build: replace header checks with `__has

fanquake commented at 3:31 pm on May 2, 2025: member

Replace the checks in CMake, with the equivalent functionality provided by the standard library (since C++17). See https://en.cppreference.com/w/cpp/preprocessor/include.

Guix Build:

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DrahtBot commented at 3:31 pm on May 2, 2025: contributor

The following sections might be updated with supplementary metadata relevant to reviewers and maintainers.

Code Coverage & Benchmarks

For details see: https://corecheck.dev/bitcoin/bitcoin/pulls/32405.

Reviews

See the guideline for information on the review process.

Type	Reviewers
ACK	shahsb, purpleKarrot
Concept ACK	hebasto
Approach ACK	TheCharlatan

If your review is incorrectly listed, please react with 👎 to this comment and the bot will ignore it on the next update.

Conflicts

Reviewers, this pull request conflicts with the following ones:

#31424 (build: enable libc++ hardening in debug builds by vasild)

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.

DrahtBot added the label Build system on May 2, 2025

build: replace header checks with __has_include

See https://en.cppreference.com/w/cpp/preprocessor/include.

e1f543823b

fanquake force-pushed on May 2, 2025

DrahtBot added the label CI failed on May 2, 2025

DrahtBot commented at 3:41 pm on May 2, 2025: contributor

🚧 At least one of the CI tasks failed. Task lint: https://github.com/bitcoin/bitcoin/runs/41550770562 LLM reason (✨ experimental): Lint check failed due to unnecessary include of bitcoin-build-config.h.

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.

hebasto commented at 4:06 pm on May 2, 2025: member

Concept ACK. This improves code locality.

DrahtBot removed the label CI failed on May 2, 2025

shahsb commented at 4:09 am on May 4, 2025: none

Concept ACK.

This improves code readability and simplicity. This is indeed a nice feature from portability and backward compatibility perspective. Thanks for making the changes!!

shahsb commented at 4:10 am on May 4, 2025: none

ACK https://github.com/bitcoin/bitcoin/pull/32405/commits/e1f543823b300b28c9edaf5d1a3e1e9badde471b

DrahtBot requested review from hebasto on May 4, 2025

purpleKarrot commented at 9:56 am on May 5, 2025: contributor

ACK e1f543823b300b28c9edaf5d1a3e1e9badde471b

Less code, less cmake cache variables, less error prone. However, I have concerns about the if-header-exists-then-include-it pattern, irrespective of the way the existence is checked (both check_include_file_cxx and __has_include). You don’t include a header because it exists, but because of the symbols it declares. The logic should be: If the platform is BAR, then include <foo.h> to use function foo and fail when it it does not exist. If not on platform BAR, then don’t include <foo.h>.

fanquake commented at 11:05 am on May 5, 2025: member

The logic should be: If the platform is BAR, then include <foo.h>

Not sure I agree here; as this would give us less-generic code, and the need to maintain platform mappings.

TheCharlatan commented at 11:18 am on May 5, 2025: contributor

Approach ACK e1f543823b300b28c9edaf5d1a3e1e9badde471b , pending guix build.

You don’t include a header because it exists, but because of the symbols it declares. The logic should be: If the platform is BAR, then include <foo.h> to use function foo and fail when it it does not exist. If not on platform BAR, then don’t include <foo.h>.

There is already some additional gating in the first instance (randomenv.cpp), which actually checks for the relevant gadgets (HAVE_SYSCTL). A similar gating in util/threadnames is not required, so I don’t see the need for additional platform mapping here.

build: replace header checks with __has_include #32405

Code Coverage & Benchmarks

Reviews

Conflicts

build: replace header checks with `__has_include` #32405