fcntl and sceKernelFcntl answered EBADF (sceKernelFcntl threw) for
every descriptor outside the libSceNet socket table, so files, pipes,
directories and descriptors 0 to 2 could not be queried or changed.
Observed: Yamagi Quake II (PPSA99007) stops with
"Sys_Error: change stdin to blocking Bad file descriptor", from
fcntl(fileno(stdin), F_SETFL, fcntl(0, F_GETFL, 0) & ~FNDELAY)
(yquake2 src/backends/unix/system.c:81-86).
Predicted from the titles' sources and decoded call sites: XPSemu
(PPSA97358, 97 fcntl sites: F_GETFD 12, F_SETFD 20, F_GETFL 8,
F_SETFL 9, F_DUPFD 1, F_DUPFD_CLOEXEC 7, F_GETLK 9) fails in
qemu_init_main_loop, where its pipe2 (pipe plus F_SETFD FD_CLOEXEC) and
glib's g_unix_set_fd_nonblocking (F_GETFL, F_SETFL) build the event
notifier (util/event_notifier-posix.c:44-67); VLC (PPSA85300, 43 sites,
F_RDAHEAD on every file it opens), RetroArch (PPSA99169, 17),
Porpoise (PPSA99764, 13) and Ruffle (9) call it on files and pipes.
The commands follow FreeBSD 11.4 kern_fcntl and kern_dup
(sys/kern/kern_descrip.c:479-799, 812, release/11.4.0 8c639945):
F_GETFD/F_SETFD keep the close-on-exec flag per descriptor, F_GETFL
reports the host access mode with the status flags, F_SETFL changes
only O_NONBLOCK, O_APPEND, O_ASYNC, O_FSYNC, O_DIRECT and FRDAHEAD,
F_DUPFD/F_DUPFD_CLOEXEC give the lowest free descriptor at or above the
start through dup (EINVAL for a negative start), F_DUP2FD goes through
dup2, F_RDAHEAD/F_READAHEAD set FRDAHEAD on files (EBADF on pipes,
ENOTTY elsewhere), and unknown commands fail with EINVAL. Status flags
live in a guest table shared by dup, dup2 and F_DUPFD like an open file
description. O_NONBLOCK switches a pipe (PIPE_NOWAIT on Windows, where an
empty read and a full write now report EAGAIN; the host flag on Linux).
Record locks use the host POSIX locks on Linux and throw on Windows.
Changes the host cannot model throw naming the flag and descriptor kind.
Sockets keep their path unchanged.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
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