Accept strings containing decimal values, in addition to bare values.
Useful from JSON-RPC implementations where it's not possible to have
direct control over the text of numbers (e.g. where numbers are always
doubles), and it's still desired to send an exact value.
This would allow users to post JSON content with numbers encoded like
`{"value": "0.00000001"}` instead of `{"value": 0.00000001}` which some
php/python encoders wrap into 1e-8, or worse.
060b3d3 fixup: qt 5.5 snuck in another module that needs path hand-holding (Cory Fields)
ecd6a89 depends: make more qt flags explicit (Cory Fields)
ab67dd7 depends: bump to qt 5.5 (Cory Fields)
5189fe3 depends: split qt config options to separate lines (Jacob Welsh)
fe997df build: fix building against qt5.4/5.5 (Cory Fields)
ec249d4 util: use locale-independent parsing in ParseDouble (Wladimir J. van der Laan)
7650449 univalue: Avoid unnecessary roundtrip through double for numbers (Wladimir J. van der Laan)
e061e27 rpc: Make ValueFromAmount always return 8 decimals (Wladimir J. van der Laan)
a794284 locking: add a quick example of GUARDED_BY (Cory Fields)
2b890dd locking: fix a few small issues uncovered by -Wthread-safety (Cory Fields)
cd27bba locking: teach Clang's -Wthread-safety to cope with our scoped lock macros (Cory Fields)
Handle the case where no chain tip is available, in InvalidChainFound(). This fixes a null pointer deference when running unit tests, if the genesis block or block validation code is broken.
This indicates that, eg, we have a public key for a key which may
be used as a pay-to-pubkey-hash. It generally means that we can
create a valid scriptSig except for missing private key(s) with
which to create signatures.
Since unspendable outputs can't be spent, there is no threshold at which it would be uneconomic to spend them.
This primarily targets transaction outputs with `OP_RETURN`.
---
Initially based on:
commit 9cf0ae26350033d43d5dd3c95054c0d1b1641eda
Author: zathras-crypto <zathrasc@gmail.com>
Date: Wed Mar 25 02:04:02 2015 -0700
Changes:
- cherry-picked on top of bitcoin:master
- added RPC test for fundrawtransaction
JSON makes no distinction between numbers and reals, and our code
doesn't need to do so either.
This removes VREAL, as well as its specific post-processing in
`UniValue::write`. Non-monetary amounts do not need to be forcibly
formatted with 8 decimals, so the extra roundtrip was unnecessary
(and potentially loses precision).
This is the format that was always returned to JSON clients.
The difference was not noticed before, because VREAL values
are post-processed by univalue.
By implementing the functionality directly it breaks the dependency
of rpcserver on utilmoneystr. FormatMoney is now only used for debugging
purposes.
To test, port over the formatting tests from util_tests.cpp to
rpc_tests.cpp.
QT_NO_KEYWORDS prevents Qt from defining the `foreach`, `signals`,
`slots` and `emit` macros.
Avoid overlap between Qt macros and boost - for example #undef hackiness
in #6421.
When no `-rpcpassword` is specified, use a special 'cookie' file for
authentication. This file is generated with random content when the
daemon starts, and deleted when it exits. Read access to this file
controls who can access through RPC. By default this file is stored in
the data directory but it be overriden with `-rpccookiefile`.
This is similar to Tor CookieAuthentication: see
https://www.torproject.org/docs/tor-manual.html.en
Alternative to #6258. Like that pull, this allows running bitcoind
without any manual configuration. However, daemons should ideally never write to
their configuration files, so I prefer this solution.
Add a function `ParseFixedPoint` that parses numbers according
to the JSON number specification and returns a 64-bit integer.
Then this in `AmountFromValue`, rather than `ParseMoney`.
Also add lots of tests (thanks to @jonasschnelli for some of them).
Fixes issue #6297.
I've never liked the chain-specific exception to having to set a
password. It gives issues with #6388 which makes it valid to
set no password in every case (as it enables random cookie authentication).
This pull removes the flag, so that all chains are regarded the same.
It also removes the username==password test, which doesn't provide any
substantial extra security.
Prevents stomping on debug logs in datadirs that are locked by other
instances and lost parameter interaction messages that can get wiped by
ShrinkDebugFile().
The log is now opened explicitly and all emitted messages are buffered
until this open occurs. The version message and log cut have also been
moved to the earliest possible sensible location.
