Compatibility
Microsoft ended support for Windows XP on April 8th, 2014,
an OS initially released in 2001. This means that not even critical security
updates will be released anymore. Without security updates, using a bitcoin
wallet on a XP machine is irresponsible at least.
In addition to that, with 0.12.x there have been varied reports of Bitcoin Core
randomly crashing on Windows XP. It is not clear
what the source of these crashes is, but it is likely that upstream
libraries such as Qt are no longer being tested on XP.
We do not have time nor resources to provide support for an OS that is
end-of-life. From 0.13.0 on, Windows XP is no longer supported. Users are
suggested to upgrade to a newer verion of Windows, or install an alternative OS
that is supported.
No attempt is made to prevent installing or running the software on Windows XP,
you can still do so at your own risk, but do not expect it to work: do not
report issues about Windows XP to the issue tracker.
Notable changes
Database cache memory increased
As a result of growth of the UTXO set, performance with the prior default
database cache of 100 MiB has suffered.
For this reason the default was changed to 300 MiB in this release.
For nodes on low-memory systems, the database cache can be changed back to
100 MiB (or to another value) by either:
- Adding
dbcache=100 in bitcoin.conf
- Changing it in the GUI under
Options → Size of database cache
Note that the database cache setting has the most performance impact
during initial sync of a node, and when catching up after downtime.
bitcoin-cli: arguments privacy
The RPC command line client gained a new argument, -stdin
to read extra arguments from standard input, one per line until EOF/Ctrl-D.
For example:
$ src/bitcoin-cli -stdin walletpassphrase
mysecretcode
120
..... press Ctrl-D here to end input
$
It is recommended to use this for sensitive information such as wallet
passphrases, as command-line arguments can usually be read from the process
table by any user on the system.
C++11 and Python 3
Various code modernizations have been done. The Bitcoin Core code base has
started using C++11. This means that a C++11-capable compiler is now needed for
building. Effectively this means GCC 4.7 or higher, or Clang 3.3 or higher.
When cross-compiling for a target that doesn’t have C++11 libraries, configure with
./configure --enable-glibc-back-compat ... LDFLAGS=-static-libstdc++.
For running the functional tests in qa/rpc-tests, Python3.4 or higher is now
required.
Linux ARM builds
Due to popular request, Linux ARM builds have been added to the uploaded
executables.
The following extra files can be found in the download directory or torrent:
bitcoin-${VERSION}-arm-linux-gnueabihf.tar.gz: Linux binaries for the most
common 32-bit ARM architecture.bitcoin-${VERSION}-aarch64-linux-gnu.tar.gz: Linux binaries for the most
common 64-bit ARM architecture.
ARM builds are still experimental. If you have problems on a certain device or
Linux distribution combination please report them on the bug tracker, it may be
possible to resolve them.
Note that Android is not considered ARM Linux in this context. The executables
are not expected to work out of the box on Android.
Compact Block support (BIP 152)
Support for block relay using the Compact Blocks protocol has been implemented
in PR 8068.
The primary goal is reducing the bandwidth spikes at relay time, though in many
cases it also reduces propagation delay. It is automatically enabled between
compatible peers.
BIP 152
As a side-effect, ordinary non-mining nodes will download and upload blocks
faster if those blocks were produced by miners using similar transaction
filtering policies. This means that a miner who produces a block with many
transactions discouraged by your node will be relayed slower than one with
only transactions already in your memory pool. The overall effect of such
relay differences on the network may result in blocks which include widely-
discouraged transactions losing a stale block race, and therefore miners may
wish to configure their node to take common relay policies into consideration.
Hierarchical Deterministic Key Generation
Newly created wallets will use hierarchical deterministic key generation
according to BIP32 (keypath m/0’/0’/k’).
Existing wallets will still use traditional key generation.
Backups of HD wallets, regardless of when they have been created, can
therefore be used to re-generate all possible private keys, even the
ones which haven’t already been generated during the time of the backup.
Attention: Encrypting the wallet will create a new seed which requires
a new backup!
