Today in POSIX surprises: `ln -f` is not *quite* atomic due to the combined semantics of link() and rename(); it racily uses a temp file and if the stars align might unlink() an identially-named temp file created by another process.
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but nothing ever seeded the RNG mkstemp() used, and closing the file and reopening it left a brief window during which another ar instance could land on the same temp file, which regularly resulted in corruption and build failures until I tracked down a patch fixing the issue
