Issue With VNAMELENMAX Constant in PDL::IO::HDF

[a-shahba]

I was trying to open an HDF4 file using PDL::IO::HDF::VS package. I observed that sometime that package failed to open the file (i.e. after calling new()) method and program aborted with the this message

corrupted size vs. prev_size
Abort (core dumped)

Recognizing that this is a memory issue, after some tests, I found out that this is related to VNAMELENMAX constant defined in PDL::IO::HDF package. Old versions of HDF4 library set a 64-character limit on lengths of some names, such as vgroup class names. However, this limitation has been lifted. For instance, starting HDF4 v4.2r5, vgroup class names are no longer limited to 64 characters.

[mohawk2]

Thanks for the report! Is there a recommended way in HDF4 to get the right size to use? And, similar to the HDF5 issue - feel like making a pull request? I'm busy fixing #498 right now.

[a-shahba]

No worries! I will work on a PR

[mohawk2]

Great! Let me know if you need any help. Please feel free to join the IRC channel (#pdl on irc.perl.org) also.

[mohawk2]

A thing I should have asked for when you initially reported this was for a test case. As it is, I'm guessing. Please always provide that in future.

[mohawk2]

There is no equivalent problem with VSsetname etc, which truncates names to VSNAMELENMAX (see https://github.com/HDFGroup/hdf4/blob/d7915df8eabb39879418d546d28362975345cb8c/hdf/src/vg.c#L480-L525).

I believe the above commit fixes the problem you identified. Please could you try the latest master and see if it works OK? If not, please provide data/code so I can reproduce it here.

[mohawk2]

Closing this. Please comment if there are problems.

[a-shahba]

@mohawk2 I tried to compile the master branch, but looks like I am missing some libraries. The unfortunate thing is that I cannot install anything on this machine. I have to ask the sys admin to do so. When the next PDL is released, I will ask the sys admin to install it and will test it out to see if the issue is truly fixed.

[mohawk2]

@a-shahba Please can you put here a cut-down test case so I can see on my machine if the problem is rectified?

If you say what libraries are missing locally I might be able to assist. I'm a bit surprised because I am expecting you ran the code that had problems, and the library requirements for HDF haven't changed in a long time?

[a-shahba]

@mohawk2 Sorry for the late reply. I could manage to compile and install the master branch and can confirm that your fix addressed the problem.