[erlang-questions] has anyone else seen Erlang 19 break 'bash' after exit?

[Lukas Larsson]

Hello,

I think that it may be a change done in Erlang/OTP 18 that causes this
behaviour. Specifically OTP-12239. Using non-blocking I/O on stdin/stdout
seems to kind of work, until it doesn't. Different platforms and tools
handle it very differently.

The only "solution" that I can think of right now is to use dedicated read
and/or write threads within the VM to handle stdin/stdout, but I was hoping
to avoid having to do that.

The problem, for those that are interested, is that the O_NONBLOCK flag is
set on the file description, not the file descriptor. Which causes all
kinds of problems, I thought I had handled them all, but apparently not
enough.

Lukas

On Tue, Mar 14, 2017 at 1:35 PM, Igor Clark <igor.clark@REDACTED> wrote:

> Hello Matthias,
>
> Not sure if it's related, but I see bash v4.4.5 terminal I/O get really
> messed up on Mac OSX after the erlang runtime aborts. It happens whether
> through a NIF segfault during dev, or just by doing ^C and 'abort'. The
> terminal input becomes unusable, vim buffers don't display roughly half the
> text; 'reset' makes no difference, I have to close the Terminal.app window
> and start over. Haven't had time to dig into it at all, just kind of got
> used to it.
>
> I thought it might be R19, but I switched back to R18 and it still
> happened. Which made me wonder if it's anything to do with tmux, but I
> tried it in a standard Terminal window without tmux, and it happened then
> too. So I tried using the default OSX /bin/bash (which is v3.2.57) instead
> of the homebrew version (4.4.5) - and it didn't happen at all.
>
> Which is a long-winded way of saying, maybe this might also be a "recent
> bash" issue, rather than an erlang issue?
>
> Cheers,
> Igor
>
>
> On 13/03/2017 20:32, Matthias Lang wrote:
>
>> Hi,
>>
>> Erlang 19.1 and 19.2 seems to break something to do with terminal
>> input on some but not all of my Debian x86-64 machines. I took a quick
>> look through the recent mailing list archives and haven't seen any
>> mention of this. Maybe I missed it. Maybe it's just me.
>>
>> Example:
>>
>>     | ~ >uname -a
>>     | Linux hec 4.9.0-2-amd64 #1 SMP Debian 4.9.13-1 (2017-02-27) x86_64
>> GNU/Linux
>>     | ~ >read x
>>     | hello world
>>     | ~ >erl
>>     | Erlang/OTP 19 [erts-8.1] [source] [64-bit] [smp:4:4]
>> [async-threads:10] [hipe] [kernel-poll:false]
>>     |
>>     | Eshell V8.1  (abort with ^G)
>>     | 1>
>>     | BREAK: (a)bort (c)ontinue (p)roc info (i)nfo (l)oaded
>>     |        (v)ersion (k)ill (D)b-tables (d)istribution
>>     | a
>>     | ~ >read x
>>     | bash: read: read error: 0: Resource temporarily unavailable
>>
>> The "read error: 0: Resource temporarily unavailable" part is unexpected.
>> Using 'cat' instead of 'read' produces a similar error:
>>
>>     | cat: -: Resource temporarily unavailable
>>
>> 'strace' tells me something is screwy about stdin:
>>
>>     | read(0, 0x7f1010dbb000, 131072)         = -1 EAGAIN (Resource
>> temporarily unavailable)
>>
>> read(2) tells me EAGAIN suggests that stdin has been left in with
>> O_NONBLOCK.
>> Is that Erlang's problem to clean up, or is that supposed to happen on
>> program exit? I haven't read up on that.
>>
>> Doing the same thing on 17.4 works fine.
>>
>> Debian 3.16.39-1 and erts-8.2.1 produces a related by different
>> strangeness:
>>
>>     | 1>
>>     | BREAK: (a)bort (c)ontinue (p)roc info (i)nfo (l)oaded
>>     |       (v)ersion (k)ill (D)b-tables (d)istribution
>>     | a
>>     | $ sh: turning off NDELAY mode
>>
>> Can anyone else see this? Any idea what's up?
>>
>> Matt
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>
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