coreutils stdbuf: fix cross-compilation

Commit 2:

Summary:

Partial fix for https://github.com/uutils/coreutils/issues/6591

The current code declare libstdbuf as a build-dependency of stdbuf as a workaround to enforce that libstdbuf is compiled before stdbuf. This breaks cross-compilation, because build-dependencies were compiled for the host architecture, and not for the target architecture.

The reason this workaround is necessary is that bindeps is available only in nightly at the moment: https://rust-lang.github.io/rfcs/3028-cargo-binary-dependencies.html

This commit replaces the "build-dependency" workaround with another workaround: calling cargo manually to build libstdbuf in the build.rs of stdbuf, in order to ensure that libstdbuf is built before stdbuf.

Changes:

Removed cpp/cpp_build dependencies:

The cpp, cpp_build, and related dependencies were removed because they made cross-compilation in a build.rs file >very complex, since you need to pass proper CXX env variables for cross-compilation, whereas cross-compiling rust code using cargo is quite simple. Provided Rust implementations for getting stdin, stdout, and stderr pointers. Switched from C++/cpp macro-based initialization to using the Rust ctor crate for library initialization.

Remove "feat_require_crate_cpp" which is not needed any more, since stdbuf was the only utility using the cpp crate.

Tests:

This commit fixes this test: cross test --target aarch64-unknown-linux-gnu --features stdbuf test_stdbuf::test_libstdbuf_preload -- --nocapture

The "i686" build of stdbuf was also broken (stdbuf 32 bits, but libstdbuf 64 bits) and test_stdbuf::test_libstdbuf_preload >of the i686 builds in github CI serves as regression test for this issue, no need to add a cross-rs test for aarch64.

Commit 1:

stdbuf: add test_libstdbuf_preload

This test verifies that stdbuf correctly preloads libstdbuf and that there is no architecture mismatch error. At the moment the test passes when compiled natively, but fails when compiled with cross-rs, due to https://github.com/uutils/coreutils/issues/6591

This passes:
cargo test --features stdbuf test_stdbuf::test_setvbuf_resolution -- --nocapture
This fails:
cross test --target aarch64-unknown-linux-gnu --features stdbuf test_stdbuf::test_libstdbuf_preoad -- --nocapture

May 22 '25 20:05 Ecordonnier

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)

May 22 '25 21:05 github-actions[bot]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/stdbuf (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

May 23 '25 20:05 github-actions[bot]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/stdbuf (passes in this run but fails in the 'main' branch)

May 23 '25 22:05 github-actions[bot]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/tail/inotify-dir-recreate (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)

May 24 '25 21:05 github-actions[bot]

GNU testsuite comparison:

Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)

May 24 '25 23:05 github-actions[bot]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)

May 25 '25 07:05 github-actions[bot]

GNU testsuite comparison:

Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)

May 25 '25 08:05 github-actions[bot]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/inotify-dir-recreate (passes in this run but fails in the 'main' branch)

May 25 '25 10:05 github-actions[bot]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)

May 25 '25 20:05 github-actions[bot]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)

May 25 '25 21:05 github-actions[bot]

@sylvestre the branch should be ready for review. There is some intermittent issue with the CI jobs not related to the branch, but everything except cargo-deny was green before my latest rebase. My last commit fixes the cargo-deny error.

May 26 '25 09:05 Ecordonnier

GNU testsuite comparison:

Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)

May 28 '25 09:05 github-actions[bot]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)

May 29 '25 10:05 github-actions[bot]

GNU testsuite comparison:

Skip an intermittent issue tests/misc/tee (fails in this run but passes in the 'main' branch)

May 30 '25 11:05 github-actions[bot]

GNU testsuite comparison:

Skipping an intermittent issue tests/misc/tee (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)

Jun 02 '25 09:06 github-actions[bot]

I am not very happy with the command but I don't have a better solution to propose. Let's see if it sticks.

Jun 02 '25 11:06 sylvestre