Re: Bogus exit code 127 from a child process

[Takashi Yano <takashi.yano@nifty.ne.jp>]

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On Sun, 17 Mar 2024 21:03:58 +0900
Takashi Yano wrote:
> On Sun, 17 Mar 2024 19:21:16 +0900
> Takashi Yano wrote:
> > On Sun, 17 Mar 2024 13:03:40 +0300
> > Alexey Izbyshev wrote:
> > > On 2024-03-17 12:27, Takashi Yano wrote:
> > > > On Sun, 17 Mar 2024 12:01:55 +0300
> > > > Alexey Izbyshev wrote:
> > > >> On 2024-03-17 11:44, Takashi Yano wrote:
> > > >> > On Sun, 17 Mar 2024 11:14:16 +0300
> > > >> > Alexey Izbyshev wrote:
> > > >> >> Hello,
> > > >> >>
> > > >> >> I've been getting occasional "Error 127" from make -jN on seemingly
> > > >> >> random jobs. After reducing the set of jobs and eventually eliminating
> > > >> >> make, I've arrived to this one-liner:
> > > >> >>
> > > >> >> bash -c 'true & true & wait -n || echo 1: $? && wait -n || echo 2: $?'
> > > >> >>
> > > >> >> When run repeatedly, the second "wait -n" often reports 127.
> > > >> >>
> > > >> >> I've reproduced this in the following environments:
> > > >> >>
> > > >> >> * Cygwin 3.5.1, Windows 10 22H2 x64
> > > >> >> * Cygwin 3.4.6, Windows 10 22H2 x64 and Windows 7 x64
> > > >> >>
> > > >> >> I couldn't reproduce it in Cygwin 3.3.6 (WOW64) on Windows 7 x64.
> > > >> >
> > > >> > Could you please try latest cygwin 3.6.0 (TEST) ?
> > > >> 
> > > >> Tested with 3.6.0-0.82.gfc691d0246b9 on Windows 10 22H2 x64, the 
> > > >> problem
> > > >> still occurs.
> > > > 
> > > > In my evrironmen, trial for 1 hour does not reproduce the issue.
> > > > Could you please let us know your environment, i.e. CPU, amount of
> > > > memory, and so on?
> > > 
> > > It's been reproduced in a variety of environments:
> > > 
> > > * Windows 10 22H2 x64, Intel Core i7 11700, 32 GB RAM
> > > * Windows 10 22H2 x64, Intel Core i7 9700, 32 GB RAM
> > > * Windows 10 22H2 x64, Intel Core i7 6700, 32 GB RAM
> > > * Windows 7 SP1 x64, Intel Core i7 6700, 32 GB RAM
> > > 
> > > I'm surprised that you're not hitting it very quickly. The following 
> > > loop usually fails after a few iterations (rarely a hundred or so) in my 
> > > tests:
> > > 
> > > while bash -c 'true & true & wait -n || { echo 1: $?; exit 1; } && wait 
> > > -n || { echo 2: $?; exit 1; }'; do echo $((i++)); done
> > 
> > Thanks. My main PC still runs the above test for more than 15000 counts.
> > So, I tried another PC which CPU is Core i5 540M and could reproduce
> > the issue about 1 time per a few hundreds count.
> > 
> > I also tried to run sleep 0.1 instead of true, then, the issue happens
> > 1 time per a few decades counts.
> > 
> > I'll look into this problem. Thanks for the report.
> 
> In my environment, the issue is reproducible even with cygwin 3.3.6
> (32bit, i.e. WOW64) and bash 4.4.12(3)-release (i686-pc-cygwin).
> 
> What are the versions of bash in each systems?

And, the attached simple test case in C which does very similar things
with bash command could not reproduce the problem.

Can you reproduce the issue with attached STC?

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>

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#include <stdlib.h>
#include <unistd.h>
#include <sys/wait.h>
#include <stdio.h>

int main(int argc, char *argv[])
{
	int status;
	int num = 2;
	int cnt = 0;
	if (argc > 1) num = atoi(argv[1]);
	while (1) {
		for (int i=0; i<num; i++)
			if (fork() == 0) {
				execl("/usr/bin/sleep", "sleep", "0.1", NULL);
			}
		for (int i=0; i<num; i++) {
			waitpid(-1, &status, 0);
			if (WEXITSTATUS(status)) {
				printf("%d: %d\n", num, WEXITSTATUS(status));
				return 1;
			}
		}
	}
	return 0;
}