_t *out_index);
  * @param[out] out_self_ext_status Pointer to receive the self extension status token.
  * The caller take the ownership of created self extension status object.
  * And it should be freed by calling WFSelfExtStatusDestroy() when it is no longer needed.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFProgramResolveExt(WFToken in_program, size_t in_index, WFToken *out_self_ext_status);
+WFError WFProgramResolveExt(WFToken in_program, size_t in_index, WFToken *out_self_ext_status);
 
 /**
  * @brief Register the Program in the specified scope
  *
  * @param[in] in_program Program token
  * @param[in] in_scope Registration scope
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFProgramRegister(WFToken in_program, WFScope in_scope);
+WFError WFProgramRegister(WFToken in_program, WFScope in_scope);
 
 /**
  * @brief Unregister the Program from the specified scope
  *
  * @param[in] in_program Program token
  * @param[in] in_scope Registration scope
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFProgramUnregister(WFToken in_program, WFScope in_scope);
+WFError WFProgramUnregister(WFToken in_program, WFScope in_scope);
 
 /**
  * @brief Check if the Program is registered in the specified scope
@@ -431,9 +409,9 @@ bool WFProgramUnregister(WFToken in_program, WFScope in_scope);
  * @param[in] in_scope Registration scope for checking
  * @param[out] out_is_registered Pointer to receive the registration status.
  * True if the Program is registered in the specified scope, false otherwise.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFProgramIsRegistered(WFToken in_program, WFScope in_scope, bool *out_is_registered);
+WFError WFProgramIsRegistered(WFToken in_program, WFScope in_scope, bool *out_is_registered);
 
 /**
  * @brief Link a file extension in the specified scope
@@ -441,9 +419,9 @@ bool WFProgramIsRegistered(WFToken in_program, WFScope in_scope, bool *out_is_re
  * @param[in] in_program Program token
  * @param[in] in_scope Registration scope
  * @param[in] in_index Index of the extension to link
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFProgramLinkExt(WFToken in_program, WFScope in_scope, size_t in_index);
+WFError WFProgramLinkExt(WFToken in_program, WFScope in_scope, size_t in_index);
 
 /**
  * @brief Unlink a file extension in the specified scope
@@ -451,9 +429,9 @@ bool WFProgramLinkExt(WFToken in_program, WFScope in_scope, size_t in_index);
  * @param[in] in_program Program token
  * @param[in] in_scope Registration scope
  * @param[in] in_index Index of the extension to unlink
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFProgramUnlinkExt(WFToken in_program, WFScope in_scope, size_t in_index);
+WFError WFProgramUnlinkExt(WFToken in_program, WFScope in_scope, size_t in_index);
 
 /**
  * @brief Query the status of a file extension
@@ -461,21 +439,21 @@ bool WFProgramUnlinkExt(WFToken in_program, WFScope in_scope, size_t in_index);
  * @param[in] in_program Program token
  * @param[in] in_view View viewpoint.
  * @param[in] in_index Index of the extension to query
- * @param[out] out_ext_status Pointer to receive the extension status token, or invalid token if not found.
+ * @param[out] out_ext_status Pointer to receive the extension status token, or WF_INVALID_TOKEN if not found.
  * If the extension is not found, it usually means that this extension is not registered in the specified scope.
  * The caller take the ownership of created extension status object.
  * And it should be freed by calling WFExtStatusDestroy() when it is no longer needed.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFProgramQueryExt(WFToken in_program, WFView in_view, size_t in_index, WFToken *out_ext_status);
+WFError WFProgramQueryExt(WFToken in_program, WFView in_view, size_t in_index, WFToken *out_ext_status);
 
 /**
  * @brief Destroy an extension status object
  *
  * @param[in] in_ext_status Extension status token to destroy
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFExtStatusDestroy(WFToken in_ext_status);
+WFError WFExtStatusDestroy(WFToken in_ext_status);
 
 /**
  * @brief Get the display name from an extension status object
@@ -488,9 +466,9 @@ bool WFExtStatusDestroy(WFToken in_ext_status);
  * There is no possibility that this value is NULL.
  * We will try to use localized name first, then use raw ProgId name if localized name is not available.
  * This string will be freed at the next API call. Please make a copy immediately if you need to use it longer.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFExtStatusGetName(WFToken in_ext_status, WFCString *out_name);
+WFError WFExtStatusGetName(WFToken in_ext_status, WFStrPtr *out_name);
 
