Access violation clGetPlatformIDs

Hello,
I am a student working to get some older OpenCL code running. It is an application that uses Matlab mex functions to call some C++. A Matlab script compiles the C++ code, then runs it to get the OpenCL stuff going.

The first OpenCL function called is

err = clGetPlatformIDs(0, 0, &nplatforms);

My understanding is that this should put the number of platforms in nplatforms, but I get an access violation instead and I’m not sure where to even start.

Thanks.