Re: [Quilt-dev] Race in test suite (faildiff.test)

[Andreas Grünbacher]

2018-01-25 13:43 GMT+01:00 Jean Delvare <address@hidden>:
> Hi Andreas,
>
> Once in a while, the quilt test suite fails with:
>
> [faildiff.test]
> [1] $ mkdir patches -- ok
> [3] $ quilt new test.diff -- ok
> [6] $ cat > test.txt -- ok
> [8] $ quilt add test.txt -- ok
> [13] $ chmod -r test.txt -- ok
> [15] $ quilt refresh -- ok
> [18] $ echo 1 -- ok
> [21] $ chmod +r test.txt -- ok
> [25] $ printf "\\002\\000\\001" > test.bin -- ok
> [26] $ quilt add test.bin -- ok
> [29] $ printf "\\003\\000\\001" > test.bin -- ok
> [30] $ quilt diff -pab --no-index -- failed
> Diff failed on file 'test.bin', aborting !~ (Files|Binary files) a/test\.bin 
> and b/test\.bin differ
> Binary files a/test.bin and b/test.bin differ != Diff failed on file 
> 'test.bin', aborting
> [33] $ echo 1 -- ok
> [36] $ quilt refresh -- ok
> [38] $ echo 1 -- ok
> 15 commands (14 passed, 1 failed)
> Makefile:410: recipe for target 'test/.faildiff.ok' failed
> make: *** [test/.faildiff.ok] Error 1
>
> The reason is that the 2 messages are not printed in the same order as
> expected. Looking at the code, I can't explain how this can possibly
> happen. "Binary files ..." is printed first in the code, and the
> subprocess which prints it is already gone by the time we reach the
> line which prints "Diff failed ...". It has to be, because we check its
> status code before printing "Diff failed ...".
>
> The inversion is very rare, the test can succeed hundred or even
> thousand times before if fails again. I'm using the following command
> to reproduce the error:
>
> $ n=0 ; while make check-faildiff ; do let n=n+1 ; echo $n ; rm 
> test/.faildiff.ok ; done
>
> Do you have any idea how this can happen? Am I missing something, or
> could this be a bug in bash? I tried a few tricks (stdbuf, wait...) but
> nothing seems to solve the problem. If you (or anyone reading this)
> have any suggestion, that would be very welcome.

The command "quilt diff -pab --no-index" writes to stdout as well as
stderr, so it's undefined which of the two lines the run script will
see first. Try appending a "2>&1" to direct all output to a single
file.

Andreas