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Re: wait4(2) do not fail with WNOHANG if there is no child

On 06.11.2016 11:53, Kamil Rytarowski wrote:
> On 06.11.2016 11:42, Robert Elz wrote:
>>     Date:        Sun, 6 Nov 2016 10:39:22 +0100
>>     From:        Nicolas Joly <>
>>     Message-ID:  <>
>>   | Just tested it on 7.0.2 NetBSD/amd64 under qemu, and it works as
>>   | expected. Looks like a -current regression.
>> In -current, the primary wait*() interface is wait6() - which is
>> posix waitid() (also available) plus the extra args needed to allow
>> it to also implement wait() wait3() waitpid() and wait4().
>> Posix is less clear on whether waitid() is supposed to return 0 or
>> ECHILD when WNOHANG is set, and there are no (applicable) children
>> (none that match the pid/flags specified - which includes no children
>> at all of course.)
>> 	If WNOHANG was specified and status is not available for any
>> 	process specified by idtype and id, 0 shall be returned.
>> but also ...
>> 	[ECHILD]
>>   	  The calling process has no existing unwaited-for child processes.
>> but generally, the error values only apply when the sys call is stated
>> to return an error, which waitid() does not specify when WNOHANG is
>> set (unlike it does for waitpid()).
>> We haven't yet switched to implementing wait4() (and the other older calls
>> all of which use the wait4() interface) via wait6(), so the question now
>> is, does this get changed just for the wait4() interface, or for wait6()
>> (and hence waitid()) as well.
>> kre
> I will extend our ATF tests to validate it.
> In general the new behavior seems to be working as intended and is
> reproducible on other major OSes.

I was wrong, it works without triggered assert(3) on Linux, I will try
to investigate it.

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