Why does a bitmap compare not equal to itself?

Question

This is a bit puzzling here. The following code is part of a little testing application to verify that code changes didn\'t introduce a regression. To make it fast we used

Answer 1

Just an educated guess:

24 bits (3 bytes) is a little bit awkward on 32/64 bit hardware.

With this format there are bound to be buffers that are flushed out to a multiple of 4 bytes, leaving 1 or more bytes as 'don't care' . They can contain random data and the software doesn't feel obliged to zero them out. This will make memcmp fail.