I have a 14bit lossy compressed NEF file from a Nikon D5500. I use the following code snippet to generate a raw histogram with libraw.

LibRaw processor;
processor.open_file(input_file);
processor.unpack()
// Create histogram from processor.imgdata.rawdata.raw_image

The generated histogram does not match the one I see in RawDigger.
The version of the libraw I am using does not have RAWSPEED support compiled in? Is this difference expected?