UnrealEngineUWP/Engine/Source/Programs/CrashReportClient/Private/Windows/CrashReportClientMainWindows.cpp

// Copyright Epic Games, Inc. All Rights Reserved.

#include "CrashReportClientApp.h"
#include "Windows/WindowsHWrapper.h"
#include "CrashReportClientDefines.h"

#if CRASH_REPORT_WITH_MTBF
#include "EditorAnalyticsSession.h"
#include "HAL/FileManager.h"
#include "HAL/PlatformProcess.h"
#include "HAL/PlatformAtomics.h"
#include "HAL/PlatformStackWalk.h"
#include "Serialization/Archive.h"
#include "DiagnosticLogger.h"
#endif

#if CRASH_REPORT_WITH_MTBF && !PLATFORM_SEH_EXCEPTIONS_DISABLED

static ANSICHAR CrashStackTrace[8*1024] = {0};

void SaveCrcCrashException(EXCEPTION_POINTERS* ExceptionInfo)
{
	// Try to write the exception code in the appropriate field if the session was created. The first crashing thread
	// incrementing the counter wins the race and can write its exception code.
	static volatile int32 CrashCount = 0;
	if (FPlatformAtomics::InterlockedIncrement(&CrashCount) == 1)
	{
		TCHAR CrashEventLog[64];
		FCString::Sprintf(CrashEventLog, TEXT("CRC/Crash:%d"), ExceptionInfo->ExceptionRecord->ExceptionCode);
		FDiagnosticLogger::Get().LogEvent(CrashEventLog);

		uint64 MonitoredEditorPid;
		if (FParse::Value(GetCommandLineW(), TEXT("-MONITOR="), MonitoredEditorPid))
		{
			FTimespan Timeout = FTimespan::FromSeconds(2);
			if (FEditorAnalyticsSession::Lock(Timeout)) // This lock is reentrant for the same process.
			{
				FEditorAnalyticsSession MonitoredSession;
				if (FEditorAnalyticsSession::FindSession(MonitoredEditorPid, MonitoredSession))
				{
					if (!MonitoredSession.SaveMonitorExceptCode(ExceptionInfo->ExceptionRecord->ExceptionCode))
					{
						FDiagnosticLogger::Get().LogEvent("CRC/ExceptCodeNotSaved");
					}
				}
				FEditorAnalyticsSession::Unlock();
			}
		}

		if (ExceptionInfo->ExceptionRecord->ExceptionCode != STATUS_HEAP_CORRUPTION)
		{
			// Try to get the exception callstack to log to figure out why CRC crashed. This is not robust because this runs
			// in the crashing processs and it allocates memory/use callstack, but we may still be able to get some useful data.
			if (FPlatformStackWalk::InitStackWalkingForProcess(FProcHandle()))
			{
				FPlatformStackWalk::StackWalkAndDump(CrashStackTrace, UE_ARRAY_COUNT(CrashStackTrace), 0);
				if (CrashStackTrace[0] != 0)
				{
					FDiagnosticLogger::Get().LogEvent(ANSI_TO_TCHAR(CrashStackTrace));
				}
			}
		}
	}
}

/**
 * The Vectored Exception Handler (VEH) is added to capture heap corruption exceptions because those are not reaching the
 * UnhandledExceptionFilter(). VEH has first and only chance to heap corrutpion exceptions before they got 'handled' by the OS.
 */
LONG WINAPI CrashReportVectoredExceptionFilter(EXCEPTION_POINTERS* ExceptionInfo)
{
	if (ExceptionInfo->ExceptionRecord->ExceptionCode == STATUS_HEAP_CORRUPTION)
	{
		SaveCrcCrashException(ExceptionInfo);
	}

	// Let the OS deal with the exception. (the process will crash)
	return EXCEPTION_CONTINUE_SEARCH;
}

/**
 * Invoked when an exception was not handled by vectored exception handler(s) nor structured exception handler(s)(__try/__except).
 * For good understanding a SEH inner working,take a look at EngineUnhandledExceptionFilter documentation in WindowsPlatformCrashContext.cpp.
 */
LONG WINAPI CrashReportUnhandledExceptionFilter(EXCEPTION_POINTERS* ExceptionInfo)
{
	SaveCrcCrashException(ExceptionInfo);

	// Let the OS deal with the exception. (the process will crash)
	return EXCEPTION_CONTINUE_SEARCH;
}
#endif

/**
 * WinMain, called when the application is started
 */
int WINAPI WinMain(_In_ HINSTANCE hInInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ LPSTR, _In_ int nCmdShow)
{
	hInstance = hInInstance;

#if CRASH_REPORT_WITH_MTBF // For the Editor only.
	FString Arguments(::GetCommandLineW());
	if (Arguments.Contains(TEXT("-MONITOR=")) && !Arguments.Contains(TEXT("-RespawnedInstance")))
	{
		uint64 ChildPipe = 0;
		FParse::Value(GetCommandLineW(), TEXT("-READ="), ChildPipe);

		// Parse the process ID of the Editor that spawned this CRC.
		uint32 MonitoredEditorPid = 0;
		if (FParse::Value(GetCommandLineW(), TEXT("-MONITOR="), MonitoredEditorPid))
		{
			TCHAR RespawnExePathname[MAX_PATH];
			GetModuleFileName(NULL, RespawnExePathname, MAX_PATH);
			FString RespawnExeArguments(Arguments);
			RespawnExeArguments.Append(" -RespawnedInstance");
			uint32 RespawnPid = 0;

			// Respawn itself to sever the process grouping with the Editor. If the user kills the Editor process group in task manager,
			// CRC will not die at the same time, will be able to capture the Editor exit code and send the MTBF report to correctly
			// identify the Editor 'AbnormalShutdown' as 'Killed' instead.
			FProcHandle Handle = FPlatformProcess::CreateProc(
				RespawnExePathname,
				*RespawnExeArguments,
				true, false, false,
				&RespawnPid, 0,
				nullptr,
				reinterpret_cast<void*>(ChildPipe), // Ensure the child process inherit this pipe handle that was previously inherited from its parent.
				nullptr);

			if (Handle.IsValid())
			{
				FString PidPathname = FString::Printf(TEXT("%sue4-crc-pid-%d"), FPlatformProcess::UserTempDir(), MonitoredEditorPid);
				if (TUniquePtr<FArchive> Ar = TUniquePtr<FArchive>(IFileManager::Get().CreateFileWriter(*PidPathname, FILEWRITE_EvenIfReadOnly)))
				{
					*Ar << RespawnPid;
				}
				
				FPlatformProcess::CloseProc(Handle);
			}
		}
		RequestEngineExit(TEXT("Respawn instance."));
		return 0; // Exit this intermediate instance, the Editor is waiting for it to continue.
	}

#if !PLATFORM_SEH_EXCEPTIONS_DISABLED
	::SetUnhandledExceptionFilter(CrashReportUnhandledExceptionFilter);
	::AddVectoredExceptionHandler(0, CrashReportVectoredExceptionFilter);
#endif // !PLATFORM_SEH_EXCEPTIONS_DISABLED
#endif // CRASH_REPORT_WITH_MTBF

	RunCrashReportClient(GetCommandLineW());
	return 0;
}