Four cases included:
* The CLTV operand type mismatches the tx locktime. In the script it is
1 (interpreted as block height), but in the tx is 500000000
(interpreted as date)
* The stack is empty when executing OP_CLTV
* The tx is final by having only one input with MAX_INT sequence number
* The operand for CLTV is negative (after OP_0 OP_1 OP_SUB)
No longer relevant after #5957. This hack existed because of another
hack where the numthreads parameter, on regtest, doubled as how many
blocks to generate.
CTransAction::IsEquivalentTo was introduced in #5881.
This functionality is only useful to the wallet, and should never have
been added to the primitive transaction type.
72b9452 When processing RPC commands during warmup phase, parse the request object before returning an error so that id value can be used in the response. (Forrest Voight)
request object before returning an error so that id value can
be used in the response.
Prior to this commit, RPC commands sent during Bitcoin's
warmup/startup phase were responded to with a JSON-RPC error
with an id of null, which violated the JSON-RPC 2.0 spec:
id: This member is REQUIRED. It MUST be the same as the value
of the id member in the Request Object. If there was an error
in detecting the id in the Request object (e.g. Parse
error/Invalid Request), it MUST be Null.
To determine the default for `-par`, the number of script verification
threads, use [boost:🧵:physical_concurrency()](http://www.boost.org/doc/libs/1_58_0/doc/html/thread/thread_management.html#thread.thread_management.thread.physical_concurrency)
which counts only physical cores, not virtual cores.
Virtual cores are roughly a set of cached registers to avoid context
switches while threading, they cannot actually perform work, so spawning
a verification thread for them could even reduce efficiency and will put
undue load on the system.
Should fix issue #6358, as well as some other reported system overload
issues, especially on Intel processors.
The function was only introduced in boost 1.56, so provide a utility
function `GetNumCores` to fall back for older Boost versions.
4f40716 test: Move reindex test to standard tests (Wladimir J. van der Laan)
36c97b4 Bugfix: Don't check the genesis block header before accepting it (Jorge Timón)
ffd75ad Enable CHECKLOCKTIMEVERIFY as a standard script verify flag (Peter Todd)
bc60b2b Replace NOP2 with CHECKLOCKTIMEVERIFY (BIP65) (Peter Todd)
48e9c57 Move LOCKTIME_THRESHOLD to src/script/script.h (Peter Todd)
99088d6 Make CScriptNum() take nMaxNumSize as an argument (Peter Todd)
b932953 Hardcoded seeds update June 2015 (Wladimir J. van der Laan)
884454a contrib: Add port parsing to makeseeds.py (Wladimir J. van der Laan)
ccd4369 contrib: Improvements to hardcoded seeds scripts (Wladimir J. van der Laan)
New, undocumented-on-purpose -mocktime=timestamp command-line
argument to startup with mocktime set. Needed because
time-related blockchain sanity checks are done on startup, before a
test has a chance to make a setmocktime RPC call.
And changed the setmocktime RPC call so calling it will not result in
currently connected peers being disconnected due to inactivity timeouts.
Transactions that fail CLTV verification will be rejected from the
mempool, making it easy to test the feature. However blocks containing
"invalid" CLTV-using transactions will still be accepted; this is *not*
the soft-fork required to actually enable CLTV for production use.
<nLockTime> CHECKLOCKTIMEVERIFY -> <nLockTime>
Fails if tx.nLockTime < nLockTime, allowing the funds in a txout to be
locked until some block height or block time in the future is reached.
Only the logic and unittests are implemented; this commit does not have
any actual soft-fork logic in it.
Thanks to Pieter Wuille for rebase.
Credit goes to Gregory Maxwell for the suggestion of comparing the
argument against the transaction nLockTime rather than the current
time/blockheight directly.
When responding to a getblocks message, only return inv's as
long as we HAVE_DATA for blocks in the chain, and only for blocks
that we aren't likely to delete in the near future.
- fixes#3136
- the problem is related to Boost path and a static initialized internal
pointer
- using a std::string in CDBEnv::EnvShutdown() prevents the problem
- this removes the boost::filesystem::path path field from CDBEnv
26a639e remove using namespace std from addrman.cpp (Philip Kaufmann)
40c592a make CAddrMan::size() return the correct type of size_t (Philip Kaufmann)
For leveldb "An iterator operates on a snapshot of the database taken
when the iterator is created". This means that it is unnecessary to
lock out other threads while computing statistics, and neither to hold
cs_main for the whole time. Let the thread run free.