Wallet dumps (created using the dumpwallet RPC) will contain the deterministic
seed. This is expected to allow future versions to import the seed and all
associated funds, but this is not yet implemented.
HD key generation for new wallets can be disabled by -usehd=0. Keep in
mind that this flag only has affect on newly created wallets.
You can’t disable HD key generation once you have created a HD wallet.
There is no distinction between internal (change) and external keys.
HD wallets are incompatible with older versions of Bitcoin Core.
Pull request, BIP 32
Segregated Witness
The code preparations for Segregated Witness (“segwit”), as described in BIP
141, BIP
143, BIP
144, and BIP
145 are
finished and included in this release. However, BIP 141 does not yet specify
activation parameters on mainnet, and so this release does not support segwit
use on mainnet. Testnet use is supported, and after BIP 141 is updated with
proposed parameters, a future release of Bitcoin Core is expected that
implements those parameters for mainnet.
Furthermore, because segwit activation is not yet specified for mainnet,
version 0.13.0 will behave similarly as other pre-segwit releases even after a
future activation of BIP 141 on the network. Upgrading from 0.13.0 will be
required in order to utilize segwit-related features on mainnet (such as signal
BIP 141 activation, mine segwit blocks, fully validate segwit blocks, relay
segwit blocks to other segwit nodes, and use segwit transactions in the
wallet, etc).
Mining transaction selection (“Child Pays For Parent”)
The mining transaction selection algorithm has been replaced with an algorithm
that selects transactions based on their feerate inclusive of unconfirmed
ancestor transactions. This means that a low-fee transaction can become more
likely to be selected if a high-fee transaction that spends its outputs is
relayed.
With this change, the -blockminsize command line option has been removed.
The command line option -blockmaxsize remains an option to specify the
maximum number of serialized bytes in a generated block. In addition, the new
command line option -blockmaxweight has been added, which specifies the
maximum “block weight” of a generated block, as defined by [BIP 141 (Segregated
Witness)] (https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki).
In preparation for Segregated Witness, the mining algorithm has been modified
to optimize transaction selection for a given block weight, rather than a given
number of serialized bytes in a block. In this release, transaction selection
is unaffected by this distinction (as BIP 141 activation is not supported on
mainnet in this release, see above), but in future releases and after BIP 141
activation, these calculations would be expected to differ.
For optimal runtime performance, miners using this release should specify
-blockmaxweight on the command line, and not specify -blockmaxsize.
Additionally (or only) specifying -blockmaxsize, or relying on default
settings for both, may result in performance degradation, as the logic to
support -blockmaxsize performs additional computation to ensure that
constraint is met. (Note that for mainnet, in this release, the equivalent
parameter for -blockmaxweight would be four times the desired
-blockmaxsize. See [BIP 141]
(https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki) for additional
details.)
In the future, the -blockmaxsize option may be removed, as block creation is
no longer optimized for this metric. Feedback is requested on whether to
deprecate or keep this command line option in future releases.
Reindexing changes
In earlier versions, reindexing did validation while reading through the block
files on disk. These two have now been split up, so that all blocks are known
before validation starts. This was necessary to make certain optimizations that
are available during normal synchronizations also available during reindexing.
The two phases are distinct in the Bitcoin-Qt GUI. During the first one,
“Reindexing blocks on disk” is shown. During the second (slower) one,
“Processing blocks on disk” is shown.
It is possible to only redo validation now, without rebuilding the block index,
using the command line option -reindex-chainstate (in addition to
-reindex which does both). This new option is useful when the blocks on disk
are assumed to be fine, but the chainstate is still corrupted. It is also
useful for benchmarks.
Removal of internal miner
As CPU mining has been useless for a long time, the internal miner has been
removed in this release, and replaced with a simpler implementation for the
test framework.
The overall result of this is that setgenerate RPC call has been removed, as
well as the -gen and -genproclimit command-line options.
For testing, the generate call can still be used to mine a block, and a new
RPC call generatetoaddress has been added to mine to a specific address. This
works with wallet disabled.
