[Hdf-forum] Multiple file opens

[Elena Pourmal]

Allen,

You said that your program failed. Did it print out errors from the HDF5 library? This what we would like to see to assess the problem (a bug or a feature ;-)
Having source code of the failing program would be even more helpful. 

Thank you!

Elena
On Jan 14, 2010, at 3:39 PM, Allen Sanderson wrote:

> Hello Elena,
> 
> Not a problem to send the stack info. Rarely do I gather this info so could you point me to some sample code that will give you the info you need.
> 
> Cheers,
> 
> Allen
> 
> 
> Allen Sanderson
> SCI Institute
> University of Utah
> www.sci.utah.edu
> 
> 
> 
> On Jan 14, 2010, at 1:13 PM, Elena Pourmal wrote:
> 
>> Allen,
>> 
>> Thank you for your report!
>> On Jan 14, 2010, at 12:37 PM, Allen Sanderson wrote:
>> 
>>> HI,
>>> 
>>> This morning I was able to track down a bug with a file with external links where the file was opened twice simultaneously. The first open was read only. The second open was read write.  However, if I create the file with the exact same hierarchy but without links I do not see the bug. I found this odd.
>>> 
>>> Here is the sequence
>>> 
>>> fp1 = open file read only
>>> 
>>> gp1 = open /group using fp1 (note /group is an eternal link)
>>> 
>>> fp2 = open file read/write
>>> 
>>> dp2 = open /group/dataset using fp2
>>> 
>>> the last open fails. I can understand the failure given the gp1 is read only and dp2 which is under it is trying to perhaps do a write which could cause some problems.  So it fails.
>>> 
>>> However, if the file has the same hierarchy but without the link it does not fail. I found this behavior strange as I would have expected both to behave the same.
>>> 
>>> Obviously, one solution is not to open the file twice which is certainly possible but also having both opens be read/write also works. But I am more concerned with the inconsistency. 
>>> 
>> yes, good point. Could you please send us an error stack from the failed program? 
>> 
>> In our defense :-) RM entry for H5Fopen states "A file can often be opened with a new H5Fopen call without closing an already-open identifier established in a previous H5Fopen or H5Fcreate call. Each such H5Fopen call will return a unique identifier and the file can be accessed through any of these identifiers as long as the identifier remains valid. In such multiply-opened cases, all the open calls should use the same flags argument."
>> 
>> Elena
>> 
>>> 
>>> Cheers,
>>> 
>>> Allen
>>> 
>>> 
>>> Allen Sanderson
>>> SCI Institute
>>> University of Utah
>>> www.sci.utah.edu
>>> 
>>> 
>>> 
>>> _______________________________________________
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>>> Hdf-forum at hdfgroup.org
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>> 
>> _______________________________________________
>> Hdf-forum is for HDF software users discussion.
>> Hdf-forum at hdfgroup.org
>> http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
> 
> _______________________________________________
> Hdf-forum is for HDF software users discussion.
> Hdf-forum at hdfgroup.org
> http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org

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