[Insight-developers] [Insight-users] 50 character limit in ITK on Win32?

[Mark Roden]

Hi Cory,

OK, I'll switch over to the developer's thread.

But it appears that the 50 character limit (or 51 character limit, as
reported by Alex Gouaillard) is only a problem with a particular
combination of vs2010 and cmake 2.8.3.  For those of us with vs2008,
it's just fine to have a 66 character (or longer) path.

I would propose, then, that this error message not be for any and all
versions of win32, but only for those compiler/cmake combinations
where this bug exists.  Otherwise, this limit is just overly
restrictive.

Thanks,
Mark

On Thu, May 3, 2012 at 2:24 PM, Cory Quammen <cquammen at cs.unc.edu> wrote:
> Mark,
>
> I think the path length choice was made conservatively because no one
> had the patience to figure out the exact length where things go wrong.
>
> The depth of the source tree, especially with the third-party
> libraries, is more of a problem that are the file name lengths in ITK.
>
> It might be more reasonable to issue a warning rather than halt with
> an error. You may want to propose this to the developers list to see
> what others think.
>
> - Cory
>
> On Thu, May 3, 2012 at 5:13 PM, Mark Roden <mmroden at gmail.com> wrote:
>> But a path length of 66 works.
>>
>> It appears that this patch was for a particular compiler (vs2010) and
>> a particular version of cmake (2.8.3).  That's a much more specific
>> issue than all win32 platforms; I'm on vs2008, and as I said, 66
>> characters works just fine.
>>
>> And I would be strongly in favor of making this a warning, rather than
>> hard limit, if it's difficult/impossible to detect that particular
>> combination of compiler/cmake versions.  I don't, and never have had,
>> an issue building in ITK in any random directory, regardless of path
>> length-- maybe because I tend to keep my path lengths lower than 100
>> characters.
>>
>> But if this does continue to be an issue, is there some kind of style
>> guide for path length?  I see some really absurdly long filenames in
>> there, and if it really is an issue with vs2010, then maybe that style
>> should be enforced (along with all of the other commit rules).
>>
>> On Thu, May 3, 2012 at 2:04 PM, Cory Quammen <cquammen at cs.unc.edu> wrote:
>>> Mark,
>>>
>>> The limit is there to save your sanity :-)
>>>
>>> Did you try to compile with a path length of 100 characters? When I
>>> did, I ran into a file-not-found complaint by the compiler when
>>> compiling GDCM. Then I checked to see that the file it is complaining
>>> about does indeed exist.
>>>
>>> See the long email thread that led to this restriction here:
>>>
>>> http://www.itk.org/pipermail/insight-developers/2011-June/019268.html
>>>
>>> Basically, the relative paths generated by CMake and limitations in
>>> the length of paths in Visual Studio lead to this limit.
>>>
>>> Cory
>>>
>>> On Thu, May 3, 2012 at 4:49 PM, Mark Roden <mmroden at gmail.com> wrote:
>>>> Hi all,
>>>>
>>>> I've just recompiled itk 4.0, and found that there's a 50 character
>>>> path limit for win32.
>>>>
>>>> What's the logic behind this?  I comment out that line, and everything
>>>> works perfectly fine.
>>>>
>>>> The filename limit for windows is 255 (260 including the drive letter
>>>> and trailing null), but each component of the path can be 255
>>>> characters long.  MacOS has the same limit for HFS+, where each
>>>> element is locked to 255, but the total path has to be 1024 or lower.
>>>> (source: http://en.wikipedia.org/wiki/Comparison_of_file_systems).  If
>>>> you're not using windows-specific programming, but just treating the
>>>> path as a string, there's a 255 character limit.
>>>>
>>>> With my base file path that's 66 characters long, the longest filename
>>>> I can find is 146:
>>>>
>>>> C:\Users\mmroden\Documents\src\MyProjectsinQT\ExternalLibs\itk\ITK\Documentation\Migration\ConstNeighborhoodIteratorGetBoundaryConditionChange.xml
>>>>
>>>> That's a far cry from 255.
>>>>
>>>> Just how deep are the paths in ITK anyway?  Is the directory tree
>>>> really 205 characters long?  Or is this just someone guessing without
>>>> actually checking?
>>>>
>>>> The problem with this is that I want to incorporate ITK building as
>>>> part of a build script, rather than having to checkin binary images
>>>> into a repo.  I'd have to add a portion to the script to remove the
>>>> limit.
>>>>
>>>> What if it were just set to 100?
>>>>
>>>> Thanks,
>>>> Mark
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>>>
>>>
>>>
>>> --
>>> Cory Quammen
>>> Research Associate
>>> Department of Computer Science
>>> The University of North Carolina at Chapel Hill
>
>
>
> --
> Cory Quammen
> Research Associate
> Department of Computer Science
> The University of North Carolina at Chapel Hill