Codechange: refactor the Windows-only DllLoader in a cross-platform LibraryLoader

CMakeLists.txt

@@ -311,6 +311,7 @@ link_package(LZO)
 
 if(NOT WIN32 AND NOT EMSCRIPTEN)
     link_package(CURL ENCOURAGED)
+    target_link_libraries(openttd_lib ${CMAKE_DL_LIBS})
 endif()
 
 if(NOT EMSCRIPTEN)

src/CMakeLists.txt

@@ -232,6 +232,7 @@ add_files(
     league_gui.h
     league_gui.cpp
     league_type.h
+    library_loader.h
     livery.h
     main_gui.cpp
     map.cpp

src/library_loader.h

@@ -0,0 +1,112 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file library_loader.h Functions/types related to loading libraries dynamically. */
+
+#ifndef LIBRARY_LOADER_H
+#define LIBRARY_LOADER_H
+
+class LibraryLoader {
+public:
+	/**
+	 * A function loaded from a library.
+	 *
+	 * Will automatically cast to the correct function pointer type on retrieval.
+	 */
+	class Function {
+	public:
+		explicit Function(void *p) : p(p) {}
+
+		template <typename T, typename = std::enable_if_t<std::is_function_v<T>>>
+		operator T *() const
+		{
+			return reinterpret_cast<T *>(this->p);
+		}
+
+	private:
+		void *p;
+	};
+
+	/**
+	 * Load a library with the given filename.
+	 */
+	explicit LibraryLoader(const std::string &filename)
+	{
+		this->handle = this->OpenLibrary(filename);
+	}
+
+	/**
+	 * Close the library.
+	 */
+	~LibraryLoader()
+	{
+		if (this->handle != nullptr) {
+			this->CloseLibrary();
+		}
+	}
+
+	/**
+	 * Check whether an error occurred while loading the library or a function.
+	 *
+	 * @return Whether an error occurred.
+	 */
+	bool HasError()
+	{
+		return this->error.has_value();
+	}
+
+	/**
+	 * Get the last error that occurred while loading the library or a function.
+	 *
+	 * @return The error message.
+	 */
+	std::string GetLastError()
+	{
+		return this->error.value_or("No error");
+	}
+
+	/**
+	 * Get a function from a loaded library.
+	 *
+	 * @param symbol_name The name of the function to get.
+	 * @return The function. Check HasError() before using.
+	 */
+	Function GetFunction(const std::string &symbol_name)
+	{
+		if (this->error.has_value()) return Function(nullptr);
+		return Function(this->GetSymbol(symbol_name));
+	}
+
+private:
+	/**
+	 * Open the library with the given filename.
+	 *
+	 * Should set error if any error occurred.
+	 *
+	 * @param filename The filename of the library to open.
+	 */
+	void *OpenLibrary(const std::string &filename);
+
+	/**
+	 * Close the library.
+	 */
+	void CloseLibrary();
+
+	/**
+	 * Get a symbol from the library.
+	 *
+	 * Should set error if any error occurred.
+	 *
+	 * @param symbol_name The name of the symbol to get.
+	 */
+	void *GetSymbol(const std::string &symbol_name);
+
+	std::optional<std::string> error = {}; ///< The last error that occurred, if set.
+	void *handle = nullptr; ///< Handle to the library.
+};
+
+#endif /* LIBRARY_LOADER_H */

src/os/unix/CMakeLists.txt

@@ -5,6 +5,7 @@ add_files(
 )
 
 add_files(
+    library_loader_unix.cpp
     unix.cpp
     CONDITION UNIX
 )

