First of all, I'm a beginner and I started to learn C++ last month, so don't be mad if I can't good explain the problem. :D
I'm using MS Detours to hook some custom functions to original functions from Windows. When I run the software, the original functions which are showing the text inside menus, windows etc. will be changed with my functions which are going to translate the text and show it like original function but just in the other language.
I have done the traditional hooking in C++ where I overwrite hot-patch header of function but the problem is that such hooking doesn't work with an 64-bit software and I realized that I can use MS Detours to do hooking because it is compatible with X86 and X64 software. The traditional hooking worked in 32 bit mode but after implementing MS Detours I get an error:
Unhandled exception at 0x6D3800C8 in Konfig32.exe: 0xC000041D: An unhandled exception was encountered during a user callback.
Here is a photo of it where you can see the function and the exception inside wincore.cpp file
The hooking worked and a checked with debugger that every function was successfully hooked to the original one.
Then the program starts to translate the text and it was successfull and after calling this function i got this error.
I searched for an answer in stackoverflow but none of them was connected with hooking, so it would be great if somebody can say what can be the possible problem or solution.
This is my source code:
// Constructor
CFunctionControll::CFunctionControll(BYTE* pOrigFunc, BYTE* pDetourFunc)
{
m_pOrigFunc = pOrigFunc;
m_pDetourFunc = pDetourFunc;
}
// Destructor
CFunctionControll::~CFunctionControll()
{
Disable();
}
void CFunctionControll::Enable()
{
try
{
DetourTransactionBegin();
DetourUpdateThread(GetCurrentThread());
DetourAttach(&(LPVOID&)m_pOrigFunc, m_pDetourFunc);
if (!DetourTransactionCommit())
throw transactionerror;
}
catch (TransactionError)
{
// Add proper exception handling later
}
}
void CFunctionControll::Disable()
{
try
{
DetourTransactionBegin();
DetourUpdateThread(GetCurrentThread());
DetourDetach(&(LPVOID&)m_pOrigFunc, m_pDetourFunc);
if (!DetourTransactionCommit())
throw transactionerror;
}
catch (TransactionError)
{
// Add proper exception handling later
}
}
class TransactionError : public std::exception
{
virtual const char* what() const throw()
{
return "DetourTransactionCommit() failed.";
}
} transactionerror;
The paramerer pOrigFunc is a pointer to the original function and the parameter pDetourFunc is a pointer to my customized function.
I am doing hooking with this CFunctionControll class where I can just say Enable()[to hook a function] or Disable()[to unhook it] :)
I have an ATL COM component which raises a few events which are handled by managed (C# and VB.NET) code. The component is currently used by a VS2005 VB.NET project (as an ActiveX control) and all of the events are raised and everything works.
However, in porting some of the code to C#, I noticed that all but one of the events are never raised. The only event which is raised passes no arguments back to the handler. All others do.
// this function is auto-generated
HRESULT Fire_SomeEvent(VARIANT_BOOL inOriginated, IUserType * inUserType)
{
CComVariant varResult;
T* pT = static_cast<T*>(this);
int nConnectionIndex;
CComVariant* pvars = new CComVariant[2];
int nConnections = m_vec.GetSize();
for (nConnectionIndex = 0; nConnectionIndex < nConnections; nConnectionIndex++)
{
pT->Lock();
CComPtr<IUnknown> sp = m_vec.GetAt(nConnectionIndex);
pT->Unlock();
IDispatch* pDispatch = reinterpret_cast<IDispatch*>(sp.p);
if (pDispatch != NULL)
{
VariantClear(&varResult);
pvars[1] = inOriginated;
pvars[0] = inUserType;
DISPPARAMS disp = { pvars, NULL, 2, 0 };
pDispatch->Invoke(0x7, IID_NULL, LOCALE_USER_DEFAULT, DISPATCH_METHOD, &disp, &varResult, NULL, NULL);
}
}
delete[] pvars;
return varResult.scode;
}
Invoke is returning 0x80070057 (E_INVALIDARG). Yet, in VB land, when used via the ActiveX wrapper, it works. Now, I'm no COM wizard by any means, and I just don't get it. I haven't been able to find anything applicable anywhere.
