破坏 _variant_t 导致断点 (C++)

Question

我遇到了麻烦terminating _variant_t types，触发断点导致程序崩溃，

引起问题的部分代码如下：

double ConnectToHYSYS::GetExergy() {

    //In this method, I'm using early Binding, so no more Dispatchs, lets get the interfaces themselves

    int i;
    HRESULT hr = hyStream->QueryInterface(IID_PPV_ARGS(&hyBackDoor));

    if (SUCCEEDED(hr)) {
        cout << "Got the BackDoor safely" << endl;

        // Get Array of CorrelationNames but in type _variant_t
        _variant_t t = _variant_t("HysysCorrelation.300.[]:Name.0");
        InternalVariableWrapper = hyBackDoor->GetBackDoorTextVariable(&t);
        TextFlexVariable = InternalVariableWrapper->GetVariable();
        _variant_t CorrelationNames= TextFlexVariable->GetValues();



        //Conversion of _variant_t type to safe Array

        SAFEARRAY *psa;
        psa = CorrelationNames.parray;


        // Loop through safeArray of BSTR
            BSTR* pVals;
        HRESULT hr = SafeArrayAccessData( psa, (void**)&pVals ); // direct access to SA memory
        if( SUCCEEDED( hr ) )
        {
            long lowerBound, upperBound;  // get array bounds
            SafeArrayGetLBound( psa, 1, &lowerBound );
            SafeArrayGetUBound( psa, 1, &upperBound );

            long cnt_elements = upperBound - lowerBound + 1;
            for( i = 0; i < cnt_elements; ++i )  // iterate through returned values
            {
                BSTR lVal = pVals[ i ];

                //Convert to normal String for comparison with Mass Exergy
                string CorrelationFinal= ConvertBSTRToMBS( lVal );
                std::cout << "element " << i << ": value = " << CorrelationFinal << std::endl;

                if( CorrelationFinal == "Mass Exergy" ){ break; }
            }
            SafeArrayUnaccessData( psa );
        }
        SafeArrayDestroy( psa );
        if (SUCCEEDED(hr)) {
            cout << "Got the BackDoor Text Variable safely" << endl;
        }

        if (FAILED(hr)) {
            cout << "Couldnt get the BackDoor Text Variable" << endl;
        }
    }

    if (FAILED(hr)) {
        cout << "Couldnt get the BackDoor" << endl;
    }
// Get Exergy Moniker
    string str = to_string(i);
    string ExergyMoniker ="HysysCorrelation.300." + str + ":ExtraData.550.0";

    // OLE accepts only _variant_t type and we need char array for that conversion... converting string to char array

    char tab2[ 1024 ];
    strncpy_s( tab2, ExergyMoniker.c_str(), sizeof( tab2 ) );
    tab2[ sizeof( tab2 ) - 1 ] = 0;

    //Get the exergy itself

    _variant_t t = _variant_t( tab2 );
    InternalVariableWrapper = hyBackDoor->GetBackDoorVariable( &t );
    RealVariable = InternalVariableWrapper->GetVariable();
    _variant_t ExergyValue = RealVariable->GetValue( "kJ/kg" );
    double ExergyValueDouble = ExergyValue.dblVal;

    return ExergyValueDouble;

那么，知道为什么会导致这样的错误吗？当我单击 "Break" 时，它指向此内联代码 (comutil.h)

inline _variant_t::~_variant_t() throw()
{
    ::VariantClear(this);
}

此外，当我在调试时单击继续时，程序继续正常运行，这是否意味着我可以处理该异常？

Answer 1

您的代码中存在许多潜在问题，例如，您所有的方法 GetBackDoorTextVariable()、GetValues()、GetBackDoorVariable()、GetValue() 都可能构建错误的变体。

但是，有一点似乎不太对劲，那就是您如何处理 CorrelationNames 实例。

因为 _variant_t 是一个自动包装器类并为您处理内存释放，所以您不应该对它玩得太深。但是在您的代码中，您释放了此变体持有的内存（使用 SafeArrayDestroy 调用），而不将 parray 成员设置为 null。当析构函数运行时，它会尝试释放空指针并崩溃。

因此，删除 SafeArrayDestroy(psa) 行，它应该会更好地工作，至少对于这个问题。

破坏 _variant_t 导致断点 (C++)

destructing _variant_t causes a break point (C++)

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