Every received block is assigned a unique and increasing identifier, so we know which one to give priority in case of a fork.
Declared in <validation.h>
int32_t nBlockSequenceId = SEQ_ID_INIT_FROM_DISK + 1;Blocks loaded from disk are assigned id SEQ_ID_INIT_FROM_DISK{1} (SEQ_ID_BEST_CHAIN_FROM_DISK{0} if they belong to the best chain loaded from disk), so start the counter after that. *