[ros-users] Rosmake depends problem with flann

[Brian Gerkey]

On Thu, Nov 4, 2010 at 12:41 PM, Cedric Pradalier
<cedric.pradalier at mavt.ethz.ch> wrote:
> In addition to solving the opencv issue, would it make sense for
> rosmake, rosdep or rospack to complain if a library appears two times in
> the exports of 2 different manifests?

hi Cedric,

That might be tricky to do properly.  What happens when two packages
that use X export -lX11?  It's correct for each of them export that
lib, because it's needed to link against code in each package.

You really want to catch the case where two packages export -lfoo,
where libfoo was built *inside* each package.  But we don't presently
have a way in the manifest library exports to distinguish between libs
that are built by the package, and those that are not.

	brian.

>
> On 11/04/10 12:35, Brian Gerkey wrote:
>> hi Garratt,
>>
>> Package dependencies in the manifest are not meant to be ordered, and
>> you shouldn't rely on ordering to produce a particular behavior.  In
>> this case, as Radu says, the problem is that the ROS packages opencv2
>> and flann conflict with each other.  That conflict should be resolved.
>>
>>       brian.
>>
>> On Thu, Nov 4, 2010 at 11:36 AM, Radu Bogdan Rusu<rusu at willowgarage.com>  wrote:
>>
>>> Garratt,
>>>
>>> This is a nasty problem, and we should fix the way FLANN is exposed from within OpenCV (I would argue that it shouldn't
>>> really be exposed from within OpenCV in ROS, as long as we have a ROS package for FLANN). In general, this practice of
>>> just "eating up libraries" -- that is, include a library (FLANN) into another library (OpenCV) should be avoided for
>>> many reasons. As long as FLANN remains standalone, it should be included as a dependency through the normal
>>> rosdep/depend mechanisms.
>>>
>>> The OpenCV case is a bit different though, because OpenCV itself is not a ROS package but an external "3rd party
>>> dependency", wrapped in a ROS meta-package (opencv2). That means that it was easier for OpenCV to just copy FLANN inside
>>> it rather than using some CMake/Makefile logic to search for it on the system. The latter is even more complicated as we
>>> wouldn't really install FLANN on our systems globally, but use a ROS meta-package for it, so OpenCV would need to be
>>> able to search through other ROS meta-packages...
>>>
>>>
>>> Cheers,
>>> Radu.
>>>
>>>
>>> On 11/03/2010 10:44 PM, garratt wrote:
>>>
>>>> Hi all,
>>>>
>>>> I'm using the flann library in PCL.  I recently came across a rather
>>>> annoying phenomenon:  opencv also includes a version of flann that is
>>>> similar enough to not generate compile errors, but causes segfaults when
>>>> I run code compiled with it.  When tracking down how I started using the
>>>> wrong flann, I realized that the cmake voodoo that is rosmake seems to
>>>> include a library by it's _last_ mention, rather than the first:
>>>>
>>>> in my manifest file:
>>>>
>>>> <depend package="pcl"/>
>>>> <depend package="depends_on_opencv"/>
>>>> <depend package="pcl"/>
>>>>
>>>> fails, whereas:
>>>>
>>>> <depend package="pcl"/>
>>>> <depend package="pcl"/>
>>>> <depend package="depends_on_opencv"/>
>>>>
>>>> does not.
>>>>
>>>> I could solve this problem in my case, because I owned all the manifest
>>>> files.  However, I can image a scenario where I need to include a
>>>> package that, through the dependency ordering causes my package to
>>>> include the wrong library.
>>>>
>>>> Is my perception of the rosmake dependency inclusion process correct? If
>>>> so, maybe changing to a 'first inclusion' paradigm might be appropriate.
>>>>
>>>> thanks,
>>>> Garratt
>>>>
>>>>
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>>>>
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>
> --
> Dr. Cedric Pradalier
> http://www.asl.ethz.ch/people/cedricp
>
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