I thought that perhaps it had something to do with passing a UDT, but no; an almost identical version, with the IUserType replaced by a LONG also returns E_INVALIDARG. Again, the single event which passes no arguments works.
A short example of how it may be used by the managed code. Nothing crazy here.
class Program
{
private ComType _c;
static void Main(string[] args)
{
_c = new ComType();
_c.SomeEvent += _c_SomeEvent;
_c.DoSomethingWhichRaisesSomeEvent();
}
static void _c_SomeEvent(bool b, IUserType udt)
{
// never called
}
}
I would normally spend more time debugging before reaching out here, but I have to make a call here soon. I either have to fix this, or abandon this interface and use another (which is sub-optimal for my purpose). So, hoping some of you COM pros have run into this before.
Double-check your vt values in your dispparam variants; many IDispatch implementations are quite particular about having everything line up.
I have an ATL class. I'd like to know when QueryInterface of this class is called in order to remove memory leaks.
I added COM_INTERFACE_ENTRY_BREAK's in the COM_MAP, now it looks like:
BEGIN_COM_MAP( CMyClass )
COM_INTERFACE_ENTRY( IFace1 )
COM_INTERFACE_ENTRY( IFace2 )
//COM_INTERFACE_ENTRY_BREAK(IUnknown) // i included this too
COM_INTERFACE_ENTRY_BREAK( IFace1 )
COM_INTERFACE_ENTRY_BREAK( IFace2 )
END_COM_MAP()
When i start to debug (pressing F5) i have no breakpoint after the QI operation. I'm sure that QI is called because _ATL_DEBUG_INTERFACES shows a leak in the output window
ATL: QIThunk - 4 LEAK : Object = 0x02150CC0 Refcount = 1 MaxRefCount = 2 CMyClass - IUnknown
What should I do in order to have a breakpoint stopped at QI calling?
Thank you.
Clearly you want a breakpoint on the AddRef() call, not the QI call. Yes, painful, finding reference counting bugs in the client code from the server doesn't work very well if you use the ATL wrappers. Not otherwise fundamentally different from trying to diagnose memory leaks by setting a breakpoint on the new/delete operators, that doesn't work well either.
You can set a breakpoint on the InternalAddRef() method inside atlcom.h. But it can be noisy and it may cause the debugger to go catatonic for a while if you have a lot of interfaces in your server.
I've solved the problem with COM_INTERFACE_ENTRY_FUNC_BLIND macro like this:
BEGIN_COM_MAP(CMyClass)
COM_INTERFACE_ENTRY(IDummy) // NB!: this has to go before COM_INTERFACE_ENTRY_FUNC_BLIND
COM_INTERFACE_ENTRY_FUNC_BLIND(0, MyQueryInterface)
END_COM_MAP
MyQueryInterface is a function called every time an interface is querying.
My function is:
QueryInterfaceFunc ( void* pv, REFIID riid, LPVOID* ppv, DWORD dw )
{
if (riid == __uuidof(IFace1))
{
DebugBreak(); // Break here in the case of querying IFace1
}
}
I've written an ActiveX control in C++ that throws (C++) exceptions out when error conditions occur within the control. The Javascript code that invokes the object representing an instance of the control is surrounded by a try - catch block:
try
{
var controlInstance = window.controlInstance;
... perform operations on controlInstance ...
}
catch (e)
{
alert("something bad happened");
}
Now, when I run this code under IE8 (or 7 or 6) with a Visual Studio (2008) debugger attached to it, everything works as expected - whether the control is compiled with or without DEBUG on. However, when running the browser without a debugger attached, IE crashes (really) when an exception crosses the boundary between the control and JScript.
Does anyone have any suggestions around how to solve this problem? I realize that I can change the control's interface to pass the exception back as an argument but I really would rather not make such a change.
Any help would be appreciated.
How are you passing the exception from C++? A general throw does not work if you want to propagate your exception to javascript. You need to throw exception of type COleDispatchException and the right way to do is calling
AfxThrowOleDispatchException(101, _T("Exception Text Here")); // First parameter is exception code.
