Bitcoin Core

kernel: Add chain params context option to C header

As a first option, add the chainparams. For now these can only be
instantiated with default values. In future they may be expanded to take
their own options for regtest and signet configurations.

This commit also introduces a unique pattern for setting the option
values when calling the `*_set(...)` function.

kernel: Add kernel library context object

The context introduced here holds the objects that will be required for
running validation tasks, such as the chosen chain parameters, callbacks
for validation events, and interrupt handling. These will be used by the
chainstate manager introduced in subsequent commits.

This commit also introduces conventions for defining option objects. A
common pattern throughout the C header will be:
```
options = object_option_create();
object = object_create(options);
```
This allows for more consistent usage of a "builder pattern" for
objects where options can be configured independently from
instantiation.

kernel: Add logging to kernel library C header

Exposing logging in the kernel library allows users to follow
operations. Users of the C header can use
`kernel_logging_connection_create(...)` to pass a callback function to
Bitcoin Core's internal logger. Additionally the level and category can
be globally configured.

By default, the logger buffers messages until
`kernel_loggin_connection_create(...)` is called. If the user does not
want any logging messages, it is recommended that
`kernel_disable_logging()` is called, which permanently disables the
logging and any buffering of messages.

Co-authored-by: stringintech <stringintech@gmail.com>

kernel: Introduce initial kernel C header API

As a first step, implement the equivalent of what was implemented in the
now deprecated libbitcoinconsensus header. Also add a test binary to
exercise the header and library.

Unlike the deprecated libbitcoinconsensus the kernel library can now use
the hardware-accelerated sha256 implementations thanks for its
statically-initialzed context. The functions kept around for
backwards-compatibility in the libbitcoinconsensus header are not ported
over. As a new header, it should not be burdened by previous
implementations. Also add a new error code for handling invalid flag
combinations, which would otherwise cause a crash.

The macros used in the new C header were adapted from the libsecp256k1
header.

To make use of the C header from C++ code, a C++ header is also
introduced for wrapping the C header. This makes it safer and easier to
use from C++ code.

Co-authored-by: stickies-v <stickies-v@protonmail.com>

qt: Modernize custom filtering

In `QSortFilterProxyModel`, `invalidateFilter()` is scheduled for
deprecation in Qt 6.13.
`beginFilterChange()` was introduced in Qt 6.9.
`endFilterChange()` was introduced in Qt 6.10.

depends: disable builtin variables

depends: disable builtin rules and suffixes.

When there is no rule to build a target in the makefile, make looks
for a builtin rule.
When --no-builtin-rules is specified make no longer performs this lookup.

E.g. the following in an excerpt from make -d output.
Here, make looks for a rule to build 'all'.

Considering target file 'all'.
File 'all' does not exist.
Looking for an implicit rule for 'all'.
Trying pattern rule with stem 'all'.
Trying implicit prerequisite 'all.o'.
Trying pattern rule with stem 'all'.
Trying implicit prerequisite 'all.c'.
Trying pattern rule with stem 'all'.
Trying implicit prerequisite 'all.cc'.
Trying pattern rule with stem 'all'.
Trying implicit prerequisite 'all.C'.
Trying pattern rule with stem 'all'.
Trying implicit prerequisite 'all.cpp'.
Trying pattern rule with stem 'all'.
Trying implicit prerequisite 'all.p'.
Trying pattern rule with stem 'all'.
Trying implicit prerequisite 'all.f'.
...
Many more lines like this are omitted.

Because this build system does not use make builtin rules or suffixes,
there is no benefit in having builtin rules enabled.

There are 2 benefits in having builtin rules disabled.

1. Improves performance by eliminating redundant lookups.
2. Simplifies troubleshooting by reducing the output of make -d or
make -p.

ci: fix configure docker action inputs

The options used were wrong in two ways: firstly they were not enforced
as a "choice" (i.e. invalid input valudes could be provided without
error) and one of the options was listed as `gh` when we passed it as
`gha` from ci.yml.

"Fix" this by removing the choice altogether but sanity-testing the
input value against an expected list using a GHA "warning" to notify of
unknown inputs.

refactor: Prefer `<=>` over multiple relational operators

Define `operator<=>` in classes that have all of `<`, `<=`, `>`, `>=`.

refactor: Remove all `operator!=` definitions

The compiler can deduce `operator!=` from `operator==`.

refactor: remove dead branches in `SingletonClusterImpl`

`SplitAll()` always calls `ApplyRemovals()` first, for a singleton, it empties the cluster, therefore any `SingletonClusterImpl` passed to `Split()` must be empty.

`TxGraphImpl::ApplyDependencies()` first merges each dependency group and asserts the group has at least one dependency.
Since `parent` != `child`, `TxGraphImpl::Merge()` upgrades the merge target to `GenericClusterImpl`, therefore the `ApplyDependencies()` is never dispatched to `SingletonClusterImpl`.

