Type mismatch in Blackboard::set() function

[ozgudum]

I am getting this error when I try to set navigation goal in ROS2 navigation2 stack:

Action server failed while executing action callback: "Blackboard::set() failed: once declared, the type of a port shall not change. Declared type [geometry_msgs::msg::PoseStamped_<std::_1::allocator >] != current type [geometry_msgs::msg::PoseStamped<std::__1::allocator >]"

It was weird because it's complaining about port type mismatch but demangled types seems to be identical. Then, I traced the error and it seems to occur in the line below in set() function in blackboard.h

if( locked_type && locked_type != &typeid(T) && locked_type != &temp.type() )

I found out that both returned types are same as locked_type:

demangle(locked_type) -> geometry_msgs::msg::PoseStamped_<std::_1::allocator >
demangle(typeid(T)) -> geometry_msgs::msg::PoseStamped<std::_1::allocator >
demangle(temp.type()) -> geometry_msgs::msg::PoseStamped<std::__1::allocator >

but pointers to types are different:

locked_type -> 0x101489060
&typeid(T) -> 0x120fdc3a0
&temp.type()-> 0x120fdc3a0

Interestingly, address mismatch doesn't occur for all types. I wonder why comparison of type addresses was preferred over comparison of type values directly?

If I change the line as below to compare type values directly, I no longer get type mismatch error.

if( locked_type && *locked_type != typeid(T) && *locked_type != temp.type() )

If this change makes sense, I can create a pull request for this fix.

[facontidavide]

I should look into this. Thanks for reporting

[facontidavide]

fix added. thanks!

[SteveMacenski]

@facontidavide you mentioned you fixed this, could this ticket be closed?

[alsora]

Hi, it looks like that I have a very similar problem.
I'm using BehaviorTree.cpp 3.7.0
Interestingly, this only happens when subtrees are involved.

See this example XML.

    <BehaviorTree ID="TestTree">
        <Control ID="Sequence">
            <Action ID="DriveToPose" in_goal="{to_pose}"/>
        </Control ID="Sequence">
    </BehaviorTree>

    <BehaviorTree ID="Main">
        <Control ID="Sequence">
            <Action ID="GetPose" out_pose="{pose}"/>
            <Action ID="DriveToPose" in_goal="{pose}"/>
        </Control ID="Sequence">
    </BehaviorTree>

    <BehaviorTree ID="MainWithSubtree">
        <Control ID="Sequence">
            <Action ID="GetPose" out_pose="{pose}"/>
            <SubTree ID="TestTree" to_pose="pose"/>
        </Control ID="Sequence">
    </BehaviorTree>

All variables are of type geometry_msgs::msg::PoseStamped.
The trees Main and MainWithSubtree are supposed to be equivalent.
However, although Main works fine, MainWithSubtree produces the error mentioned in the first post.

The same problem also happens if I use a SubTreePlus node.

[facontidavide]

I will investigate.

[alsora]

@facontidavide FYI, I think I found why this happens in my code.
I'm using a custom routine to load plugins rather than calling registerFromPlugin() method.

• If I use this (which is equivalent to what registerFromPlugin() does) IT WORKS

    BT::SharedLibrary loader;
    loader.load(library_name);
    using register_func_t = void (*)(BT::BehaviorTreeFactory&);
    auto func = reinterpret_cast<register_func_t>(loader.getSymbol(BT::PLUGIN_SYMBOL));
    func(factory);

• If I use this version IT DOES NOT WORK

    auto library = std::make_shared<rcpputils::SharedLibrary>(library_name);
    using register_func_t = void (*)(BT::BehaviorTreeFactory&);
    auto func = reinterpret_cast<register_func_t>(library->get_symbol(BT::PLUGIN_SYMBOL));
    func(factory);

Note how in one case I use the BT::SharedLibrary class, while in the other I'm using the ROS 2 rcpputils::SharedLibrary class.
I have no idea why this happens, but from the tests I did so far, doing this change seems to fix the problem.

[facontidavide]

no idea.

[alsora]

Thanks to @matt-cross, we think that we know what causes the problem.
Citing his words:
the commit 4428f00 fixed one of the two comparisons between port types present in the codebase.
There's another instance that still compares using addresses: https://github.com/BehaviorTree/BehaviorTree.CPP/blob/3.7.0/src/blackboard.cpp#L25

The reason why it works with the BT::SharedLibrary but not with the rcpputils::SharedLibrary is because the former uses the RTLD_GLOBAL flag https://github.com/BehaviorTree/BehaviorTree.CPP/blob/3.7.0/src/shared_library_UNIX.cpp#L23 which appears to solve the issue in some situations (like the one I posted above).

Is there a reason why the fix mentioned above was not applied to all types comparisons?
This should be the correct approach, regardless of the flags used to load the library.

[facontidavide]

branch v3.8 fixed (master should be ok) ! @alsora thanks for finding the solution and sorry if it took me so long to come back to you.