New bytespersigop implementation
The former implementation of the bytespersigop filter accidentally broke bare
multisig (which is meant to be controlled by the permitbaremultisig option),
since the consensus protocol always counts these older transaction forms as 20
sigops for backwards compatibility. Simply fixing this bug by counting more
accurately would have reintroduced a vulnerability. It has therefore been
replaced with a new implementation that rather than filter such transactions,
instead treats them (for fee purposes only) as if they were in fact the size
of a transaction actually using all 20 sigops.
Low-level P2P changes
-
The optional new p2p message “feefilter” is implemented and the protocol
version is bumped to 70013. Upon receiving a feefilter message from a peer,
a node will not send invs for any transactions which do not meet the filter
feerate. BIP 133
-
The P2P alert system has been removed in PR #7692 and the alert P2P message
is no longer supported.
-
The transaction relay mechanism used to relay one quarter of all transactions
instantly, while queueing up the rest and sending them out in batch. As
this resulted in chains of dependent transactions being reordered, it
systematically hurt transaction relay. The relay code was redesigned in PRs
<a href=”https://github.com/bitcoin/bitcoin/pull/7840”>#7840</a> and #8082, and now always batches transactions announcements while also
sorting them according to dependency order. This significantly reduces orphan
transactions. To compensate for the removal of instant relay, the frequency of
batch sending was doubled for outgoing peers.
-
Since PR #7840 the BIP35 mempool command is also subject to batch processing.
Also the mempool message is no longer handled for non-whitelisted peers when
NODE_BLOOM is disabled through -peerbloomfilters=0.
-
The maximum size of orphan transactions that are kept in memory until their
ancestors arrive has been raised in PR #8179 from 5000 to 99999 bytes. They
are now also removed from memory when they are included in a block, conflict
with a block, and time out after 20 minutes.
-
We respond at most once to a getaddr request during the lifetime of a
connection since PR #7856.
-
Connections to peers who have recently been the first one to give us a valid
new block or transaction are protected from disconnections since PR #8084.
Low-level RPC changes
-
RPC calls have been added to output detailed statistics for individual mempool
entries, as well as to calculate the in-mempool ancestors or descendants of a
transaction: see getmempoolentry, getmempoolancestors, getmempooldescendants.
-
gettxoutsetinfo UTXO hash (hash_serialized) has changed. There was a divergence between
32-bit and 64-bit platforms, and the txids were missing in the hashed data. This has been
fixed, but this means that the output will be different than from previous versions.
-
Full UTF-8 support in the RPC API. Non-ASCII characters in, for example,
wallet labels have always been malformed because they weren’t taken into account
properly in JSON RPC processing. This is no longer the case. This also affects
the GUI debug console.
-
Asm script outputs replacements for OP_NOP2 and OP_NOP3
-
OP_NOP2 has been renamed to OP_CHECKLOCKTIMEVERIFY by BIP
65
-
OP_NOP3 has been renamed to OP_CHECKSEQUENCEVERIFY by BIP
112
-
The following outputs are affected by this change:
- RPC
getrawtransaction (in verbose mode)
- RPC
decoderawtransaction
- RPC
decodescript
- REST
/rest/tx/ (JSON format)
- REST
/rest/block/ (JSON format when including extended tx details)
bitcoin-tx -json
-
The sorting of the output of the getrawmempool output has changed.
-
New RPC commands: generatetoaddress, importprunedfunds, removeprunedfunds, signmessagewithprivkey,
getmempoolancestors, getmempooldescendants, getmempoolentry,
createwitnessaddress, addwitnessaddress.
-
Removed RPC commands: setgenerate, getgenerate.
-
New options were added to fundrawtransaction: includeWatching, changeAddress, changePosition and feeRate.
Low-level ZMQ changes
- Each ZMQ notification now contains an up-counting sequence number that allows
listeners to detect lost notifications.
The sequence number is always the last element in a multi-part ZMQ notification and
therefore backward compatible. Each message type has its own counter.
PR #7762.
