lib: add taproot support to libconsensus

[brunoerg]

Grabbed from #21158. Closes #21133.

[DrahtBot]

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Type	Reviewers
ACK	theStack, achow101, darosior

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #28438 (Use serialization parameters for CTransaction by ajtowns)

If you consider this pull request important, please also help to review the conflicting pull requests. Ideally, start with the one that should be merged first.

[fanquake]

cc @darosior

[darosior]

Yay, concept ACK. Thanks for picking this up. Do you plan to address #21158 (comment)? Is this why you opened this as a draft?

[brunoerg]

Yay, concept ACK. Thanks for picking this up. Do you plan to address #21158 (comment)? Is this why you opened this as a draft?

Yes!

[brunoerg]

Ready for review!

[brunoerg]

Force-pushed addressing #28539 (comment) and changed the type of value in UTXO struct to int64_t.

[brunoerg]

Addressed #28539 (comment)

[brunoerg]

Force-pushed addressing:

• lib: add taproot support to libconsensus #28539 (comment)
• lib: add taproot support to libconsensus #28539 (comment)
• lib: add taproot support to libconsensus #28539 (comment)

[brunoerg]

CI failure seems unrelated:

Reading package lists...
Building dependency tree...
Reading state information...
E: Unable to locate package linux-headers-6.2.0-32-generic
E: Couldn't find any package by glob 'linux-headers-6.2.0-32-generic'
E: Couldn't find any package by regex 'linux-headers-6.2.0-32-generic'
Retries exhausted
Error: building at STEP "RUN bash -c cd /ci_container_base/ && set -o errexit && source ./ci/test/00_setup_env.sh && ./ci/test/01_base_install.sh": while running runtime: exit status 100

Exit status: 100

[maflcko]

Jup, this particular CI failure can be ignored. It should also fix itself on the next push.

[brunoerg]

Force-pushed: rebased and addressed #28539 (comment).

[theStack]

ACK ff8e2fc

Some follow-up thoughts: on the long-term, I think it would be very nice to have a test that interacts with the libbitcoinconsensus shared library (i.e. .so/.dylib/.dll file, depending on the OS used). This should be doable in form of a functional test without any extra dependencies using Python's ctypes module, IIUC: https://docs.python.org/3/library/ctypes.html

However, I didn't manage to even build a shared library so far. Do we still support this in the build system? ./configure --enable-shared doesn't do anything on my side (tested on Ubuntu 22.04), I keep getting checking whether to build shared libraries... no from the configure script.

[achow101]

ACK ff8e2fc

[darosior]

re-ACK ff8e2fc

[fanquake]

Probably better to use the actual PR number next time?

[panicfarm]

A naive question (I am a Rust developer, not a C++ Core dev): taproot soft fork has been in the bitcoin core code since 0.22. But even at the 0.25 release, libconsensus still does not have taproot support. Isn't libconsensus compiled from the same source as the core binary itself, albeit as a shared library? If this is so, I am confused why it has not had taproot support since 0.22?

[sipa]

@panicfarm libconsensus had certainly contained all the logic for taproot validation ever since Bitcoin Core had it, but it was not exposed through the library interface, for two reasons:

• The API requires passing in flags to select which softfork rules to apply to validation. No such flag was exposed for taproot.
• Taproot validation requires access to more information that wasn't present in the libconsensus API (specifically, the UTXO data of all spent UTXOs by a transaction). New functions were needed that allow passing in this information.