[엔진 소스 코드 분석] 1 - LaunchWindows.cpp

1. 프로그램의 시작점 WinMain

int32 WINAPI WinMain(_In_ HINSTANCE hInInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ char* pCmdLine, _In_ int32 nCmdShow)
{
	// LaunchWidnowsStartup으로부터 엔진 루프까지
	int32 Result = LaunchWindowsStartup(hInInstance, hPrevInstance, pCmdLine, nCmdShow, nullptr);
	// 종료 전 해야할 일 처리
	LaunchWindowsShutdown();
    	// 실행 결과 반환
	return Result;
}

 

2. 엔진 시작점 LaunchWindowsStartup

LAUNCH_API int32 LaunchWindowsStartup( HINSTANCE hInInstance, HINSTANCE hPrevInstance, char*, int32 nCmdShow, const TCHAR* CmdLine )
{
	// 로깅을 위한 매크로 호출
	TRACE_BOOKMARK(TEXT("WinMain.Enter"));
    
    // 메모리 주소 취약점과 메모리 오류를 감지하기 위한 매크로가 선언된 경우의 처리
#if USING_ADDRESS_SANITISER
	__asan_set_error_report_callback(ASanErrorCallback);
#endif

	// Setup common Windows settings - 실행 인자 검증 및 Debug모드인 경우 메모리 누수 검출 활성화
	SetupWindowsEnvironment();

	int32 ErrorLevel			= 0;
	hInstance				= hInInstance;

	
	if (!CmdLine)
	{
		CmdLine = ::GetCommandLineW();

		// Attempt to process the command-line arguments using the standard Windows implementation
		// (This ensures behavior parity with other platforms where argc and argv are used.)
		if ( ProcessCommandLine() )
		{
			CmdLine = *GSavedCommandLine;
		}
	}

	// If we're running in unattended mode, make sure we never display error dialogs if we crash.
	if ( FParse::Param( CmdLine, TEXT("unattended") ) )
	{
		SetErrorMode(SEM_FAILCRITICALERRORS | SEM_NOGPFAULTERRORBOX | SEM_NOOPENFILEERRORBOX);
	}

	if ( FParse::Param( CmdLine,TEXT("crashreports") ) )
	{
		GAlwaysReportCrash = true;
	}

	uint32 LogicalCoreAffinity = 0;
	uint32 PhysicalCoreAffinity = 0;
	FParse::Value(CmdLine, TEXT("-processaffinity="), LogicalCoreAffinity);
	FParse::Value(CmdLine, TEXT("-processaffinityphysical="), PhysicalCoreAffinity);

	if (LogicalCoreAffinity > 0)
	{
		FWindowsPlatformProcess::SetProcessAffinity(LogicalCoreAffinity, false);
	}
	else if (PhysicalCoreAffinity > 0)
	{
		FWindowsPlatformProcess::SetProcessAffinity(PhysicalCoreAffinity, true);
	}

	bool bNoExceptionHandler = FParse::Param(CmdLine,TEXT("noexceptionhandler"));
	(void)bNoExceptionHandler;

	bool bIgnoreDebugger = FParse::Param(CmdLine, TEXT("IgnoreDebugger"));
	(void)bIgnoreDebugger;

	bool bIsDebuggerPresent = FPlatformMisc::IsDebuggerPresent() && !bIgnoreDebugger;
	(void)bIsDebuggerPresent;

	// Using the -noinnerexception parameter will disable the exception handler within native C++, which is call from managed code,
	// which is called from this function.
	// The default case is to have three wrapped exception handlers 
	// Native: WinMain() -> Native: GuardedMainWrapper().
	// The inner exception handler in GuardedMainWrapper() catches crashes/asserts in native C++ code and is the only way to get the
	// correct callstack when running a 64-bit executable. However, XAudio2 sometimes (?) don't like this and it may result in no sound.
#ifdef _WIN64
	if ( FParse::Param(CmdLine,TEXT("noinnerexception")) || FApp::IsBenchmarking() || bNoExceptionHandler)
	{
		GEnableInnerException = false;
	}
#endif	

	// When we're running embedded, assume that the outer application is going to be handling crash reporting
#if UE_BUILD_DEBUG
	if (GUELibraryOverrideSettings.bIsEmbedded || !GAlwaysReportCrash)
#else
	if (GUELibraryOverrideSettings.bIsEmbedded || bNoExceptionHandler || (bIsDebuggerPresent && !GAlwaysReportCrash))
#endif
	{
		// Don't use exception handling when a debugger is attached to exactly trap the crash. This does NOT check
		// whether we are the first instance or not!
		ErrorLevel = GuardedMain( CmdLine );
	}
	else
	{
		// Use structured exception handling to trap any crashes, walk the the stack and display a crash dialog box.
#if !PLATFORM_SEH_EXCEPTIONS_DISABLED
		__try
#endif
 		{
			GIsGuarded = 1;
			// Run the guarded code.
			ErrorLevel = GuardedMainWrapper( CmdLine );
			GIsGuarded = 0;
		}
#if !PLATFORM_SEH_EXCEPTIONS_DISABLED
		__except( FPlatformMisc::GetCrashHandlingType() == ECrashHandlingType::Default
				? ( GEnableInnerException ? EXCEPTION_EXECUTE_HANDLER : ReportCrash(GetExceptionInformation()) )
				: EXCEPTION_CONTINUE_SEARCH )	
		{
			// Crashed.
			ErrorLevel = 1;
			if(GError)
			{
				GError->HandleError();
			}
			LaunchStaticShutdownAfterError();
			FPlatformMallocCrash::Get().PrintPoolsUsage();
			FPlatformMisc::RequestExit( true, TEXT("LaunchWindowsStartup.ExceptionHandler"));
		}
#endif
	}

	TRACE_BOOKMARK(TEXT("WinMain.Exit"));

	return ErrorLevel;
}