src/os/unix/library_loader_unix.cpp

@@ -0,0 +1,64 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file library_loader_unix.cpp Implementation of the LibraryLoader for Linux / MacOS */
+
+#include "../../stdafx.h"
+
+#include <dlfcn.h>
+
+#include "../../library_loader.h"
+
+#include "../../safeguards.h"
+
+/* Emscripten cannot dynamically load other files. */
+#if defined(__EMSCRIPTEN__)
+
+void *LibraryLoader::OpenLibrary(const std::string &)
+{
+	this->error = "Dynamic loading is not supported on this platform.";
+	return nullptr;
+}
+
+void LibraryLoader::CloseLibrary()
+{
+}
+
+void *LibraryLoader::GetSymbol(const std::string &)
+{
+	this->error = "Dynamic loading is not supported on this platform.";
+	return nullptr;
+}
+
+#else
+
+void *LibraryLoader::OpenLibrary(const std::string &filename)
+{
+	void *h = dlopen(filename.c_str(), RTLD_NOW | RTLD_LOCAL);
+	if (h == nullptr) {
+		this->error = dlerror();
+	}
+
+	return h;
+}
+
+void LibraryLoader::CloseLibrary()
+{
+	dlclose(this->handle);
+}
+
+void *LibraryLoader::GetSymbol(const std::string &symbol_name)
+{
+	void *p = dlsym(this->handle, symbol_name.c_str());
+	if (p == nullptr) {
+		this->error = dlerror();
+	}
+
+	return p;
+}
+
+#endif /* __EMSCRIPTEN__ */

src/os/windows/CMakeLists.txt

@@ -2,6 +2,7 @@ add_files(
     crashlog_win.cpp
     font_win32.cpp
     font_win32.h
+    library_loader_win.cpp
     string_uniscribe.cpp
     string_uniscribe.h
     survey_win.cpp

src/os/windows/crashlog_win.cpp

@@ -17,6 +17,7 @@
 #include "../../gamelog.h"
 #include "../../saveload/saveload.h"
 #include "../../video/video_driver.hpp"
+#include "../../library_loader.h"
 
 #include <windows.h>
 #include <mmsystem.h>
@@ -177,7 +178,7 @@ static const uint MAX_FRAMES     = 64;
 
 /* virtual */ void CrashLogWindows::SurveyStacktrace(nlohmann::json &survey) const
 {
-	DllLoader dbghelp(L"dbghelp.dll");
+	LibraryLoader dbghelp("dbghelp.dll");
 	struct ProcPtrs {
 		BOOL (WINAPI * pSymInitialize)(HANDLE, PCSTR, BOOL);
 		BOOL (WINAPI * pSymSetOptions)(DWORD);
@@ -189,21 +190,21 @@ static const uint MAX_FRAMES     = 64;
 		BOOL (WINAPI * pSymGetSymFromAddr64)(HANDLE, DWORD64, PDWORD64, PIMAGEHLP_SYMBOL64);
 		BOOL (WINAPI * pSymGetLineFromAddr64)(HANDLE, DWORD64, PDWORD, PIMAGEHLP_LINE64);
 	} proc = {
-		dbghelp.GetProcAddress("SymInitialize"),
-		dbghelp.GetProcAddress("SymSetOptions"),
-		dbghelp.GetProcAddress("SymCleanup"),
-		dbghelp.GetProcAddress("StackWalk64"),
-		dbghelp.GetProcAddress("SymFunctionTableAccess64"),
-		dbghelp.GetProcAddress("SymGetModuleBase64"),
-		dbghelp.GetProcAddress("SymGetModuleInfo64"),
-		dbghelp.GetProcAddress("SymGetSymFromAddr64"),
-		dbghelp.GetProcAddress("SymGetLineFromAddr64"),
+		dbghelp.GetFunction("SymInitialize"),
+		dbghelp.GetFunction("SymSetOptions"),
+		dbghelp.GetFunction("SymCleanup"),
+		dbghelp.GetFunction("StackWalk64"),
+		dbghelp.GetFunction("SymFunctionTableAccess64"),
+		dbghelp.GetFunction("SymGetModuleBase64"),
+		dbghelp.GetFunction("SymGetModuleInfo64"),
+		dbghelp.GetFunction("SymGetSymFromAddr64"),
+		dbghelp.GetFunction("SymGetLineFromAddr64"),
 	};
 
 	survey = nlohmann::json::array();
 
