The running-executable replacement test copied /bin/sleep under the
names "running" and "leftover" and started the copy. On Ubuntu 26.04
/bin/sleep is the uutils multi-call coreutils binary, which picks the
utility from the file name of the path it was started through, not
from argv[0], so the copy printed "coreutils: unknown program
'running'" and exited, and file_writer_binary and file_writer_text
failed without ever replacing a running executable. The test now
copies its own executable and starts it with a "wait" argument that
sleeps, so it no longer depends on how a system binary reads its name.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
A relink killed between writing <output>.tmp and renaming it left that
file behind, and every later relink of the output then fell back to the
in-place write, bringing back the failure on a running build. The
temporary file is now created under a new name beside the output with
O_CREAT | O_EXCL and the previous permission bits, and written through
that descriptor, so a file left by an earlier run never blocks a
replacement and is never touched.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
