[MarcZX10]

Fixes #5279.

What

A Windows host stream can resume reading after EOF when another handle appends bytes, while FreeBSD keeps returning EOF until clearerr, a seek, or ungetc. Keep the guest stream’s EOF behavior consistent across fgetc, fgets, fread, and fscanf, including the EOF return rules for formats that do or do not require input. The regression covers the reported append-after-EOF sequence and scanner format cases.

The change carries Hussein Kadhim’s reviewed fix commits with his original commit authorship preserved. The known %n-leading format limitation remains recorded in TechnicalDebt.md.

Tested

• Linux, GCC 12.2, Release: guest_standard_streams and file_streams passed (2/2).
• tools/check_conventions.py --base upstream/main passed.
• Windows-specific test matrix from the issue was not rerun locally.

Checklist

• Based on current main; no other open PR implements the same functions
• One topic per PR; follow-ups go in a new PR
• No comments in code except technical debt
• Unimplemented-path policy: not applicable; no new unimplemented path
• No notes, investigation files, or images added
• No third-party code added
• Generic behavior, not title-specific
• Depends on: none
• Unblocks: none identified in libc: reads after end-of-file return newly appended data on Windows, where FreeBSD keeps returning EOF until clearerr; fix branch ready #5279
• GPUs tested: n/a
• AI-assisted: yes

[github-actions]

Other open pull requests touch the same code. Merging one will break the other, or both implement the same thing. If this one builds on them, list them in Depends on.

Pull request	Conflicting files (lines on main)	Same exports	Same new files
#4627	core/libs/prx/libc/src/StandardStreams.cpp L42

[MarcZX10]

Closing this duplicate: it carries the same EOF-sticky implementation already reviewed in #5330 (and #5222). The maintainer closed #5330 because no title-specific failure was identified and asked contributors to hold generic PRs while the queue is high. I should have found that history before opening this PR.