 /**
  * @brief Get the icon from an extension status object
@@ -502,17 +480,17 @@ bool WFExtStatusGetName(WFToken in_ext_status, WFCString *out_name);
  * @param[out] out_icon Pointer to receive the icon handle.
  * This icon handle will be freed once this icon resource object is destroyed.
  * Please make a copy immediately if you need to use it longer.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFExtStatusGetIcon(WFToken in_ext_status, WFHICON *out_icon);
+WFError WFExtStatusGetIcon(WFToken in_ext_status, WFHICON *out_icon);
 
 /**
  * @brief Destroy a self extension status object
  *
  * @param[in] in_self_ext_status Self extension status token to destroy
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSelfExtStatusDestroy(WFToken in_self_ext_status);
+WFError WFSelfExtStatusDestroy(WFToken in_self_ext_status);
 
 /**
  * @brief Get the display name from a self extension status object
@@ -524,9 +502,9 @@ bool WFSelfExtStatusDestroy(WFToken in_self_ext_status);
  * @param[out] out_name Pointer to receive the name string.
  * There is no possibility that this value is NULL.
  * This string will be freed at the next API call. Please make a copy immediately if you need to use it longer.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSelfExtStatusGetName(WFToken in_self_ext_status, WFCString *out_name);
+WFError WFSelfExtStatusGetName(WFToken in_self_ext_status, WFStrPtr *out_name);
 
 /**
  * @brief Get the icon from a self extension status object
@@ -538,9 +516,9 @@ bool WFSelfExtStatusGetName(WFToken in_self_ext_status, WFCString *out_name);
  * @param[out] out_icon Pointer to receive the icon handle.
  * This icon handle will be freed once this self extension status object is destroyed.
  * Please make a copy immediately if you need to use it longer.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSelfExtStatusGetIcon(WFToken in_self_ext_status, WFHICON *out_icon);
+WFError WFSelfExtStatusGetIcon(WFToken in_self_ext_status, WFHICON *out_icon);
 
 /**
  * @brief Get the extension string (without leading dot) from a self extension status object
@@ -549,9 +527,9 @@ bool WFSelfExtStatusGetIcon(WFToken in_self_ext_status, WFHICON *out_icon);
  * @param[out] out_inner Pointer to receive the file extension name (without leading dot).
  * There is no possibility that this value is NULL.
  * This string will be freed at the next API call. Please make a copy immediately if you need to use it longer.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSelfExtStatusGetExt(WFToken in_self_ext_status, WFCString *out_inner);
+WFError WFSelfExtStatusGetExt(WFToken in_self_ext_status, WFStrPtr *out_inner);
 
 /**
  * @brief Get the dotted extension string (with leading dot) from a self extension status object
@@ -560,17 +538,17 @@ bool WFSelfExtStatusGetExt(WFToken in_self_ext_status, WFCString *out_inner);
  * @param[out] out_inner Pointer to receive the file extension string (with leading dot).
  * There is no possibility that this value is NULL.
  * This string will be freed at the next API call. Please make a copy immediately if you need to use it longer.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFSelfExtStatusGetDottedExt(WFToken in_self_ext_status, WFCString *out_inner);
+WFError WFSelfExtStatusGetDottedExt(WFToken in_self_ext_status, WFStrPtr *out_inner);
 
 /**
  * @brief Destroy an icon resource object
  *
  * @param[in] in_icon_rc Icon resource token to destroy
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFIconRcDestroy(WFToken in_icon_rc);
+WFError WFIconRcDestroy(WFToken in_icon_rc);
 
 /**
  * @brief Get the icon handle from an icon resource object
@@ -580,9 +558,9 @@ bool WFIconRcDestroy(WFToken in_icon_rc);
  * There is no possibility that this value is WF_INVALID_HICON.
  * This icon handle will be freed once this icon resource object is destroyed.
  * Please make a copy immediately if you need to use it longer.
- * @return true on success, false on failure
+ * @return WFERROR_OK on success, WFERROR_ERR on failure
  */
-bool WFIconRcGetIcon(WFToken in_icon_rc, WFHICON *out_icon);
+WFError WFIconRcGetIcon(WFToken in_icon_rc, WFHICON *out_icon);
 
 #ifdef __cplusplus
 }  // extern "C"