- rpcwallet: No need to lock twice here
- openssl: Clang doesn't understand selective lock/unlock here. Ignore it.
- CNode: Fix a legitimate (though very unlikely) locking bug.
This allows us to use function/variable/class attributes to specify locking
requisites, allowing problems to be detected during static analysis.
This works perfectly with newer Clang versions (tested with 3.3-3.7). For older
versions (tested 3.2), it compiles fine but spews lots of false-positives.
Make it possible to opt-out of the centralized alert system by providing
an option `-noalerts` or `-alerts=0`. The default remains unchanged.
This is a gentler form of #6260, in which I went a bit overboard by
removing the alert system completely.
I intend to add this to the GUI options in another pull after this.
This sets aside a number of connection slots for whitelisted peers,
useful for ensuring your local users and miners can always get in,
even if your limit on inbound connections has already been reached.
Chance "getbalance *" not to use IsTrusted. The method and result
now match the "getbalance <specific-account>" behavior. In
particular, "getbalance * 0" now works.
Also fixed a comment -- GetGalance has required 1 confirmation
for many years, and the default "getbalance *" behavior matches
that.
Simplify and make the code in AppInit2 more clear.
This provides a straightforward flow, gets rid of .count() (which makes
it possible to override an earlier provided proxy option to nothing), as
well as comments the different cases.
Univalue's parsing of \u escape sequences did not handle NUL characters
correctly. They were, effectively, dropped. The extended test-case
fails with the old code, and is fixed with this patch.
Do not translate -help-debug options, Many technical terms, and
only a very small audience, so is unnecessary stress to translators.
Brings the code up to date with translation string policy in
`doc/translation_strings_policy.md`.
Also remove no-longer-relevant "In this mode -genproclimit controls how
many blocks are generated immediately." (as of #5957) from regtest help.
7d8ffac Changes necessary now that zero values accepted in AmountFromValue (Wladimir J. van der Laan)
a04bdef Get rid of fPlus argument to FormatMoney (Wladimir J. van der Laan)
4b4b9a8 Don't go through double in AmountFromValue and ValueFromAmount (Wladimir J. van der Laan)
The partition checking code was using chainActive timestamps
to detect partitioning; with headers-first syncing, it should use
(and with this pull request, does use) pIndexBestHeader timestamps.
Fixes issue #6251
- Add an accept test for zero amounts, and a reject test for negative
amounts
- Remove ugly hack in `settxfee` that is no longer necessary
- Do explicit zero checks in wallet RPC functions
- Don't add a check for zero amounts in `createrawtransaction` - this
could be seen as a feature
My prime gripe with JSON spirit was that monetary values still had to be
converted from and to floating point which can cause deviations (see #3759
and https://bitcoin.stackexchange.com/questions/22716/bitcoind-sendfrom-round-amount-error).
As UniValue stores internal values as strings, this is no longer
necessary. This avoids risky double-to-integer and integer-to-double
conversions completely, and results in more elegant code to boot.
This prevents an edge case where a block downloaded and pruned
in-between successive calls to FindNextBlocksToDownload could
cause the block to be unnecessarily re-requested.
Strict parsing functions for other numeric types.
- ParseInt64 analogous to ParseInt32, but for 64-bit values.
- ParseDouble for doubles.
- Make all three Parse* functions more strict (e.g. reject whitespace on
the inside)
Also add tests.
- implement find_value() function for UniValue
- replace all Array/Value/Object types with UniValues, remove JSON Spirit to UniValue wrapper
- remove JSON Spirit sources
In some corner cases, it may be possible for recent blocks to end up in
the same block file as much older blocks. Previously, the pruning code
would stop looking for files to remove upon first encountering a file
containing a block that cannot be pruned, now it will keep looking for
candidate files until the target is met and all other criteria are
satisfied.
This can result in a noncontiguous set of block files (by number) on
disk, which is fine except for during some reindex corner cases, so
make reindex preparation smarter such that we keep the data we can
actually use and throw away the rest. This allows pruning to work
correctly while downloading any blocks needed during the reindex.
Change `read_string` to fail when not the entire input has been
consumed. This avoids unexpected, even dangerous behavior (fixes#6223).
