Added mission type to MAVLink mission_count message

[hdino]

This pull request fixes the following bug:

While uploading the waypoints to the UAS, a mission_count message is sent. The struct mavlink_mission_count_t has a field mission_type, which was not set and therefore had a random value (so in most cases 0). You can find the possible values in MAVLink's common.h. I set it to MAV_MISSION_TYPE_MISSION.

Best,
Dino

[peterbarker]

Good find @hdino

This is a particularly troubling patch given the number of mavlink2 extensions that are now in use out there.

valgrind may find these, but adopting a pattern which reliably initialised the message on the stack would be a better approach.

[hdino]

@peterbarker Indeed! I guess the best way would be if the MAVLink C++ types had a constructor that takes values for all message fields as parameters. Then it's impossible to miss one (as long as the default constructor isn't used...).

[peterbarker]

On Thu, 14 May 2020, Dino Hüllmann wrote: @peterbarker Indeed! I guess the best way would be if the MAVLink C++ types had a constructor that takes values for all message fields as parameters. Then it's impossible to miss one (as long as the default constructor isn't used...).

Very few projects use the C++ bindings. I haven't checked - but these look like the C bindings to me. Peter

[hdino]

Yes, the C++ bindings are basically the same as the C bindings. I use them in my projects because then the MAVLink stuff doesn't flood the global namespace. However, they don't provide constructors other than the default one. So I suggest asking the pymavlink developers what they think about adding an additional value constructor.

Currently, some MAVLink types are initialized with memset(0), but 0 is probably not the value you want.

Do you have another idea, how the messages could be reliably initialised?

[Arne-W]

I just can repeat peter - good finding! Thanks for that!