Possible undefined behaviour in fixpool.hh
While hunting a (in the end, unrelated) segmentation fault, I've tried enabling clang's UBsan and Asan on Spot. UBsan detects a possible undefined behavior in the fixed memory pool, on this line:
Adding a non zero offset to a nullptr seems to be undefined, more info here. I don't think this currently creates problems, but it seems like it could lead to UB in the future.
Note: UBsan on gcc 10.1.0 doesn't seem to detect this case, clang 10.0.0 does.