How to display the value of a pointer In MFC? - c++

Question

I have a capture card from Black Magic Design company. In related document it is described that the GetBytes method, from IDeckLinkVideoInputFrame interface, allows direct access to the data buffer of a video frame. Here is my work:
HRESULT DeckLinkDevice::VideoInputFrameArrived (/* in */ IDeckLinkVideoInputFrame* videoFrame, /* in */ IDeckLinkAudioInputPacket* audioPacket)
{
char* str1;
voidPtrToFrame = NULL;
videoFrame->GetBytes(&voidPtrToFrame);
sprintf(str1, "%p", voidPtrToFrame);
// the below line does not work.
SetDlgItemText(m_uiDelegate->GetSafeHwnd(), IDC_handytxtBox, str1);
}
I also defined voidPtrToFrame in class of DeckLinkDevice:
class DeckLinkDevice::IDeckLinkInputCallback
{
...
void* voidPtrToFrame;
...
}
In the last line an error appears related to str1:
argument of type "char*" is incompatible with parameter of type
LPCWSTR
I want to know:
How can I display the value of voidPtrToFrame in an Edit control? i.e. I want to present the address of buffer containing the video frame. In the following image I provided the necessary information about GetBytes method.
I googled a lot and tested several ways. But I could not implement them in MFC.

Answer 1

You have two problems:
1. You get a crash or at least undefined behaviour
The variable str1 is never initialized. It's a classic beginner's error.
The problem is here:
char* str1;
voidPtrToFrame = NULL;
videoFrame->GetBytes(&voidPtrToFrame);
// here str1 points to an interterminate location, it has never been
// initialized !! Therefore your program most likely will crash
sprintf(str1, "%p", voidPtrToFrame)
You need this:
char str1[20]; //<<< changement here
voidPtrToFrame = NULL;
videoFrame->GetBytes(&voidPtrToFrame);
// now str1 points to a 20 byte buffer
sprintf(str1, "%p", voidPtrToFrame);
2. You must use wide characters
You are compiling for unicode, therefore you need this (previous other corrections are included here):
wchar_t str1[20];
voidPtrToFrame = NULL;
videoFrame->GetBytes(&voidPtrToFrame);
wsprintf(str1, L"%p", voidPtrToFrame);
SetDlgItemText(m_uiDelegate->GetSafeHwnd(), IDC_handytxtBox, str1);