| namespace Eigen { |
| |
| /** \eigenManualPage TopicPassingByValue Passing Eigen objects by value to functions |
| |
| Passing objects by value is almost always a very bad idea in C++, as this means useless copies, and one should pass them by reference instead. |
| |
| With %Eigen, this is even more important: passing \ref TopicFixedSizeVectorizable "fixed-size vectorizable Eigen objects" by value is not only inefficient, it can be illegal or make your program crash! And the reason is that these %Eigen objects have alignment modifiers that aren't respected when they are passed by value. |
| |
| For example, a function like this, where \c v is passed by value: |
| |
| \code |
| void my_function(Eigen::Vector2d v); |
| \endcode |
| |
| needs to be rewritten as follows, passing \c v by const reference: |
| |
| \code |
| void my_function(const Eigen::Vector2d& v); |
| \endcode |
| |
| Likewise if you have a class having an %Eigen object as member: |
| |
| \code |
| struct Foo |
| { |
| Eigen::Vector2d v; |
| }; |
| void my_function(Foo v); |
| \endcode |
| |
| This function also needs to be rewritten like this: |
| \code |
| void my_function(const Foo& v); |
| \endcode |
| |
| Note that on the other hand, there is no problem with functions that return objects by value. |
| |
| */ |
| |
| } |
