How can I free the memory of a c++ safearray in c#

Question

I need to pass data from a C++ dll to a C# environment. Therefore I use a 2d SafeArray of doubles.

This function passes the data from C++ to C#:

void GetIndividualExposures(SAFEARRAY*& data)
{
    SAFEARRAYBOUND bounds[2];
    bounds[0].lLbound = 0;
    bounds[0].cElements = 10;
    bounds[1].lLbound = 0;
    bounds[1].cElements = 20;

    long l_dimensions[2];
    int index = 0;

    data = SafeArrayCreate(VT_R8, 2, bounds);
    double **pVals;

    HRESULT hr = SafeArrayAccessData(data, (void**)&pVals);
    if (SUCCEEDED(hr))
    {
        for (ULONG i = 0; i < bounds[0].cElements; i++)
        {
            for (ULONG j = 0; j < bounds[1].cElements; j++)
            {
                l_dimensions[0] = i;
                l_dimensions[1] = j;
                SafeArrayPutElement(data, l_dimensions, &data_source[i][j]);
            }
        }
        SafeArrayUnaccessData(data);
    }
}

This works, fine, all data is available as needed in my C# environment. However I get a memory leak. I tried to use a second C++ function to free the memory:

void DeallocateExternal(SAFEARRAY*& data)
{
    SafeArrayDestroy(data);
    data = NULL;
}

but it has no effect. What did I do wrong? Is there any possibility to free the memory of the SafeArray after use in C#? Or how can I do this?

I'm not sure. I think in the question you proposed, no SafeArray is used (or I do not understand it). I'm sorry. — JKlein, Aug 18 '17 at 12:52
Put HRESULT hr inside the "IF". When i(SUCCEEDED(hr)) is false you are not freeing the memory. — jdweng, Aug 18 '17 at 12:55
@Sinatr OP is talking about COM safe arrays not native buffers — , Aug 18 '17 at 13:02
A `SAFEARRAY` uses a shared heap. The caller can destroy it. You don't need to export a deallocator. — David Heffernan, Aug 18 '17 at 13:14
@David Heffernan Thank you, this helps a lot, but can you maybe Tell ne how to destroy it in C#? I'm quite nee to C#? Sorry! — JKlein, Aug 19 '17 at 18:12

How can I free the memory of a c++ safearray in c#

0 Answers0