The new JSON parser adapted in #6121 also solves this problem so in
master this is a temporary fix, but should be backported to older releases.
Also adds tests for the new behavior.
If/when CTransaction::CURRENT_VERSION is incremented, this will break CChainParams and the miner tests. This fix sets the transaction version explicitly where we depend on the hash value (genesis block, proof of work checks).
aa41bc8 Update help message to match the #4219 change (lpescher)
f60bb5e Update documentation to match the #4219 change (lpescher)
cb87386 Make command line option to show all debugging consistent with similar options (lpescher)
Under some circumstances it is possible for there to be a significant,
discontinuous jump in a node's clock value. On mining nodes, this can
result in block templates which are no longer valid due to time-based
nLockTime constraints. UpdateTime() is modified so that it will never
decrease a block's nLockTime, thereby preventing such invalidations.
Previously due to an off-by-one error the wallet ignored
nLockTime-by-height transactions that would be valid in the next block
even though they are accepted into the mempool. The transactions
wouldn't show up until confirmed, nor would they be included in the
unconfirmed balance. Similar to the mempool behavior fix in 665bdd3b,
the wallet code was calling IsFinalTx() directly without taking into
account the fact that doing so tells you if the transaction could have
been mined in the *current* block, rather than the next block.
To fix this we strip IsFinalTx() of non-consensus-critical
functionality, removing the default arguments, and add CheckFinalTx() to
check if a transaction will be final in the next block.
Fix two CSubNet constructor problems:
- The use of `/x` where 8 does not divide x was broken, due to a
bit-order issue
- The use of e.g. `1.2.3.4/24` where the netmasked bits in the network
are not 0 was broken. Fix this by explicitly normalizing the netwok
according to the bitmask.
Also add tests for these cases.
Fixes#6179. Thanks to @jonasschnelli for reporting and initial fix.
Don't clear `stopRequested` and `stopWhenEmpty` at the top of
`serviceQueue`, as this results in a race condition: on systems under
heavy load, some of the threads only get scheduled on the CPU when the
other threads have already finished their work. This causes the flags to
be cleared post-hoc and thus those threads to wait forever.
The potential drawback of this change is that the scheduler cannot be
restarted after being stopped (an explicit reset would be needed), but
we don't use this functionality anyway.
Most people expect a value of 1 to enable all for command line arguments.
However to do this for the -debug option you must type "-debug=".
This has been changed to allow "-debug=1" as well as "-debug=" to
enable all debug logging
To protect privacy, do not use UPNP when a proxy is set. The user may
still specify -listen=1 to listen locally (for a hidden service), so
don't rely on this happening through -listen.
Fixes#2927.
On a busy or slow system, the CScheduler unit test could fail because it
assumed all threads would be done after a couple of milliseconds.
Replace the hard-coded sleep with CScheduler stop() method that
will cleanly exit the servicing threads when all tasks are completely
finished.
Previously this was cleared only after UnlinkPrunedFiles, but it should really be cleared after FindFilesToPrune, regardless of whether there are any files to be pruned.
86a5f4b Relocate calls to CheckDiskSpace (Alex Morcos)
67708ac Write block index more frequently than cache flushes (Pieter Wuille)
b3ed423 Cache tweak and logging improvements (Pieter Wuille)
fc684ad Use accurate memory for flushing decisions (Pieter Wuille)
046392d Keep track of memory usage in CCoinsViewCache (Pieter Wuille)
540629c Add memusage.h (Pieter Wuille)
8f0947b Increase timeouts in pruning.py and modify warning language. (Alex Morcos)
b89f307 Fix incorrect variable name in FindFilesToPrune (Suhas Daftuar)
This assertion will occur any time that the client quits without
shutting down properly due to an error condition. As the user will
report this error instead of the error that was the root cause, it is
better to remove it.
Create a monitoring task that counts how many blocks have been found in the last four hours.
If very few or too many have been found, an alert is triggered.
"Very few" and "too many" are set based on a false positive rate of once every fifty years of constant running with constant hashing power, which works out to getting 5 or fewer or 48 or more blocks in four hours (instead of the average of 24).
Only one alert per day is triggered, so if you get disconnected from the network (or are being Sybil'ed) -alertnotify will be triggered after 3.5 hours but you won't get another -alertnotify for 24 hours.
