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

[enh]

On Mon, Apr 27, 2015 at 12:30 PM, Isaac Dunham <ibid.ag at gmail.com> wrote:
> On Mon, Apr 27, 2015 at 08:36:53AM -0700, enh wrote:
>> On Sun, Apr 26, 2015 at 7:30 PM, Rich Felker <dalias at libc.org> wrote:
>> > On Sat, Apr 25, 2015 at 12:14:44PM -0700, enh wrote:
>> >> what's the plan wrt SIGPIPE? the desktop is pretty inconsistent. many
>> >> (but not all) commands install a signal handler that does _exit(0).
>> >> others (coreutils 8.21's ls, say) do nothing. normally "what you do
>> >> about SIGPIPE" isn't a problem but on Android that leads to a crash
>> >> report and people filing "ls crashed" bugs against me. (our default
>> >> shell PS setup is also noisy about crashes.)
>> >
>> > Why not just *block* SIGPIPE (with sigprocmask) so that the write
>> > returns an error (EPIPE) and the program applies the same logic it
>> > would for any other write error?
>>
>> toybox does a little better than toolbox there thanks to xwrite, but
>> i've yet never met anyone who checks the return value of printf...
>
> vmstat.c, cal.c, and see xprintf().
> In some places the choice of non-erroring functions is deliberate, so
> that a failure to write will not lead to an early exit.
>
>> plus there's the question of whether giving up because you're writing
>> to a broken pipe is an error exit or not. you could add a special case
>> to xwrite (and add xprintf and xputs and...), but since the whole idea
>> is that code shouldn't have to care, it's easier just to install a
>> signal handler that does _exit(0).
>
> There are xputs and xprintf already.
>
> Calling _exit() is wrong for toybox, since you cannot use atexit()
> type code (eg, delete tempfiles on exit) - xexit() is the recommended
> path for toybox.
> Using a fixed return value is wrong; for an example, grep returns
> 0 for "line matched", 1 for "no match", and >1 for errors.

(GNU grep 2.16 thinks grep should just die with SIGPIPE.)

-- 
Elliott Hughes - http://who/enh - http://jessies.org/~enh/
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