[eigen] About alignement: two use cases

[<hamelin.philippe@xxxxxxx>]

Hello,

 

I have some use cases that I'm not sure if they respect the alignement contraints. I would be glad to to have your opinion about that.

 

USE CASE #1

===========================

 

Let say I have a class looking like this:

 

class A

{

public:

 

    Eigen::Vector6d v;

 

    EIGEN_MAKE_ALIGNED_OPERATOR_NEW

};

 

So far, I think this is the right way to do it. However, if another class derive from it:

 

class B : public A

{

    ....

}

 

Does the class B has also to use the EIGEN_MAMKE_ALIGNED_OPERATOR_NEW macro?

 

USE CASE #2

===========================

 

Let say I have a static library compiled with the EIGEN_DONT_ALIGN flash, which contains this class:

 

class C

{

public:

 

    Eigen::Vector6d v;

} 

 

Then, if I use this class from another program that is NOT compiled with EIGEN_DONT_ALIGN, e.g.:

 

int main(void)

{

    C* my_C = new C();

 

    Eigen::Vector6d my_v = my_C.v;

 

    return 0;

}

 

In that case, the "v" member of class C is implicitly not aligned. However, the progam doesn't specify anything about alignement. Does this makes sense? Does the casting will be done correctly as in:

 

Eigen::MAtrix<double, 6, 1, Eigen::DontAlign> v_unaligned;

Eigen::MAtrix<double, 6, 1> v_aligned;

 

v_aligned = v_unaligned;

 

 

Thank you,

 

------------------------------------
Philippe Hamelin, ing. jr, M. Ing
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