Reference: http://doc.sumy.ua/prog/active_x/ch03.htm#Heading20
You need AtlReportError. It throws javascript exception with description string:
STDMETHODIMP CMyCtrl::MyMethod()
{
...
if (bSucceeded)
return S_OK;
else
// hRes is set to DISP_E_EXCEPTION
return AtlReportError (GetObjectCLSID(), "My error message");
}
You can't pass C++ exceptions to the script - you need to catch the C++ exceptions in Invoke()/InvokeEx(), translate them and pass them out using the EXCEPINFO* parameter.
E.g. excerpting from FireBreath's implementation:
HRESULT YourIDispatchExImpl::InvokeEx(DISPID id, LCID lcid, WORD wFlags,
DISPPARAMS *pdp, VARIANT *pvarRes,
EXCEPINFO *pei, IServiceProvider *pspCaller)
{
try {
// do actual work
} catch (const cppException& e) {
if (pei != NULL) {
pei->bstrSource = CComBSTR(ACTIVEX_PROGID);
pei->bstrDescription = CComBSTR(e.what());
// ...
}
return DISP_E_EXCEPTION;
}
// ...
Is there any sense to step-execute release code? I noticed that some lines of code are omitted, i.e. some method calls. Also variable preview doesn't show some variables and shows invalid (not real) values for some others, so it's all quite misleading.
I'm asking this question, because loading WinDbg crashdump file into Visual Studio brings the same stack and variables partial view as step-execution. Are there any way to improve crashdump analyze experience, except recompiling application without optimalizations?
Windows, Visual Studio 2005, unmanaged C++
Yes - if you have the .pdb for the build, and the .dmp file from the crash, then you can open the debugger on the exact point of failure, and examine the state of your app at that point.
As several have noted - some variables will be optimized away, but if you're mildly creative / inquisitive, you'll find ways to obtain those values.
You can build in a root crash handler for your code to generate a .dmp file automatically which works on all Windows flavors (assuming you are creating a Windows app) using something like the following:
// capture the unhandled exception hook - we will create a mini dump for ourselves
// NOTE: according to docs, if a debugger is present, this API won't succeed (ie. debug builds ignore this)
MiniDumper::Install(
true,
filename,
"Please send a copy of this file, along with a brief description of the problem, to [insert your email address here] so that we might fix this issue."
);
The above would require the MiniDumper class I wrote, below:
#pragma once
#include <dbghelp.h>
#include "DynamicLinkLibrary.h"
#include "FileName.h"
//////////////////////////////////////////////////////////////////////////
// MiniDumper
//
// Provides a mechanism whereby an application will generate its own mini dump file anytime
// it throws an unhandled exception (or at the client's request - see GenerateMiniDump, below).
//
// Warning: the C-runtime will NOT invoke our unhandled handler if you are running a debugger
// due to the way that the SetUnhandledExceptionFilter() API works (q.v.)
//
// To use this facility, simply call MiniDumper::Install - for example, during CWinApp initialization.
//
// Once this has been installed, all current and future threads in this process will be covered.
// This is unlike the StructuredException and CRTInvalidParameter classes, which must be installed for
// for each thread for which you wish to use their services.
//
class MiniDumper
{
public:
// install the mini dumper (and optionally, hook the unhandled exception filter chain)
// #param filename is the mini dump filename to use (please include a path)
// #return success or failure
// NOTE: we can be called more than once to change our options (unhook unhandled, change the filename)
static bool Install(bool bHookUnhandledExceptionFilter, const CFilename & filenameMiniDump, const CString & strCustomizedMessage, DWORD dwMiniDumpType = MiniDumpNormal)
{
