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cwindowscomole

C IUknown_QueryInterface_Proxy cause General protection fault

I am trying to do some COM/OLE, here is my code :

static struct IUnknown* punk = NULL;
static IDispatch* UIRManager = NULL;

void DispatcherStart(){
    CoInitialize(NULL);
    HRESULT retour = GetActiveObject(&CLSID_OASIQ_,NULL,&punk);
     if(retour != S_OK){
        return;
    }
    HRESULT hr = IUnknown_QueryInterface_Proxy(punk,&IID_UIRManager_,(void**) &UIRManager); // General protection fault
...

For some reason, IUnknown_QueryInterface_Proxy cause a General protection fault. I dont see what I'm doing wrong ?

This function is called from a different thread than the main thread but since I call CoInitialize it's not the cause of error. I'm on C99 compiling a 32bit executable on W10

Solution

  • The C implementation of IUnknow is different than C++. The comon way to call QueryInterface is not by using IUnknown_QueryInterface_Proxy (from RpcRT4.lib) but to do this :

    HRESULT hr =  (punk)->lpVtbl -> QueryInterface(punk,&IID_UIRManager_,(void**) &UIRManager);