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robotology / idyntree

Multibody Dynamics Library designed for Free Floating Robots
BSD 3-Clause "New" or "Revised" License
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Strange behavior of YARPConversions templated functions #426

Open diegoferigo opened 6 years ago

diegoferigo commented 6 years ago

I'm facing a strange behavior in the YARPConversion helper function.

iDynTree has generic templates, such as:

https://github.com/robotology/idyntree/blob/d4a1cf98a80391937da6a040982c72764aec9a86/src/yarp/include/iDynTree/yarp/YARPConversions.h#L178-L185

and functions, which their presence should prevent the template to be instantiated. An example matching the template taken as an example is:

https://github.com/robotology/idyntree/blob/d4a1cf98a80391937da6a040982c72764aec9a86/src/yarp/include/iDynTree/yarp/YARPConversions.h#L113-L122

https://github.com/robotology/idyntree/blob/d4a1cf98a80391937da6a040982c72764aec9a86/src/yarp/src/YARPConversions.cpp#L109-L114

However, debugging some code which uses this function, I realized the regular function is never called. Instead, for some reason, the template is instantiated. This caused a problem because the difference between the two implementations is that the template fails when the two container do not have the same size (I was just reserving, not resizing the iDynTree::VecDynSize object).

Probably in this case, using template specialization would work smoother, but it is just a guess. I still don't get why the instantiation happens in the first place. Any idea? @traversaro

diegoferigo commented 6 years ago

Writing down the problem often helps solving the issue by yourself. After submitting this, I had the idea to check what function get instantiated, with this outcome:

bool iDynTree::toiDynTree<iDynTree::JointPosDoubleArray>(yarp::sig::Vector const&, iDynTree::JointPosDoubleArray&)

Despite class JointPosDoubleArray: public VectorDynSize, the template seems to have an higher priority regardless the inheritance.

If no one else has other comments, feel free to close this issue.

diegoferigo commented 5 years ago

Closing.

traversaro commented 5 years ago

This is indeed tricky and confusing for the users, but it should be easy to capture in a unit test. I did not remember reading this issue at the time it was opened. Ideally toiDynTree should work in the same way for VectorDynSize or any class that inherits publicly from it. Do you mind if we keep this issue open?

diegoferigo commented 5 years ago

Ideally toiDynTree should work in the same way for VectorDynSize or any class that inherits publicly from it

Definitely :+1: on this

Do you mind if we keep this issue open?

You're affecting my spring cleaning process :laughing: Not at all :)