return GetSingleton().Initialize(bHookUnhandledExceptionFilter, filenameMiniDump, strCustomizedMessage, dwMiniDumpType);
}
// returns true if we've been initialized (but doesn't indicate if we have hooked the unhandled exception filter or not)
static bool IsInitialized() { return g_bInstalled; }
// returns true if we've been setup to intercept unhandled exceptions
static bool IsUnhandledExceptionHooked() { return g_bInstalled && GetSingleton().m_bHookedUnhandledExceptionFilter; }
// returns the filename we've been configured to write to if we're requested to generate a mini dump
static CFilename GetMiniDumpFilename() { return g_bInstalled ? GetSingleton().m_filenameMiniDump : ""; }
// you may use this wherever you have a valid EXCEPTION_POINTERS in order to generate a mini dump of whatever exception just occurred
// use the GetExceptionInformation() intrinsic to obtain the EXCEPTION_POINTERS in an __except(filter) context
// returns success or failure
// DO NOT hand the result of GenerateMiniDump to your __except(filter) - instead use a proper disposition value (q.v. __except)
// NOTE: you *must* have already installed MiniDumper or this will only error
static bool GenerateMiniDump(EXCEPTION_POINTERS * pExceptionPointers);
private:
// based on dbghelp.h
typedef BOOL (WINAPI * MINIDUMPWRITEDUMP_FUNC_PTR)(
HANDLE hProcess,
DWORD dwPid,
HANDLE hFile,
MINIDUMP_TYPE DumpType,
CONST PMINIDUMP_EXCEPTION_INFORMATION ExceptionParam,
CONST PMINIDUMP_USER_STREAM_INFORMATION UserStreamParam,
CONST PMINIDUMP_CALLBACK_INFORMATION CallbackParam
);
// data we need to pass to our mini dump thread
struct ExceptionThreadData
{
ExceptionThreadData(EXCEPTION_POINTERS * exceptionPointers, bool bUnhandled, DWORD threadID = ::GetCurrentThreadId())
: pExceptionPointers(exceptionPointers)
, dwThreadID(threadID)
, bUnhandledException(bUnhandled)
{
}
EXCEPTION_POINTERS * pExceptionPointers;
DWORD dwThreadID;
bool bUnhandledException;
};
// our unhandled exception filter (called automatically by the run time if we've been installed to do so)
static LONG CALLBACK UnhandledExceptionFilter(EXCEPTION_POINTERS * pExceptionPointers);
// creates a new thread in which to generate our mini dump (so we don't run out of stack)
static bool ExecuteMiniDumpThread(EXCEPTION_POINTERS * pExceptionPointers, bool bUnhandledException);
// thread entry point for generating a mini dump file
static DWORD WINAPI MiniDumpThreadProc(LPVOID lpParam);
// obtains the one and only instance
static MiniDumper & GetSingleton();
// flag to indicate if we're installed or not
static bool g_bInstalled;
// create us
MiniDumper()
: m_pPreviousFilter(NULL)
, m_pWriteMiniDumpFunction(NULL)
, m_bHookedUnhandledExceptionFilter(false)
{
}
// install our unhandled exception filter
bool Initialize(bool bHookUnhandledExceptionFilter, const CFilename & filenameMiniDump, const CString & strCustomizedMessage, DWORD dwMiniDumpType);
// generates a mini dump file
bool GenerateMiniDumpFile(ExceptionThreadData * pData);
// handle an unhandled exception
bool HandleUnhandledException(ExceptionThreadData * pData);
bool m_bHookedUnhandledExceptionFilter;
CFilename m_filenameMiniDump;
CString m_strCustomizedMessage;
DWORD m_dwMiniDumpType;
MINIDUMPWRITEDUMP_FUNC_PTR m_pWriteMiniDumpFunction;
LPTOP_LEVEL_EXCEPTION_FILTER m_pPreviousFilter;
};
And its implementation:
#include "StdAfx.h"
#include "MiniDumper.h"
using namespace Toolbox;
//////////////////////////////////////////////////////////////////////////
// Static Members
bool MiniDumper::g_bInstalled = false;
// returns true if we were able to create a mini dump for this exception
bool MiniDumper::GenerateMiniDump(EXCEPTION_POINTERS * pExceptionPointers)
{
// obtain the mini dump in a new thread context (which will have its own stack)
return ExecuteMiniDumpThread(pExceptionPointers, false);
}
// this is called from the run time if we were installed to hook the unhandled exception filter