 	/* Try to load the functions from the DLL, if that fails because of a too old dbghelp.dll, just skip it. */
-	if (dbghelp.Success()) {
+	if (!dbghelp.HasError()) {
 		/* Initialize symbol handler. */
 		HANDLE hCur = GetCurrentProcess();
 		proc.pSymInitialize(hCur, nullptr, TRUE);

src/os/windows/font_win32.cpp

@@ -15,9 +15,10 @@
 #include "../../core/mem_func.hpp"
 #include "../../error_func.h"
 #include "../../fileio_func.h"
-#include "../../fontdetection.h"
 #include "../../fontcache.h"
 #include "../../fontcache/truetypefontcache.h"
+#include "../../fontdetection.h"
+#include "../../library_loader.h"
 #include "../../string_func.h"
 #include "../../strings_func.h"
 #include "../../zoom_func.h"
@@ -361,9 +362,9 @@ void LoadWin32Font(FontSize fs)
 			if (AddFontResourceEx(fontPath, FR_PRIVATE, 0) != 0) {
 				/* Try a nice little undocumented function first for getting the internal font name.
 				 * Some documentation is found at: http://www.undocprint.org/winspool/getfontresourceinfo */
-				static DllLoader _gdi32(L"gdi32.dll");
+				static LibraryLoader _gdi32("gdi32.dll");
 				typedef BOOL(WINAPI *PFNGETFONTRESOURCEINFO)(LPCTSTR, LPDWORD, LPVOID, DWORD);
-				static PFNGETFONTRESOURCEINFO GetFontResourceInfo = _gdi32.GetProcAddress("GetFontResourceInfoW");
+				static PFNGETFONTRESOURCEINFO GetFontResourceInfo = _gdi32.GetFunction("GetFontResourceInfoW");
 
 				if (GetFontResourceInfo != nullptr) {
 					/* Try to query an array of LOGFONTs that describe the file. */

src/os/windows/font_win32.h

@@ -13,6 +13,8 @@
 #include "../../fontcache/truetypefontcache.h"
 #include "win32.h"
 
+#include <windows.h>
+
 /** Font cache for fonts that are based on a Win32 font. */
 class Win32FontCache : public TrueTypeFontCache {
 private:

src/os/windows/library_loader_win.cpp

@@ -0,0 +1,58 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file library_loader_win.cpp Implementation of the LibraryLoader for Windows */
+
+#include "../../stdafx.h"
+
+#include <windows.h>
+
+#include "../../library_loader.h"
+
+#include "../../safeguards.h"
+
+static std::string GetLoadError()
+{
+	auto error_code = GetLastError();
+
+	char buffer[512];
+	if (FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, nullptr, error_code,
+		MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), buffer, sizeof(buffer), nullptr) == 0) {
+		return fmt::format("Unknown error {}", error_code);
+	}
+
+	return buffer;
+}
+
+void *LibraryLoader::OpenLibrary(const std::string &filename)
+{
+	void *h = ::LoadLibraryW(OTTD2FS(filename).c_str());
+	if (h == nullptr) {
+		this->error = GetLoadError();
+	}
+
+	return h;
+}
+
+void LibraryLoader::CloseLibrary()
+{
+	HMODULE handle = static_cast<HMODULE>(this->handle);
+
+	::FreeLibrary(handle);
+}
+
+void *LibraryLoader::GetSymbol(const std::string &symbol_name)
+{
+	HMODULE handle = static_cast<HMODULE>(this->handle);
+
+	void *p = reinterpret_cast<void *>(::GetProcAddress(handle, symbol_name.c_str()));
+	if (p == nullptr) {
+		this->error = GetLoadError();
+	}
+
+	return p;
+}

src/os/windows/win32.cpp

@@ -27,6 +27,7 @@
 #include <sys/stat.h>
 #include "../../language.h"
 #include "../../thread.h"
+#include "../../library_loader.h"
 
 #include "../../safeguards.h"
 
@@ -573,8 +574,8 @@ int OTTDStringCompare(std::string_view s1, std::string_view s2)
 #endif
 
 	if (first_time) {
-		static DllLoader _kernel32(L"Kernel32.dll");
-		_CompareStringEx = _kernel32.GetProcAddress("CompareStringEx");
+		static LibraryLoader _kernel32("Kernel32.dll");
+		_CompareStringEx = _kernel32.GetFunction("CompareStringEx");
 		first_time = false;
 	}
 
@@ -617,8 +618,8 @@ int Win32StringContains(const std::string_view str, const std::string_view value
 	static bool first_time = true;
 
 	if (first_time) {
-		static DllLoader _kernel32(L"Kernel32.dll");
-		_FindNLSStringEx = _kernel32.GetProcAddress("FindNLSStringEx");
+		static LibraryLoader _kernel32("Kernel32.dll");
+		_FindNLSStringEx = _kernel32.GetFunction("FindNLSStringEx");
 		first_time = false;
 	}