Return result with more error information when opening a shared library fails.

source/mijin/types/result.hpp

@@ -61,6 +61,14 @@ public:
 struct ResultError
 {
     std::string message;
+
+    ResultError() : message("Unknown error") {}
+    ResultError(const ResultError&) = default;
+    ResultError(ResultError&&) noexcept = default;
+    ResultError(std::string msg) noexcept : message(std::move(msg)) {}
+
+    ResultError& operator=(const ResultError&) = default;
+    ResultError& operator=(ResultError&&) noexcept = default;
 };
 
 template<typename TSuccess>

source/mijin/util/os.cpp

@@ -39,11 +39,18 @@ namespace mijin
 // public functions
 //
 
-LibraryHandle openSharedLibrary(std::string_view libraryFile) noexcept
+Result<LibraryHandle> openSharedLibrary(std::string_view libraryFile) noexcept
 {
 #if MIJIN_TARGET_OS == MIJIN_OS_LINUX
+    dlerror();
+
     const fs::path libraryPath = fs::absolute(libraryFile);
-    return {.data = dlopen(libraryPath.c_str(), RTLD_NOW)};
+    void* ptr = dlopen(libraryPath.c_str(), RTLD_NOW);
+    if (ptr == nullptr)
+    {
+        return ResultError(dlerror());
+    }
+    return LibraryHandle{.data = dlopen(libraryPath.c_str(), RTLD_NOW)};
 #elif MIJIN_TARGET_OS == MIJIN_OS_WINDOWS
 	// TODO
 	(void) libraryFile;

source/mijin/util/os.hpp

@@ -9,6 +9,7 @@
 #include <string_view>
 #include <utility>
 #include "../detect.hpp"
+#include "../types/result.hpp"
 
 namespace mijin
 {
@@ -62,7 +63,7 @@ public:
     constexpr operator bool() const noexcept { return static_cast<bool>(mHandle); }
     constexpr bool operator!() const noexcept { return !mHandle; }
 
-    [[nodiscard]] inline bool open(std::string_view libraryFile) noexcept;
+    [[nodiscard]] inline Result<bool> open(std::string_view libraryFile) noexcept;
     inline bool close() noexcept;
     [[nodiscard]] inline void* loadSymbol(const char* symbolName) noexcept;
 };
@@ -71,7 +72,7 @@ public:
 // public functions
 //
 
-[[nodiscard]] LibraryHandle openSharedLibrary(std::string_view libraryFile) noexcept;
+[[nodiscard]] Result<LibraryHandle> openSharedLibrary(std::string_view libraryFile) noexcept;
 bool closeSharedLibrary(const LibraryHandle library) noexcept;
 [[nodiscard]] void* loadSymbolFromLibrary(const LibraryHandle library, const char* symbolName) noexcept;
 void setCurrentThreadName(const char* threadName) noexcept;
@@ -83,11 +84,16 @@ SharedLibrary::~SharedLibrary() noexcept
     close();
 }
 
-bool SharedLibrary::open(std::string_view libraryFile) noexcept
+Result<bool> SharedLibrary::open(std::string_view libraryFile) noexcept
 {
     close();
-    mHandle = openSharedLibrary(libraryFile);
-    return static_cast<bool>(mHandle);
+    Result<LibraryHandle> openResult = openSharedLibrary(libraryFile);
+    if (openResult.isSuccess())
+    {
+        mHandle = openResult.getValue();
+        return true;
+    }
+    return ResultError(openResult.getError());
 }
 
 bool SharedLibrary::close() noexcept

source/mijin/util/property.hpp

@@ -80,7 +80,7 @@ public:
     Property(Property&&) noexcept = default;
 
     Property& operator=(Property&&) noexcept = default;
-    PropertyProxy operator*() const noexcept { return PropertyProxy(this); }
+    PropertyProxy operator*() noexcept { return PropertyProxy(this); }
     std::remove_reference_t<TGet>* operator->() const noexcept { return &get(); }
 
     [[nodiscard]] TGet get() const noexcept