SIGHUP on pty closure

Marco atzeri marco.atzeri@gmail.com
Mon Jul 25 10:37:00 GMT 2011


On 7/21/2011 11:43 PM, Marco atzeri wrote:
> looking on the mc subshell issue, I found that mc
> suppose that the subshell will receive a SIGHUP
> when mc exit and close the master side of pty.
>
> Is such assumption wrong or it is a missing piece of
> cygwin pty implementation ?
>
>
>
> ------------- extract from subshell.c --------------
> /* Attach all our standard file descriptors to the pty */
>
> /* This is done just before the fork, because stderr must still */
> /* be connected to the real tty during the above error messages; */
> /* otherwise the user will never see them. */
>
> dup2 (subshell_pty_slave, STDIN_FILENO);
> dup2 (subshell_pty_slave, STDOUT_FILENO);
> dup2 (subshell_pty_slave, STDERR_FILENO);
>
> close (subshell_pipe[READ]);
> close (subshell_pty_slave); /* These may be FD_CLOEXEC, but just in
> case... */
> /* Close master side of pty. This is important; apart from */
> /* freeing up the descriptor for use in the subshell, it also */
> /* means that when MC exits, the subshell will get a SIGHUP and */
> /* exit too, because there will be no more descriptors pointing */
> /* at the master side of the pty and so it will disappear. */
> close (subshell_pty);
>
> /* Execute the subshell at last */
>
> switch (subshell_type)
> {
> case BASH:
> execl (shell, "bash", "-rcfile", init_file, (char *) NULL);
> break;
> ----------------------------------------------------------

It seems that mc is correct in the expectation.

http://pubs.opengroup.org/onlinepubs/9699919799/functions/close.html

"If fildes refers to the master side of a pseudo-terminal, and this is 
the last close, a SIGHUP signal shall be sent to the controlling 
process, if any, for which the slave side of the pseudo-terminal is the 
controlling terminal. It is unspecified whether closing the master side 
of the pseudo-terminal flushes all queued input and output."


I don't find such implementation on cygwin

fhandler_pty_master::close ()

Am I looking in the wrong place ?

Regards
Marco


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