I got an illegal pointer

Hello, everyone!
I got an illegal pointer when using root to fit two-dimensional Gaussian distribution, as the following picture shows here. I don’t know what’s wrong, could you please help me? Thank you very much!
If you need the code of Gaus2D.c , please let me know.


the problem here is that TestGaus2D cannot be found and a null pointer is returned when looking for it.

Where is that object defined?

I see. Thanks a lot!
I thought the TestGaus2D was predefined, or preincluded somewhere in ROOT, but it seems not.
I found some introductory meterials through the internet, and I just followed the sentence in one of them. I still haven’t found another “TestGaus2D” in these documents except in the sentence I borrowed…