MinGW: Avoid function cast warnings with GetProcAddress

src/os/windows/crashlog_win.cpp

@@ -571,7 +571,7 @@ char *CrashLogWindows::AppendDecodedStacktrace(char *buffer, const char *last) c
 				CONST PMINIDUMP_EXCEPTION_INFORMATION,
 				CONST PMINIDUMP_USER_STREAM_INFORMATION,
 				CONST PMINIDUMP_CALLBACK_INFORMATION);
-		MiniDumpWriteDump_t funcMiniDumpWriteDump = (MiniDumpWriteDump_t)GetProcAddress(dbghelp, "MiniDumpWriteDump");
+		MiniDumpWriteDump_t funcMiniDumpWriteDump = GetProcAddressT<MiniDumpWriteDump_t>(dbghelp, "MiniDumpWriteDump");
 		if (funcMiniDumpWriteDump != nullptr) {
 			seprintf(filename, filename_last, "%scrash.dmp", _personal_dir.c_str());
 			HANDLE file  = CreateFile(OTTD2FS(filename).c_str(), GENERIC_WRITE, 0, nullptr, CREATE_ALWAYS, 0, 0);

src/os/windows/font_win32.cpp

@@ -623,7 +623,7 @@ void LoadWin32Font(FontSize fs)
 				/* Try a nice little undocumented function first for getting the internal font name.
 				 * Some documentation is found at: http://www.undocprint.org/winspool/getfontresourceinfo */
 				typedef BOOL(WINAPI *PFNGETFONTRESOURCEINFO)(LPCTSTR, LPDWORD, LPVOID, DWORD);
-				static PFNGETFONTRESOURCEINFO GetFontResourceInfo = (PFNGETFONTRESOURCEINFO)GetProcAddress(GetModuleHandle(L"Gdi32"), "GetFontResourceInfoW");
+				static PFNGETFONTRESOURCEINFO GetFontResourceInfo = GetProcAddressT<PFNGETFONTRESOURCEINFO>(GetModuleHandle(L"Gdi32"), "GetFontResourceInfoW");
 
 				if (GetFontResourceInfo != nullptr) {
 					/* Try to query an array of LOGFONTs that describe the file. */

src/os/windows/win32.cpp

@@ -40,10 +40,6 @@
 
 #include "../../safeguards.h"
 
-#ifdef __MINGW32__
-#pragma GCC diagnostic ignored "-Wcast-function-type"
-#endif /* __MINGW32__ */
-
 static bool _has_console;
 static bool _cursor_disable = true;
 static bool _cursor_visible = true;
@@ -71,13 +67,13 @@ bool LoadLibraryList(Function proc[], const char *dll)
 
 		if (lib == nullptr) return false;
 		for (;;) {
-			FARPROC p;
+			Function p;
 
 			while (*dll++ != '\0') { /* Nothing */ }
 			if (*dll == '\0') break;
-			p = GetProcAddress(lib, dll);
+			p = GetProcAddressT<Function>(lib, dll);
 			if (p == nullptr) return false;
-			*proc++ = (Function)p;
+			*proc++ = p;
 		}
 		dll++;
 	}
@@ -693,7 +689,7 @@ int OTTDStringCompare(const char *s1, const char *s2)
 #endif
 
 	if (first_time) {
-		_CompareStringEx = (PFNCOMPARESTRINGEX)GetProcAddress(GetModuleHandle(L"Kernel32"), "CompareStringEx");
+		_CompareStringEx = GetProcAddressT<PFNCOMPARESTRINGEX>(GetModuleHandle(L"Kernel32"), "CompareStringEx");
 		first_time = false;
 	}
 

src/os/windows/win32.h

@@ -26,4 +26,20 @@ wchar_t *convert_to_fs(const char *name, wchar_t *utf16_buf, size_t buflen);
 void Win32SetCurrentLocaleName(const char *iso_code);
 int OTTDStringCompare(const char *s1, const char *s2);
 
+#ifdef __MINGW32__
+			/* GCC doesn't understand the expected usage of GetProcAddress(). */
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wcast-function-type"
+#endif /* __MINGW32__ */
+
+template <typename T>
+T GetProcAddressT(HMODULE hModule, LPCSTR lpProcName)
+{
+	return reinterpret_cast<T>(GetProcAddress(hModule, lpProcName));
+}
+
+#ifdef __MINGW32__
+#pragma GCC diagnostic pop
+#endif
+
 #endif /* WIN32_H */

src/sound/xaudio2_s.cpp

@@ -158,7 +158,7 @@ const char *SoundDriver_XAudio2::Start(const StringList &parm)
 		return "Failed to load XAudio2 DLL";
 	}
 
-	API_XAudio2Create xAudio2Create = (API_XAudio2Create) GetProcAddress(_xaudio_dll_handle, "XAudio2Create");
+	API_XAudio2Create xAudio2Create = GetProcAddressT<API_XAudio2Create>(_xaudio_dll_handle, "XAudio2Create");
 
 	if (xAudio2Create == nullptr)
 	{

src/video/win32_v.cpp

@@ -962,9 +962,9 @@ float VideoDriver_Win32Base::GetDPIScale()
 	if (!init_done) {
 		init_done = true;
 
-		_GetDpiForWindow = (PFNGETDPIFORWINDOW)GetProcAddress(GetModuleHandle(L"User32"), "GetDpiForWindow");
-		_GetDpiForSystem = (PFNGETDPIFORSYSTEM)GetProcAddress(GetModuleHandle(L"User32"), "GetDpiForSystem");
-		_GetDpiForMonitor = (PFNGETDPIFORMONITOR)GetProcAddress(LoadLibrary(L"Shcore.dll"), "GetDpiForMonitor");
+		_GetDpiForWindow = GetProcAddressT<PFNGETDPIFORWINDOW>(GetModuleHandle(L"User32"), "GetDpiForWindow");
+		_GetDpiForSystem = GetProcAddressT<PFNGETDPIFORSYSTEM>(GetModuleHandle(L"User32"), "GetDpiForSystem");
+		_GetDpiForMonitor = GetProcAddressT<PFNGETDPIFORMONITOR>(LoadLibrary(L"Shcore.dll"), "GetDpiForMonitor");
 	}
 
 	UINT cur_dpi = 0;