LONG CALLBACK MiniDumper::UnhandledExceptionFilter(EXCEPTION_POINTERS * pExceptionPointers)
{
// attempt to generate the mini dump (use a separate thread to ensure this one is frozen & we have a fresh stack to work with)
ExecuteMiniDumpThread(pExceptionPointers, true);
// terminate this process, now
::TerminateProcess(GetCurrentProcess(), 0xFFFFFFFF);
// carry on as normal (we should never get here due to TerminateProcess, above)
return EXCEPTION_CONTINUE_SEARCH;
}
bool MiniDumper::ExecuteMiniDumpThread(EXCEPTION_POINTERS * pExceptionPointers, bool bUnhandledException)
{
// because this may have been created by a stack overflow
// we may be very very low on stack space
// so we'll create a new, temporary stack to work with until we fix this situation
ExceptionThreadData data(pExceptionPointers, bUnhandledException);
DWORD dwScratch;
HANDLE hMiniDumpThread = ::CreateThread(NULL, 0, MiniDumpThreadProc, &data, 0, &dwScratch);
if (hMiniDumpThread)
{
VERIFY(::WaitForSingleObject(hMiniDumpThread, INFINITE) == WAIT_OBJECT_0);
VERIFY(::GetExitCodeThread(hMiniDumpThread, &dwScratch));
VERIFY(::CloseHandle(hMiniDumpThread));
return AsBool(dwScratch);
}
return false;
}
DWORD WINAPI MiniDumper::MiniDumpThreadProc(LPVOID lpParam)
{
// retrieve our exception context from our creator
ExceptionThreadData * pData = (ExceptionThreadData *)lpParam;
// generate the actual mini dump file in this thread context - with our own stack
if (pData->bUnhandledException)
return GetSingleton().HandleUnhandledException(pData);
else
return GetSingleton().GenerateMiniDumpFile(pData);
}
bool MiniDumper::HandleUnhandledException(ExceptionThreadData * pData)
{
// generate the actual mini dump file first - hopefully we get this even if the following errors
const bool bMiniDumpSucceeded = GenerateMiniDumpFile(pData);
// try to inform the user of what's happened
CString strMessage = FString("An Unhandled Exception occurred in %s\n\nUnfortunately, this requires that the application be terminated.", CFilename::GetModuleFilename());
// create the mini dump file
if (bMiniDumpSucceeded)
{
// let user know about the mini dump
strMessage.AppendFormat("\n\nOn a higher note, we have saved some diagnostic information in %s", m_filenameMiniDump.c_str());
}
// append any custom message(s)
if (!IsEmpty(m_strCustomizedMessage))
strMessage.AppendFormat("\n\n%s", m_strCustomizedMessage);
// cap it off with an apology
strMessage.Append("\n\nThis application must be terminated now. All unsaved data will be lost. We are deeply sorry for the inconvenience.");
// let the user know that things have gone terribly wrong
::MessageBox(GetAppWindow(), strMessage, "Internal Error - Unhandled Exception", MB_ICONERROR);
// indicate success or not
return bMiniDumpSucceeded;
}
//////////////////////////////////////////////////////////////////////////
// Instance Members
MiniDumper & MiniDumper::GetSingleton()
{
static std::auto_ptr<MiniDumper> g_pSingleton(new MiniDumper);
return *g_pSingleton.get();
}
bool MiniDumper::Initialize(bool bHookUnhandledExceptionFilter, const CFilename & filenameMiniDump, const CString & strCustomizedMessage, DWORD dwMiniDumpType)
{
// check if we need to link to the the mini dump function
if (!m_pWriteMiniDumpFunction)
{
try
{
// attempt to load the debug helper DLL
DynamicLinkLibrary dll("DBGHelp.dll", true);
// get the function address we need
m_pWriteMiniDumpFunction = (MINIDUMPWRITEDUMP_FUNC_PTR)dll.GetProcAddress("MiniDumpWriteDump", false);
}
catch (CCustomException &)
{
// we failed to load the dll, or the function didn't exist
// either way, m_pWriteMiniDumpFunction will be NULL
ASSERT(m_pWriteMiniDumpFunction == NULL);
// there is nothing functional about the mini dumper if we have no mini dump function pointer
return false;
}
}
// record the filename to write our mini dumps to (NOTE: we don't do error checking on the filename provided!)
