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From Martin Sebor <se...@roguewave.com>
Subject Re: infinite loop in exec
Date Fri, 25 May 2007 00:40:36 GMT
I've looked into this problem some more and discovered that
the test actually does generate that much data due to what
looks like a bug in glibc. I've opened a bug report with
Red Hat and created an issue to track it on our end. See
https://issues.apache.org/jira/browse/STDCXX-428. I also
linked it to the infinite loop issue that Mark so speedily
opened yesterday:
https://issues.apache.org/jira/browse/STDCXX-426

Now that I know what the problem is I should be able to fix
the test so as to avoid this misbehavior.

That said, I think the problem illustrates that we should
also make exec more robust and less prone to getting into
trouble because of misbehaved tests. Maybe we should put
a cap on the amount of data tests are allowed to generate
before getting cut off? In addition, instead of reading
the test output one character at a time, exec should read
it line by line or in bigger chunks. I'll leave it to Andrew
to investigate which approach makes the most sense :)

Martin

Martin Sebor wrote:
> Andrew Black wrote:
>> Probably wouldn't hurt to open a jira for this, as I'm currently 
>> running a sweep of results for our other products, and this may take a 
>> little time to look into.
> 
> Wow, looks like it's already done! (Thanks Mark!)
> 
>>
>> Interestingly, 
>> http://people.apache.org/~sebor/stdcxx/results/redhat_as-4.0-amd64-gcc-64b-3.4.6-12d-cfg-l.gz.txt

>> indicates that the trunk version of the 21.cwchar test produces the 
>> following message when run under the exec utility:
>>> NAME                      STATUS WARN ASSERTS FAILED PERCNT    
>>> USER     SYS    REAL
>>> 21.cwchar                      0    0     169     10    94%   0.000   
>>> 0.000   0.020
> 
> Yeah, I've seen that too.
> 
>>
>> However, if your working copy has changed as a result of work you've 
>> been doing, this data is likely not relevant.
> 
> That's a good point. I have reproduced the same behavior with
> a fresh sync to the head of trunk.
> 
> Martin
> 
>>
>> --Andrew Black
>>
>> Martin Sebor wrote:
>>> I'm running into an (almost?) infinite loop when running some
>>> of our tests under the exec utility on Linux (in a 12D build
>>> with gcc 3.4.6 on Red Hat Advanced Server 4, I haven't tried
>>> other configurations). The initial output of strace for one
>>> of the tests, 21.cwchar, is in the attached file. The test
>>> by itself runs fine to completion and doesn't produce any
>>> unusual output (no NULs).
>>>
>>> Andrew, when you have a chance, can you take a look at it?
>>> If that's not going to be soon let me know if I should open
>>> an issue.
>>>
>>> Martin
> 


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