Summary:
CMerkleBlock::CMerkleBlock called IsRelevantAndUpdate() on each transaction
in order, which (due to the outpoint-adding feature) assumes a topological
order of transactions in order to work correctly. If an outpoint of
interest were created later in a block than when gets spent, then it would
be added into the bloom filter too late, and thus that spending transaction
would get missed.
This changes CMerkleBlock::CMerkleBlock to scan all outputs first, then
make a second loop to scan all inputs. This requires breaking up the
IsRelevantAndUpdate() function into two parts. The original
IsRelevantAndUpdate() functionality remains fully intact however, as it
gets called from mempool-related code (mempool has topological order) and
tests.
Note that vMatchedTxn.push_back is moved into the second loop so that index
i keeps ascending order, in case that is somehow relevant. (the tests at
least do check this)
A two-loop construction like this will very slightly increase the false
positive rate.
Originally by: Mark Lundeberg
tomFlowee
TomZ