On 07/22/2015 05:13 PM, Eric Lombrozo via bitcoin-dev wrote:
> Only being partly serious - I strongly am in favor of a sufficiently
modularized codebase that swapping out consensus rules is fairly
straightforward and easy to test...

We (libbitcoin) have taken the time to publish and maintain bitcoind's
"libbitcoinconsensus" source files as an independent C++ library (with
Java and Python bindings).

https://en.bitcoin.it/wiki/Libbitcoin_Consensus

It can be easily verified against bitcoind sources and in builds of
libbitcoin-blockchain it can be swapped out for libbitcoin's native
consensus checks.

https://en.bitcoin.it/wiki/Libbitcoin_Blockchain#Consensus_Validation

So there is really no reason to consider the original client synonymous
with consensus. I initially argued for this library to be natively
isolated from bitcoind, but that didn't seem to be in the cards so we
did it independently.

In any case I agree with your stated need for this isolation (if not the
means) for the reasons you state. The community needs to move beyond a
largely singular and monolithic codebase that is holding that position
in part due to fear about consensus bug forks.

To make choice regarding consensus an actual choice (and thereby actual
consensus) the modularity you suggest is essential. One must be able to
take new developments without having to take consensus changes. The
option to fork the codebase is not reasonable for most people. At this
point there is no defensible reason for coupling consensus checks with
other features.

e