Tested with a new unit test and by running on the main network with -debug=partitioncheck
Run test/test_bitcoin --log_level=message to see the alert messages:
WARNING: check your network connection, 3 blocks received in the last 4 hours (24 expected)
WARNING: abnormally high number of blocks generated, 60 blocks received in the last 4 hours (24 expected)
The -debug=partitioncheck debug.log messages look like:
ThreadPartitionCheck : Found 22 blocks in the last 4 hours
ThreadPartitionCheck : likelihood: 0.0777702
ca5f688 [QT] don't colorize icons on win and mac (Jonas Schnelli)
7247d10 [QT] use alert icon with tooltip insted of "(out of sync)" text (Jonas Schnelli)
51c7c70 [QT] remove frame to avoid double-frame situation in sendcoinsentry.ui (Jonas Schnelli)
2a6b844 [QT] change transaction amount and height in overview page (Jonas Schnelli)
Instead of only checking height to decide whether to disable script checks,
actually check whether a block is an ancestor of a checkpoint, up to which
headers have been validated. This means that we don't have to prevent
accepting a side branch anymore - it will be safe, just less fast to
do.
We still need to prevent being fed a multitude of low-difficulty headers
filling up our memory. The mechanism for that is unchanged for now: once
a checkpoint is reached with headers, no headers chain branching off before
that point are allowed anymore.
This class groups transactions that have been confirmed in blocks into buckets, based on either their fee or their priority. Then for each bucket, the class calculates what percentage of the transactions were confirmed within various numbers of blocks. It does this by keeping an exponentially decaying moving history for each bucket and confirm block count of the percentage of transactions in that bucket that were confirmed within that number of blocks.
-Eliminate txs which didn't have all inputs available at entry from fee/pri calcs
-Add dynamic breakpoints and tracking of confirmation delays in mempool transactions
-Remove old CMinerPolicyEstimator and CBlockAverage code
-New smartfees.py
-Pass a flag to the estimation code, using IsInitialBlockDownload as a proxy for when we are still catching up and we shouldn't be counting how many blocks it takes for transactions to be included.
-Add a policyestimator unit test
We don't want to erase orphans that still have missing inputs, they should still be tracked as orphans. Also, the transaction thats being accepted can't be an orphan otherwise it would have previously been accepted, so doesn't need to be added to the erase queue.
When the internal miner is enabled at the start of a new node, there
is an near instant assert in TestBlockValidity because its attempting
to mine a block before the top checkpoint.
Also avoids a data race around vNodes.
03c5687 appropriate response when trying to get a block in pruned mode (Jonas Schnelli)
1b2e555 add autoprune information to RPC "getblockchaininfo" (Jonas Schnelli)
a8cdaf5 checkpoints: move the checkpoints enable boolean into main (Cory Fields)
11982d3 checkpoints: Decouple checkpoints from Params (Cory Fields)
6996823 checkpoints: make checkpoints a member of CChainParams (Cory Fields)
9f13a10 checkpoints: store mapCheckpoints in CCheckpointData rather than a pointer (Cory Fields)
a71ab10 QA: add RPC tests for error reporting of "signrawtransaction" (dexX7)
8ac2a4e RPC: show script verification errors in "signrawtransaction" result (dexX7)
If there are any script verification errors, when using "signrawtransaction", they are shown in the RPC result:
```
// ...
Result:
{
"hex" : "value", (string) The hex-encoded raw transaction with signature(s)
"complete" : true|false, (boolean) If the transaction has a complete set of signatures
"errors" : [ (json array of objects) Script verification errors (if there are any)
{
"txid" : "hash", (string) The hash of the referenced, previous transaction
"vout" : n, (numeric) The index of the output to spent and used as input
"scriptSig" : "hex", (string) The hex-encoded signature script
"sequence" : n, (numeric) Script sequence number
"error" : "text" (string) Verification or signing error related to the input
}
,...
]
}
```
Connecting the chain can take quite a while.
All the while it is still showing `Loading wallet...`.
Add an init message to inform the user what is happening.
libsecp256k1's API changed, so update key.cpp to use it.
Libsecp256k1 now has explicit context objects, which makes it completely thread-safe.
In turn, keep an explicit context object in key.cpp, which is explicitly initialized
destroyed. This is not really pretty now, but it's more efficient than the static
initialized object in key.cpp (which made for example bitcoin-tx slow, as for most of
its calls, libsecp256k1 wasn't actually needed).