Found during review: https://github.com/bitcoin/bitcoin/pull/33157#discussion_r2423058928
Coverage evidence:
* https://maflcko.github.io/b-c-cov/fuzz.coverage/src/txgraph.cpp.gcov.html#L1446
* https://storage.googleapis.com/oss-fuzz-coverage/bitcoin-core/reports/20251103/linux/src/bitcoin-core/src/txgraph.cpp.html#L1446

refactor: Use initializer list in CompressedHeader

Also mark CompressedHeader as explicit, and GetFullHeader as const

Co-Authored-By: Aurèle Oulès <aurele@oules.com>

refactor: Remove unused parameter in ReportHeadersPresync

Co-Authored-By: Aurèle Oulès <aurele@oules.com>

refactor: Remove redundant parameter from CheckHeadersPoW

No need to pass consensusParams, as CheckHeadersPoW already has access
to m_chainparams.GetConsensus()

Co-Authored-By: maflcko <6399679+maflcko@users.noreply.github.com>

refactor: Remove useless CBlock::GetBlockHeader

There is no need for a function to convert a CBlock to a CBlockHeader, as it's a child
class of it.

refactor: Use std::span in HasValidProofOfWork

Co-Authored-By: Pieter Wuille <pieter@wuille.net>

refactor: Compute work from headers without CBlockIndex

Avoid the need to construct a CBlockIndex object just to compute work for a header,
when its nBits value suffices for that.

Co-Authored-By: Pieter Wuille <pieter@wuille.net>

p2p: Avoid an IsAncestorOfBestHeaderOrTip call

Just don't call this function when it won't have any effect.

Note that we can't remove the LookupBlockIndex call, since `last_received_header`
is needed to check if new headers were received (`received_new_header`).

validation: don't reallocate cache for short-lived CCoinsViewCache

A few temporary `CCoinsViewCache`'s are destructed right after the `Flush()`, therefore it is not necessary to call `ReallocateCache` to recreate them right before they're killed anyway.

* `Flush()` - retains existing functionality;
* `Flush(/*will_reuse_cache=*/false)` - skips destruction and reallocation of the parent cache since it will soon go out of scope anyway;

For the `will_reuse_cache` parameter we want to see exactly which ones will reallocate memory and which won't - since both can be valid usages.

This change was based on a subset of https://github.com/bitcoin/bitcoin/pull/28945.

Co-authored-by: Martin Ankerl <martin.ankerl@gmail.com>

coins: reduce lookups in dbcache layer propagation

Previously, when the parent coins cache had no entry and the child did, `BatchWrite` performed a find followed by `try_emplace`, which resulted in multiple `SipHash` computations and bucket traversals on the common insert path.

This change uses a single leading `try_emplace` and branches on the returned `inserted` flag.
In the `FRESH && SPENT` case (only exercised by tests), we erase the just-inserted placeholder (which is constant time with no rehash anyway).
Semantics are unchanged for all valid parent/child state combinations.

This change is a minimal version of https://github.com/bitcoin/bitcoin/pull/32128/commits/723c49b63bb10da843fbb6efc6928dca415cc47f and draws simplification ideas https://github.com/bitcoin/bitcoin/pull/30673/commits/ae76ec7bcff0a08a61f294882a71e46d177b009f.

Added TODO versions for related pre-existing issues that should be fixed in follow-ups.

Co-authored-by: Martin Ankerl <martin.ankerl@gmail.com>
Co-authored-by: Andrew Toth <andrewstoth@gmail.com>
Co-authored-by: optout <13562139+optout21@users.noreply.github.com>

Add eclipse, partitioning, and fingerprinting note to i2p.md

Also introduced a Privacy Recommendations section to docs.

init: Require explicit -asmap filename

Currently, if `-asmap` is specified without a filename, bitcoind tries to load
`ip_asn.map` data file.

This change now requires `-asmap=ip_asn.map` or another filename to be
specified explicitly.

The change is intended to make behavior of the option explicit avoid confusion
reported https://github.com/bitcoin/bitcoin/issues/33386 where documentation
specifies a default file which is not actually loaded by default. It was
originally implemented in
https://github.com/bitcoin/bitcoin/pull/33631#issuecomment-3410302383 and
various alternatives are discussed there.

Co-authored-by: Fabian Jahr <fjahr@protonmail.com>

test: Format strings in `*.rs`

`format!` strings may contain variables within the string
representation. This is a lint as of a recent `rustc` nightly version.

ci: gha: Set debug_pull_request_number_str annotation

test: clarify submitBlock() mutates the template

PR #33374 proposed a new Mining IPC method applySolution() which
could be used by clients to obtain the reconstructed block for
inspection, especially in the case of a rejected block.

However it was pointed out during review that submitBlock() modified
the template CBlock in place, so the client can just call getBlock()
and no new method is needed.

This commit adds a test to document that (now intentional) behavior.