Application crash even on a try catch block

Yanis 20

When i comment out the line GetViewsByZOrder i get the following exception:

Exception thrown at 0x00007FF96E36EE19 (rpcrt4.dll) in : 0xC0000005: Access violation reading location 0x00000000094F0122.

On the line if (collection->GetViewForHwnd(hwnd, &view) != S_OK)

#include <Windows.h>
#include <objectarray.h>
#include <atlbase.h>
#include <iostream>

struct __declspec(uuid("372E1D3B-38D3-42E4-A15B-8AB2B178F513")) IApplicationView : public IUnknown
{
};

struct __declspec(uuid("1841c6d7-4f9d-42c0-af41-8747538f10e5")) IApplicationViewCollection : public IUnknown
{
  public:
    virtual HRESULT STDMETHODCALLTYPE GetViews(IObjectArray **pArray) = 0;
    //virtual HRESULT STDMETHODCALLTYPE GetViewsByZOrder(IObjectArray **pArray) = 0;
    virtual HRESULT STDMETHODCALLTYPE GetViewsByAppUserModelId(BSTR pId, IObjectArray **pArray) = 0;
    virtual HRESULT STDMETHODCALLTYPE GetViewForHwnd(HWND pHwnd, IApplicationView **pView) = 0;
};

int main(int argc, char *argv[])
{
	static const CLSID CLSID_ImmersiveShell = { 0xC2F03A33, 0x21F5, 0x47FA, 0xB4, 0xBB, 0x15, 0x63, 0x62, 0xA2, 0xF2, 0x39 };

	CoInitialize(NULL);

    IServiceProvider* pServiceProvider = nullptr;
    if (CoCreateInstance(CLSID_ImmersiveShell, NULL, CLSCTX_LOCAL_SERVER, __uuidof(IServiceProvider), (PVOID*)&pServiceProvider) != S_OK)
        return 0;

    CComPtr<IApplicationViewCollection> collection = nullptr;
    if (pServiceProvider->QueryService(__uuidof(IApplicationViewCollection), &collection) != S_OK)
        return 0;

	CComPtr<IApplicationView> view;
    try
    {
        HWND hwnd  = FindWindowA(NULL, "Untitled - Notepad");
	    if (collection->GetViewForHwnd(hwnd, &view) != S_OK)  // <-- application crashes even being in the try block
		    return 0;
    }
    catch (...)
    {
        std::cout << "Exception" << std::endl;
    }
    return 0;
}

Without commenting the GetViewsByZOrder line it does work correctly.

I commented it just to ilustrate the issue, as these virtual functions can change between win builds.

I have also tried:

	CComPtr<IApplicationView> view;
    __try
    {
        HWND hwnd  = FindWindowA(NULL, "Untitled - Notepad");
	    if (collection->GetViewForHwnd(hwnd, &view) != S_OK)
		    return 0;
    }
    __except (EXCEPTION_EXECUTE_HANDLER)
    {
        std::cout << "Exception" << std::endl;
    }

But it doesnt compile, i get: error C2712: Cannot use __try in functions that require object unwinding

How i could safely read the GetViewForHwnd without getting an application crash?

Viorel 117.6K

Try something like this:

HRESULT TryGetViewForHwnd( const CComPtr<IApplicationViewCollection>& collection, HWND hwnd, CComPtr<IApplicationView>& view )
{
    __try
    {
        return collection->GetViewForHwnd( hwnd, &view );
    }
    __except( EXCEPTION_EXECUTE_HANDLER )
    {
        std::cout << "Exception" << std::endl;
        return E_FAIL;
    }
}

. . .

HWND hwnd = FindWindowA( NULL, "Untitled - Notepad" );
if( TryGetViewForHwnd( collection, hwnd, view ) != S_OK )
    return 0;

If Visual Studio shows the exception, press <F10> or <F5> to continue.

However, it is not safe to call unreliable code. Maybe there are methods to check the details of interface.

Minxin Yu 11,756 Reputation points Microsoft Vendor

2024-05-30T06:33:53.84+00:00

I did not find the document related to interface: IApplicationView, IApplicationViewCollection
May I know how you get the declarations?
Yanis 20 Reputation points

2024-05-30T14:50:40.1733333+00:00

These are undoc, i found searching around GitHub.
But my question is how to avoid the application to crash.
Yanis 20 Reputation points

2024-05-30T14:52:20.4733333+00:00

@Viorel i already tried this, its mentioned on my question:

error C2712: Cannot use __try in functions that require object unwinding
Viorel 117.6K Reputation points

2024-05-30T14:54:10.32+00:00

Maybe you should try again.

Accepted answer

RLWA32 45,576

Refer to Handle structured exceptions in C++ for information on catching an access violation or other exception.

Yanis 20 Reputation points

2024-05-30T14:49:40.42+00:00

Hello, i already tried __try/ __except, it doesn't compile.

