On 12/18/2019 2:32 PM, Corinna Vinschen wrote:
> On Dec 18 17:23, Marco Atzeri wrote:
>> Am 18.12.2019 um 15:42 schrieb Laurent R:
>>> Dear all,
>>>
>>> After the update to cygwin-3.1.1, mc (aka Midnight Commander) no longer
>>> starts. It goes into an infinite loop, if I go back to cygwin-3.0.7, mc
>>> works perfectly.
>>>
>>> I tested with cygwin-3.1.0, same problem.
>>>
>>> The MC version is 4.8.23 and the operating system is Windows 10 Pro x64
>>> 1903.
>>>
>>> Regards.
>>>
>>
>> confirmed
>>
>> there must be a race somewhere as running /usr/bin/mc.exe from strace
>> works fine.
>
> But that's not the only problem running mc AFAICS. I'm seeing an
> error message in the background:
>
> Cannot open named pipe /tmp/mc-corinna/mc.pipe.384
>
> /cygdrive/d/cyg_pub/devel/mc/mc-4.8.23-1.x86_64/src/mc-4.8.23/src/subshell/common.c:
> open: Permission denied
>
> It looks like there's another problem, this time with the new FIFO
> code.
>
> Ken, care to take a look?
I've just looked at the mc source code, and it seems that (under tcsh only), mc
creates a fifo and tries to open it twice as O_RDWR. This is not supported on
Cygwin, so the second attempt fails.
Here's the relevant code from src/subshell/common.c:
if (mc_global.shell->type == SHELL_TCSH)
{
g_snprintf (tcsh_fifo, sizeof (tcsh_fifo), "%s/mc.pipe.%d",
mc_tmpdir (), (int) getpid ());
if (mkfifo (tcsh_fifo, 0600) == -1)
[...]
/* Opening the FIFO as O_RDONLY or O_WRONLY causes deadlock */
if ((subshell_pipe[READ] = open (tcsh_fifo, O_RDWR)) == -1
|| (subshell_pipe[WRITE] = open (tcsh_fifo, O_RDWR)) == -1)
{
fprintf (stderr, _("Cannot open named pipe %s\n"), tcsh_fifo);
perror (__FILE__ ": open");
mc_global.tty.use_subshell = FALSE;
[...]
Under bash, zsh, and some other shells, mc uses ordinary pipes rather than
FIFOs. I have no idea why tcsh is treated differently.
Until someone[*] gets around to making it possible to open a FIFO twice for
reading, I don't think there's anything we can do about it. I also don't know
how important this is for mc. I don't use tcsh or mc, so I can't judge.
Ken
[*] I will probably look into this at some point if there's enough demand for
it, but I'd like the new FIFO code to get lots of testing first.
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