This also brings in the new blinding support in libsecp256k1. By passing in a random
seed, temporary variables during the elliptic curve computations are altered, in such
a way that if an attacker does not know the blind, observing the internal operations
leaks less information about the keys used. This was implemented by Greg Maxwell.
bba2216 RPC test for "#5418 Report missing inputs in sendrawtransaction" (Jonas Schnelli)
de8e801 Report missing inputs in sendrawtransaction (Pieter Wuille)
Compute the change directly as difference between the "requested" and
the actual value returned by SelectCoins. This removes a duplication of
the fee logic code.
Use a probabilistic bloom filter to keep track of which addresses
we think we have given our peers, instead of a list.
This uses much less memory, at the cost of sometimes failing to
relay an address to a peer-- worst case if the bloom filter happens
to be as full as it gets, 1-in-1,000.
Measured memory usage of a full mruset setAddrKnown: 650Kbytes
Constant memory usage of CRollingBloomFilter addrKnown: 37Kbytes.
This will also help heap fragmentation, because the 37K of storage
is allocated when a CNode is created (when a connection to a peer
is established) and then there is no per-item-remembered memory
allocation.
I plan on testing by restarting a full node with an empty peers.dat,
running a while with -debug=addrman and -debug=net, and making sure
that the 'addr' message traffic out is reasonable.
(suggestions for better tests welcome)
For when you need to keep track of the last N items
you've seen, and can tolerate some false-positives.
Rebased-by: Pieter Wuille <pieter.wuille@gmail.com>
1ec900a Remove broken+useless lock/unlock log prints (Matt Corallo)
352ed22 Add merkle blocks test (Matt Corallo)
59ed61b Add RPC call to generate and verify merkle blocks (Matt Corallo)
30da90d Add CMerkleBlock constructor for tx set + block and an empty one (Matt Corallo)
This commit adds several tests to the script_invalid.json data which
exercise some edge conditions that are not currently being tested.
These are mainly being added to cover several cases a branch coverage
analysis of btcd showed are not already being covered, but given more
tests of edge conditions are always a good thing, I'm contributing
them upstream.
The test which is intended to prove that the script engine is properly
rejecting non-minimally encoded PUSHDATA4 data is using the wrong
opcode and value. The test is using 0x4f, which is OP_1NEGATE instead
of the desired 0x4e, which is OP_PUSHDATA4. Further, the push of data
is intended to be 256 bytes, but the value the test is using is
0x00100000 (4096), instead of the desired 0x00010000 (256).
This commit fixes both issues.
This was found while examining the branch coverage in btcd against only
these tests to help find missing branch coverage.
This adds a -prune=N option to bitcoind, which if set to N>0 will enable block
file pruning. When pruning is enabled, block and undo files will be deleted to
try to keep total space used by those files to below the prune target (N, in
MB) specified by the user, subject to some constraints:
- The last 288 blocks on the main chain are always kept (MIN_BLOCKS_TO_KEEP),
- N must be at least 550MB (chosen as a value for the target that could
reasonably be met, with some assumptions about block sizes, orphan rates,
etc; see comment in main.h),
- No blocks are pruned until chainActive is at least 100,000 blocks long (on
mainnet; defined separately for mainnet, testnet, and regtest in chainparams
as nPruneAfterHeight).
This unsets NODE_NETWORK if pruning is enabled.
Also included is an RPC test for pruning (pruning.py).
Thanks to @rdponticelli for earlier work on this feature; this is based in
part off that work.
has parts of @mhearn #4351
* allows querying the utxos over REST
* same binary input and outputs as mentioned in Bip64
* input format = output format
* various rpc/rest regtests
Ever since #5957 there has been the problem that older RPC test cases
(as can be found plenty in open pulls) use setgenerate() on regtest,
assuming a different interpretation of the arguments. Directly
generating a number of blocks has been split off into a new method
`generate` - however using `setgenerate` with the previous arguments will
result in spawning an unreasonable number of threads, and well, simply
not work as expected without clear indication of the error.
Add an error to point the user at the right method.
It's reasonable that automatic coin selection will not pick a zero
value txout, but they're actually spendable; and you should know
if you have them. Listing also makes them available to tools like
dust-b-gone.
