[wip,nomerge,rfc] build: Require C++23 compiler #36033

C++23 for Bitcoin Core is mostly a "style update" on top of C++20. However, the workarounds to avoid C++23 keep accumulating and some parts of the code already use C++23 features, such as lambda attributes (https://github.com/bitcoin-core/libmultiprocess/commit/bdd0cd69418d189f62699d274a751cbf6d36bb43).

I don't know when it is fine to switch, but at some point, I think it is fine to require a C++23 compiler, so that new stuff is unlocked. Of course this requires bumping the minimum required compiler versions:

• GCC: 13
• Clang: 19

There are some C++23 features that aren't implemented (such as <stacktrace> not really shipped in any vanilla stdlib today), or e.g. ranges::starts_with not implemented until libstdc++-16. But overall I think we are better off using C++23 without those few features instead of waiting longer?

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Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/36033.

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Conflicts

Reviewers, this pull request conflicts with the following ones:

• #36160 (refactor: Minor improvements to HTTP unit tests by hodlinator)
• #36052 (ci: Doc: Move all config comments right next to the option they explain by maflcko)
• #36042 (build: Bump g++ minimum supported version to 13 by maflcko)
• #35998 (wallet: Handle or explicitly ignore WalletBatch write failures by achow101)
• #35752 (wallet: make encryption state updates atomic by l0rinc)
• #35445 (wallet, descriptor: Revert StringType::COMPAT for Miniscript expressions and drop the concept of a Descriptor ID that can be validated by achow101)
• #34909 (wallet, refactor: modularise wallet by extracting out legacy wallet migration by rkrux)
• #31507 (build: Use clang-cl to build on Windows natively by hebasto)

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.

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LLM Linter (✨ experimental)

Possible places where comparison-specific test macros should replace generic comparisons:

• [src/test/util_expected_tests.cpp] BOOST_CHECK_THROW((void)e.value(), std::bad_expected_access<std::string>); -> Prefer BOOST_CHECK_EXCEPTION with a predicate that checks the exception details, if available, instead of only asserting the generic exception type.
• [src/test/util_expected_tests.cpp] BOOST_CHECK_THROW(void_e.value(), std::bad_expected_access<std::string>); -> Prefer BOOST_CHECK_EXCEPTION with a predicate that checks the exception details, if available, instead of only asserting the generic exception type.

^{2026-08-24 14:55:56}

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🚧 At least one of the CI tasks failed. _{Task NetBSD Cross: https://github.com/bitcoin/bitcoin/actions/runs/32352184973/job/96373551351} _{LLM reason (✨ experimental): CI failed due to a C++ build error: std::ranges::views::zip is not available (no member named 'zip' in namespace 'std::ranges::views').}

<details><summary>Hints</summary>

Try to run the tests locally, according to the documentation. However, a CI failure may still happen due to a number of reasons, for example:

• Possibly due to a silent merge conflict (the changes in this pull request being incompatible with the current code in the target branch). If so, make sure to rebase on the latest commit of the target branch.

• A sanitizer issue, which can only be found by compiling with the sanitizer and running the affected test.

• An intermittent issue.

Leave a comment here, if you need help tracking down a confusing failure.

</details>

Concept ACK

edede385cab47020124bba6db98d69319168afb5

iwyu incorrectly suggests to remove the util/expected include

This looks like IWYU's "Automatic re-export: function return values" heuristics in action.