RLWA32 45,576

You must set the /EHa compiler option -

SEHCatch

Now try running this outside the debugger (debugger may break on the first-chance exception) -

#include <stdio.h>
#include <tchar.h>

// Compile with /EHa

class CTest
{
public:
    CTest()
    {
        printf("In Constructor\n");
    }

    ~CTest()
    {
        printf("In Destructor\n");
    }
};


int main()
{
    try {
        CTest t;
        int* a = NULL;
        int b = *a;
    }
    catch (...)
    {
        printf("Caught access violation exception\n");
    }

    return 0;
}

You should see the output from the constructor, destructor and the exception handler.

Yanis 20

I enabled it, but it continue crashing, have you tried with the code on my question?

#include <Windows.h>
#include <objectarray.h>
#include <atlbase.h>
#include <iostream>

struct __declspec(uuid("372E1D3B-38D3-42E4-A15B-8AB2B178F513")) IApplicationView : public IUnknown
{
};

struct __declspec(uuid("1841c6d7-4f9d-42c0-af41-8747538f10e5")) IApplicationViewCollection : public IUnknown
{
  public:
    virtual HRESULT STDMETHODCALLTYPE GetViews(IObjectArray **pArray) = 0;
    //virtual HRESULT STDMETHODCALLTYPE GetViewsByZOrder(IObjectArray **pArray) = 0;
    virtual HRESULT STDMETHODCALLTYPE GetViewsByAppUserModelId(BSTR pId, IObjectArray **pArray) = 0;
    virtual HRESULT STDMETHODCALLTYPE GetViewForHwnd(HWND pHwnd, IApplicationView **pView) = 0;
};

int main(int argc, char *argv[])
{
    const CLSID CLSID_ImmersiveShell = { 0xC2F03A33, 0x21F5, 0x47FA, 0xB4, 0xBB, 0x15, 0x63, 0x62, 0xA2, 0xF2, 0x39 };

    CoInitialize(NULL);
    IServiceProvider* pServiceProvider = nullptr;
    if (CoCreateInstance(CLSID_ImmersiveShell, NULL, CLSCTX_LOCAL_SERVER, __uuidof(IServiceProvider), (PVOID*)&pServiceProvider) != S_OK)
        return 0;

    IApplicationViewCollection* collection = nullptr;
    if (pServiceProvider->QueryService(__uuidof(IApplicationViewCollection), &collection) != S_OK)
        return 0;

    IApplicationView* view = nullptr;
    __try
    {
        HWND hwnd = FindWindowA(NULL, "Untitled - Notepad");
        if (collection->GetViewForHwnd(hwnd, &view) != S_OK) // <-- crashes even being inside the __try block
            return 0;
    }
    __finally
    {
    }
    return 0;
}

RLWA32 45,576 Reputation points

2024-05-30T18:40:47.5133333+00:00

I enabled it, but it continue crashing, have you tried with the code on my question?

Yes, and as expected the access violation was caught in the exception handler!

And the printed message -

RLWA32 45,576

Another option is to restructure the code -

HRESULT DoMethod(IApplicationViewCollection* collection, IApplicationView** ppView)
{
    HRESULT hr;
    __try
    {
        HWND hwnd = FindWindowA(NULL, "Untitled - Notepad");
        hr = collection->GetViewForHwnd(hwnd, ppView);  // <-- application crashes even being in the try block
    }
    __except (GetExceptionCode() == EXCEPTION_ACCESS_VIOLATION ? EXCEPTION_EXECUTE_HANDLER : EXCEPTION_CONTINUE_SEARCH)
    {
        std::cout << "Exception" << std::endl;
        hr = E_FAIL;
    }

    return hr;
}

// Call the function 
    CComPtr<IApplicationViewCollection> collection = nullptr;
    if (pServiceProvider->QueryService(__uuidof(IApplicationViewCollection), &collection) != S_OK)
        return 0;

    CComPtr<IApplicationView> view;
    auto hr = DoMethod(collection, &view);

Yanis 20 Reputation points

2024-05-31T00:18:33.61+00:00

You are testing with GetViewsByZOrder commented?

You modified anything else other than the SEH exceptions option?

See:
RLWA32 45,576 Reputation points

2024-05-31T00:39:38.4966667+00:00

The debugger will always see an exception first. You can use visual studios exception settings to prevent the debugger from breaking on the exception. If you do this code execution should flow directly into the exception handler. Otherwise, you can just continue execution by pressing F5 or F10 after the debugger breaks.
Yanis 20 Reputation points

2024-05-31T03:43:26.1566667+00:00

I was so concerned about the exception message that i forget about this.

Thank you!
RLWA32 45,576 Reputation points

2024-05-31T07:59:51.2166667+00:00

You're welcome.

Restructuring the code so that only interface pointers are passed into the function containing the SEH exception handler eliminates the compiler error about functions requiring object unwinding.

The /EHa compiler option is needed if you want to use C++ exception handling to catch an SEH exception.

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Application crash even on a try catch block

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