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>
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>
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>
Dean