The OpenCL plugin tries to fetch a function pointer to the OpenCL core function clSetProgramSpecializationConstant.

However the OpenCL Extension specification does not guarantee, that core functions have to be returned by clSetProgramSpecializationConstant. 1.3. Getting OpenCL API Extension Function Pointers of the OpenCL Extension specification states:

"clGetExtensionFunctionAddressForPlatform may not be be used to query for core (non-extension) functions in OpenCL."

This function was added in OpenCL 2.2 and therefore calling and linking to it directly is the proper way. I'm not away of any extension which adds this or a similar function.