Make updater.exe a WIN32 GUI application instead of a console application on Windows

* Add WIN32 flag to add_executable() so that cmake generates a GUI application
 * Add WinMain() entry point which converts the unicode command line arguments to ANSI and then calls the standard main() entry point.

 The unit test continues to pass although I am not sure whether
 converting command-line args from Unicode to ANSI will cause problems
 with filenames passed on the command-line that contain non-ANSI
 characters.

src/CMakeLists.txt

@@ -82,9 +82,11 @@ if (UNIX)
   target_link_libraries(updatershared pthread)
 endif()
 
-add_executable(updater
-  main.cpp
-)
+if (WIN32)
+	set(EXE_FLAGS WIN32)
+endif()
+
+add_executable(updater ${EXE_FLAGS} main.cpp)
 
 if(APPLE)
 	set_target_properties(

src/ProcessUtils.cpp

@@ -401,4 +401,40 @@ std::string ProcessUtils::currentProcessPath()
 	return fileName;
 #endif
 }
+void ProcessUtils::convertWindowsCommandLine(LPCWSTR commandLine, int& argc, char**& argv)
+{
+	argc = 0;
+	LPWSTR* argvUnicode = CommandLineToArgvW(commandLine,&argc);
 
+	argv = new char*[argc];
+	for (int i=0; i < argc; i++)
+	{
+		const int BUFFER_SIZE = 4096;
+		char buffer[BUFFER_SIZE];
+
+		int length = WideCharToMultiByte(CP_ACP,
+		  0 /* flags */,
+		  argvUnicode[i],
+		  -1, /* argvUnicode is null terminated*/
+		  buffer,
+		  BUFFER_SIZE,
+		  0,
+		  false);
+
+		// note: if WideCharToMultiByte() fails it will return zero,
+		// in which case we store a zero-length argument in argv
+		if (length == 0)
+		{
+			argv[i] = new char[1];
+			argv[i][0] = '\0';
+		}
+		else
+		{
+			// if the input string to WideCharToMultiByte is null-terminated,
+			// the output is also null-terminated
+			argv[i] = new char[length];
+			strncpy(argv[i],buffer,length);
+		}
+	}
+	LocalFree(argvUnicode);
+}

src/ProcessUtils.h

@@ -23,6 +23,12 @@ class ProcessUtils
 
 		static bool waitForProcess(PLATFORM_PID pid);
 
+		/** Convert a unicode command line returned by GetCommandLineW()
+		 * to a standard (argc,argv) pair.  The resulting argv array and each
+		 * element of argv must be freed using free()
+		 */
+		static void convertWindowsCommandLine(LPCWSTR commandLine, int& argc, char**& argv);
+
 	private:
 		static void runElevatedLinux(const std::string& executable,
 		                             const std::list<std::string>& args);

src/main.cpp

@@ -1,5 +1,6 @@
 #include "Log.h"
 #include "Platform.h"
+#include "ProcessUtils.h"
 #include "StringUtils.h"
 #include "UpdateScript.h"
 #include "UpdaterOptions.h"
@@ -120,6 +121,18 @@ void runWithUi(int argc, char** argv, UpdateInstaller* installer)
 #endif
 
 #ifdef PLATFORM_WINDOWS
+// application entry point under Windows
+int CALLBACK WinMain(HINSTANCE hInstance,
+                     HINSTANCE hPrevInstance,
+                     LPSTR lpCmdLine,
+                     int nCmdShow)
+{
+	int argc = 0;
+	char** argv;
+	ProcessUtils::convertWindowsCommandLine(GetCommandLineW(),argc,argv);
+	return main(argc,argv);
+}
+
 void runWithUi(int argc, char** argv, UpdateInstaller* installer)
 {
 	UpdateDialogWin32 dialog;