FreeBSD 11 fopen opens the path with _open, and vn_open_vnode refuses a
directory only for FWRITE or O_TRUNC, so fopen of a directory in a read
mode succeeds; Linux hosts already open it. On Windows CreateFileW
without FILE_FLAG_BACKUP_SEMANTICS refused it with EACCES.
fopen now opens such a path as a libkernel directory descriptor, which
libkernel registers in libc when it loads, and fclose and freopen remove
it from libkernel's table. Reads on the stream fail with EISDIR and set
the error indicator, as on a Linux host and FreeBSD's tmpfs: the Windows
CRT fails them already but reports EINVAL. Writes fail with EBADF, and
fseek, ftell and ungetc work, as on any read-only stream.
On Windows, freopen reopened a stream through _wfreopen, which opens the file without FILE_SHARE_DELETE, so remove or rename of the file failed while the stream was open, unlike fopen streams and POSIX unlink/rename of an open file. freopen now closes the previous stream and opens the new file through the same CreateFileW path fopen uses, so the reopened stream shares delete access. Host standard streams and an empty filename keep the _wfreopen path. Reference: FreeBSD 11 unlink(2) and rename(2) succeed on a file that is open.
On Windows the UCRT does not switch an r+, w+ or a+ stream from writing
to reading without fflush or fseek: fread after fwrite returned bytes of
the write buffer and the next flush wrote them over the file, and ungetc
failed on an update stream that was not already reading. On Linux glibc
does not switch either for ungetc, which pushes the byte back over the
pending write, drops the write and can corrupt the heap on the next read,
or for an fread of at least the buffer size, which drops the write and
reads from the old offset.
fread, fgetc, getc_unlocked, fgets, ungetc, ungetwc and fscanf now flush
pending output and mark the stream as reading first, as FreeBSD 11.4's
__srefill and __ungetc do, through _IO_switch_to_get_mode on glibc.
Writes directly after reads still go through the UCRT on Windows; the
gap is recorded in the libc technical debt.
fopen resolved the random device paths to a host file that does not
exist and failed with ENOENT, while open and sceKernelOpen already serve
them from host entropy. A read-only fopen of either path now returns a
stream whose fread fills the buffer with host entropy. setvbuf, feof,
ferror, clearerr, the stream locks and fclose work on it, fflush returns
0 as on a FreeBSD stream that is not writing, other stream functions
throw, and opening the paths for writing throws as in libkernel.
ProsperoTV (PPSA99003) reads its phone pairing code this way and showed
"Code expired or unavailable".
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
On Linux a guest stderr redirect also moves the host's: guest
descriptors are host descriptors, and the guest stderr stream wraps the
host stderr FILE. After dup2(fd, 2), or freopen(path, mode, stderr) with
full buffering, the libc terminate report, the host fprintf(stderr)
diagnostics and libstdc++'s terminate message go into the title's pipe
or file, and abort() discards what is still buffered. RetroArch
(PPSA99169) reopens stderr onto app0/trace.txt with full buffering, so
its stop on main left no message anywhere.
Before the first guest redirect of descriptor 2 (libkernel dup2, libc
freopen of a stream on descriptor 2), keep a close-on-exec duplicate of
the host descriptor 2 and point the host stderr at an unbuffered stream
on it. The guest stream keeps its own FILE and follows the redirect.
The libc terminate report writes to the kept descriptor with write()
instead of the stderr stream, and libkernel's sceKernelDebugOutText uses
the same kept descriptor.
The guest fgets handed the size straight to the host. With a size of 0
glibc and the Windows runtime return NULL without setting errno or the
stream error indicator, and a negative size goes to the Windows
invalid-parameter path. FreeBSD's fgets checks n <= 0 before reading:
it sets __SERR on the stream, sets errno to EINVAL and returns NULL,
leaving the buffer and the file position untouched.
fgets_nid_postfix now does the same before calling the host. The
FileStream flag it uses was only set for encoding errors so far and is
renamed from SetEncodingError/encodingError to SetError/guestError; it
already stays set until clearerr like __SERR.
guest_standard_streams checks sizes 0, -1 and INT_MIN (NULL, errno 22,
error indicator set and cleared by clearerr, buffer and position
untouched) and that a following read still returns the line; it fails
without the change.
Fixes#3084
AI-assisted: yes
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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>
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