Visual C++ Exception-Handling Instrumentation

Listing 3 Logging an exception

void PreviewException(void * pObject,
                      void * pThrowAddress, 
                      const type_info * pObjectInfo)
{
    pObject; //reference parameter
    if (pObjectInfo)
        std::cout << "Exception of type \"" 
                  << pObjectInfo->name() 
                  << "\" occured at " 
                  << pThrowAddress 
                  << "\n";
    
}


// this processor-specific function returns
// the return address of the caller
// assuming that callers frame was not optimized

__declspec(naked)
void * GetReturnAddress()
{
    __asm
    {
        mov eax, [ebp + 4]
        ret
    }
}

// this processor-specific function returns
// the stack frame of the caller's caller
// assuming that frames were not optimized

__declspec(naked)
void * GetCallerFrame()
{
    __asm
    {
        mov eax, [ebp]
        ret
    }
}

// imhibit optimization of frames
#pragma optimize("y",off)

extern "C"
void __stdcall _CxxThrowException(void * pObject,
                                  _s__ThrowInfo const * pObjectInfo)
{    
    void * paddr = GetReturnAddress();
    // call __CxxThrowException@8 is 5 bytes
    // long on i386. Subtracting 5 from return address
    // gives us the address of call instruction
paddr = (void*)((DWORD_PTR)paddr - 5);
    void * pframe = GetCallerFrame();

    type_info * pti = 0;
    // since we can get here when an exception is rethrown
    // pObjectInfo could be 0. Also it is a good idea to
    // make a sanity check
        if (pObjectInfo && 
            pObjectInfo->pCatchableTypeArray &&
            pObjectInfo->pCatchableTypeArray->nCatchableTypes > 0)
    {
        const _s__CatchableTypeArray * pTypes = 
            pObjectInfo->pCatchableTypeArray;
        pti = (type_info*) 
            ((*(pTypes->arrayOfCatchableTypes))[0].pType);
    }

    //call the hook function
    PreviewException(pObject,paddr,pti);

    const ULONG_PTR args[] = {MS_MAGIC,
                              (ULONG_PTR)pObject,
                              (ULONG_PTR)pObjectInfo};
    RaiseException(CPP_EXCEPTION,
                   EXCEPTION_NONCONTINUABLE,
                   sizeof(args)/sizeof(args[0]),
                   args);
}

//restore optimization settings
#pragma optimize("",on)