Use unlocked POSIX EOF/error queries after unlocked byte operations so status synchronization cannot reacquire the stream lock. Keep the verified UCRT status calls on Windows, and cover byte, status, error, and held-lock behavior.
Co-authored-by: MarcZX100 <marczxrr@gmail.com>
FreeBSD's setvbuf takes a zero size with _IOFBF or _IOLBF as "pick the
buffer size". The UCRT rejects sizes below 2 for those modes through
its invalid parameter handler, so the call failed on Windows and a test
process was terminated. A zero size now drops the given buffer and
asks the host for one of BUFSIZ bytes.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Romans Pokrovskis
MarcZX100
LeandroLP23
Nicolas Abosch
SamG-Coder