[Toybox] default SIGPIPE handler that calls _exit(0)?

[enh]

On Thu, Feb 16, 2017 at 1:46 PM, Rob Landley <rob at landley.net> wrote:
> On 02/15/2017 06:43 PM, enh wrote:
>> works for me, thanks. the comment isn't quite right though. patch attached.
> ...
>> -  // Bionic's dynamic linker adds a handler to report SIGPIPE as an error,
>> -  // then doesn't want that behavior for toybox. So disable it for bionic.
>> +  // Up to and including Android 6.0 (Marshmallow), bionic's dynamic linker
>> +  // added a handler to cause a crash dump on SIGPIPE. That was removed in
>> +  // Android 7.0 (Nougat), but Android still gets bug reports about the
>> +  // regular "ps: write: broken pipe" output when someone pipes the output
>> +  // of ps into head.
>>    if (CFG_TOYBOX_ON_ANDROID) signal(SIGPIPE, SIG_DFL);
>
> The new code sets it to SIG_DFL, and you said that works for you, so
> where is the "regular" error message you referred to coming from?

an excellent question, with a non-obvious answer...

it turns out that adbd sets SIGPIPE to SIG_IGN, and that's propagated
to the shell and hence to toybox. so command-line stuff on Android
sees a lot more EPIPEs than you'd expect. seems unintentional, so i'll
try to find time to fix that tomorrow.

> Built against glibc:
>
> $ ./ps -A | head
>   PID TTY          TIME CMD
>     1 ?        00:01:01 init
>     2 ?        00:00:01 kthreadd
>     3 ?        00:16:17 ksoftirqd/0
>     5 ?        00:00:00 kworker/0:0H
>     7 ?        05:17:42 rcu_sched
>     8 ?        00:00:00 rcu_bh
>     9 ?        00:00:44 migration/0
>    10 ?        00:00:43 watchdog/0
>    11 ?        00:00:27 watchdog/1
> landley at driftwood:~/toybox/toy3$
>
> Built against musl:
>
> $ ./ps -A | head
>   PID TTY          TIME CMD
>     1 ?        00:01:01 init
>     2 ?        00:00:01 kthreadd
>     3 ?        00:16:17 ksoftirqd/0
>     5 ?        00:00:00 kworker/0:0H
>     7 ?        05:17:47 rcu_sched
>     8 ?        00:00:00 rcu_bh
>     9 ?        00:00:44 migration/0
>    10 ?        00:00:43 watchdog/0
>    11 ?        00:00:27 watchdog/1
> landley at driftwood:~/toybox/toy3$
>
> I'm not seeing this error message here?
>
> Rob
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-- 
Elliott Hughes - http://who/enh - http://jessies.org/~enh/
Android native code/tools questions? Mail me/drop by/add me as a reviewer.