if (!IsEmpty(filenameMiniDump))
m_filenameMiniDump = filenameMiniDump;
// record the custom message to tell the user on an unhandled exception
m_strCustomizedMessage = strCustomizedMessage;
// check if they're updating the unhandled filter chain
if (bHookUnhandledExceptionFilter && !m_bHookedUnhandledExceptionFilter)
{
// we need to hook the unhandled exception filter chain
m_pPreviousFilter = ::SetUnhandledExceptionFilter(&MiniDumper::UnhandledExceptionFilter);
}
else if (!bHookUnhandledExceptionFilter && m_bHookedUnhandledExceptionFilter)
{
// we need to un-hook the unhandled exception filter chain
VERIFY(&MiniDumper::UnhandledExceptionFilter == ::SetUnhandledExceptionFilter(m_pPreviousFilter));
}
// set type of mini dump to generate
m_dwMiniDumpType = dwMiniDumpType;
// record that we've been installed
g_bInstalled = true;
// if we got here, we must have been successful
return true;
}
bool MiniDumper::GenerateMiniDumpFile(ExceptionThreadData * pData)
{
// NOTE: we don't check this before now because this allows us to generate an exception in a different thread context (rather than an exception while processing an exception in the main thread)
ASSERT(g_bInstalled);
if (!g_bInstalled)
return false;
HANDLE hFile = ::CreateFile(m_filenameMiniDump.c_str(), GENERIC_WRITE, FILE_SHARE_READ, NULL, CREATE_ALWAYS, FILE_ATTRIBUTE_NORMAL, NULL);
if (hFile == INVALID_HANDLE_VALUE)
{
// indicate failure
return false;
}
else
{
// NOTE: don't use exception_info - its a #define!!!
Initialized<_MINIDUMP_EXCEPTION_INFORMATION> ex_info;
ex_info.ThreadId = pData->dwThreadID;
ex_info.ExceptionPointers = pData->pExceptionPointers;
// generate our mini dump
bool bStatus = FALSE != ((*m_pWriteMiniDumpFunction)(GetCurrentProcess(), GetCurrentProcessId(), hFile, (MINIDUMP_TYPE)m_dwMiniDumpType, &ex_info, NULL, NULL));
// close the mini dump file
::CloseHandle(hFile);
return bStatus;
}
}
I apologize for the fact that this is not a drop-in solution. There are dependencies on other parts of my Toolbox library. But I think it would go a long way towards giving you the right idea as to how to build-in "capture a crash mini-dump" automatically from your code, which you can then combine with your .dsp files that you can make a normal part of your development cycle - so that when a .dmp comes in - you can fire up the debugger on it with your saved .pdb from your release build (which you don't distribute!) and you can debug the crash conditions quite easily.
The above code is an amalgam of many different sources - code snippets from debugging books, from MSDN documentation, etc., etc. If I have left out attribution I mean no harm. However, I do no believe that any of the above code is significantly created by anyone but myself.
Recompile just the file of interest without optimisations :)
In general:
Switch to interleaved disassembly mode. Single-stepping through the disassembly will enable you to step into function calls that would otherwise be skipped over, and make inlined code more evident.
Look for alternative ways of getting at values in variables the debugger is not able to directly show you. If they were passed in as arguments, look up the callstack - you will often find they are visible in the caller. If they were retrieved via getters from some object, examine that object; glance over the assembly generated by the code that calculates them to work out where they were stored; etc. If all else fails and disabling optimisations / adding a printf() distorts timings sufficiently to affect debugging, add a dummy global variable and set it to the value of interest on entry to the section of interest.
At least is not a IA64 dump...
There really isn't much you can do beyond having full dump and private symbols. Modern compilers have a field day with your code and is barely recognisable, specially if you add something like LTCG.
There are two things I found usefull:
Walk up the stack until you get a good anchor on what 'this' really points to. Most times when you are in an object method frame 'this' is unreliable because of registry optmizations. Usually several calls up the stack you get an object that has the correct address and you can navigate, member reference by member reference, until your crash point and have a correct value for 'this'
uf (Windbg's unassembly function command). This little helper can list a function dissasembly in a more manageable form than the normal dissasembly view. Because it follows jumps and code re-arranges, is easier to follow the logic of uf output.
The most important thing is to have the symbol files (*.pdb). You can generate them for release builds, by default they are not active.
Then you have to know that because of optimizations, code might get re-ordered, so debugging could look a bit jerky. Also some intermediate variables might have got optimized away. Generally speaking the behaviour and visibility of data might have some restrictions.
With Visual Studio C++ 2008 you can automatically debug the *.dmp files. I believe it also works for VS 2005. For older compilers I am afraid you´ll have to use WinDbg... (Also specify of course the *.pdb files for WinDbg, otherwise the info will be quite limited)