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tarcmd tests: the passthrough filter is written once, before any child - #69
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TestCompressProgram wrote its filter script and ran it through tar's -I in the same test, in parallel with tests that run zstdmt, unzstd and the system tar. A child forked by one of those between the script's open and close inherits the write descriptor until its exec, and running the script in that window fails with "text file busy" (golang/go#22315); the verify lane met it on ubuntu-24.04-arm and passed on a rerun. TestMain now writes the script before any test runs, with no child alive, and the test runs it. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> Signed-off-by: closer-claudio <claudio@farcloser.world>
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November 10, 2026 05:46
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🎯 Why
TestCompressProgramfailed once on #67 verify lane, ubuntu-24.04-arm (https://github.com/forkcloser/compress/actions/runs/42761685321/job/129648982339):tar: …/passthrough: Cannot run: text file busy, then passed on a rerun. The test wrote its filter script and ran it through-Iwhile parallel tests in the package forkzstdmt,unzstdand the system tar.forkcopies every descriptor, close-on-exec ones included, and a child between fork and exec holds the script's write descriptor until its exec; the kernel refuses to exec a file open for writing (golang/go#22315,os/execdoes not retry).🛠️ What
internal/tarcmd/run_test.go: aTestMainwrites the passthrough script once, beforem.Run, into a temporary directory removed afterwards;TestCompressProgramruns that script and writes nothing executable. The window is closed by construction: the script's write descriptor is closed before the test process forks for the first time, so no child can inherit it.🧪 How
V: the tarcmd package and
just test(273 tests) green,just lintgreen. V: Go's test wrapper passesm.Run's result toos.ExitwhenTestMainreturns (testing.go), so no explicit exit. U: the race is not reproducible on demand; the argument is structural.