per
https://pubs.opengroup.org/onlinepubs/9799919799/functions/posix_close.html
Add a flag value to fhandler_*::close() and close_with_arch() methods,
taking -1 as default argument, used to indicate default close(2)
behaviour.
The only fhandlers capable of returning EINTR are the INET based
socket fhandlers. Handle -1 and POSIX_CLOSE_RESTART equivalent,
making close() and posix_close(POSIX_CLOSE_RESTART) behaving
identically.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
The isclosed flag is only used in pipe and FIFO code, so move the
flag down into the fhandler_pipe_fifo class.
Note that such a flag is not sufficient to avoid evil, like closing
an already closing fhandler from another thread. If we ever need this,
it has to be implemented threadsafe.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
All three warnings produced with -Og are false positives.
But given we're using -Werror unconditionally it's better
to be safe than sorry.
Reported-by: Kevin Ushey <kevinushey@gmail.com>
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
According to POSIX and the Linux man page, select(2) is supposed to
report read ready if a file is at EOF. In the case of a FIFO, this
means that the pipe is empty and there are no writers. But there
seems to be an undocumented exception, observed on Linux and other
platforms: If no writer has ever been opened, then select(2) does not
report read ready. This can happen if a reader is opened with
O_NONBLOCK before any writers have opened.
This commit makes Cygwin consistent with those other platforms by
introducing a special EOF test, fhandler_fifo::select_hit_eof, which
returns false if there's never been a writer opened.
To implement this we use a new variable '_writer_opened' in the FIFO's
shared memory, which is set to 1 the first time a writer opens. New
methods writer_opened() and set_writer_opened() are used to test and
set this variable.
Addresses: https://cygwin.com/pipermail/cygwin/2022-September/252223.html
