I'm very happy now, that after about two days of faffing around, I managed to get the compiler to generate a reasonably sized patch!
We need a way to generate binaries from C code, that can be patched with reasonably compact binary patches, since it's not really sensible to have an entire compiler (and bits) on board our instrument on the spacecraft !
I've worked out techniques and methods for generating binary files, where a minimum of the code moves around. Up until now, I had about 140000 bytes of change, in a 320000 byte binary, which whilst better, was really a bit ridiculous for a few dozen lines of change in the source code. Getting that
Total number of differences down to 1256 bytes is a major "Yay!" for me.