New variance field for the Range message

[ejalaa12]

The Range message will get an additional field for the variance.
I don't know if this is relevant for you guys, but this issue is simply a notification, feel free to close it if it's not a change that you could benefit from.

You can see details about the PR here

[jlblancoc]

@ejalaa12 This has been finally addressed here:
67358e9

so MRPT >= v2.11.2 will use the new variance field.

[ejalaa12]

@jlblancoc awesome! I saw the commit, this a clever way of making sure the member exist.
I guess this makes it retro-compatibke with old version of the Range message as well.

[jlblancoc]

Exactly 👍

[jlblancoc]

However, for some reason, the if constexpr trick fails on Humble... hmm....

https://build.ros2.org/job/Hdev__mrpt2__ubuntu_jammy_amd64/349/console

03:46:44 [ 92%] Building CXX object libs/ros2bridge/CMakeFiles/ros2bridge.dir/src/range.cpp.o
03:46:44 /tmp/ws/src/mrpt2/libs/ros2bridge/src/range.cpp: In function ‘bool mrpt::ros2bridge::fromROS(const Range&, mrpt::obs::CObservationRange&)’:
03:46:44 /tmp/ws/src/mrpt2/libs/ros2bridge/src/range.cpp:43:78: error: ‘const Range’ {aka ‘const struct sensor_msgs::msg::Range_<std::allocator<void> >’} has no member named ‘variance’
03:46:44    43 |                 obj.sensedData.at(0).sensorNoiseStdDeviation = std::sqrt(msg.variance);
03:46:44       |                                                                              ^~~~~~~~

I'll investigate it.

[jolting]

This was added on March 15. It didn't make Humble.
ros2/common_interfaces@05d7e19

[jolting]

Maybe try it with declval?

template <class T>
struct has_variance<T, std::void_t<decltype(std::declval<T>().variance)>> : std::true_type
{
};

[jlblancoc]

This was added on March 15. It didn't make Humble. ros2/common_interfaces@05d7e19

Yeap, exactly! :-)

[jlblancoc]

@jolting It was something else... I just found (the hard way..) that everything inside an if constexpr() is actually parsed by the compiler (even if the condition is false)... except if it's inside a template. Solution -> move that part to a template, and it's now working (ignoring) on humble too! 4b6e108

PS: before that, I also tried the declval trick without luck... :-( Thanks!!