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Avoid segfault and improve error warnings #603

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Avoid segfault and improve error warnings #603

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a9c983d
Avoid segfault and improve error warnings
sjahr Aug 12, 2024
4bac6ac
Fix formatting
sjahr Aug 12, 2024
fe953d0
Remove duplicate print statement
sjahr Aug 12, 2024
3d3d1b7
Revert unnecessary changes
sjahr Aug 12, 2024
08eaab1
Revert logging change & change log level
sjahr Aug 12, 2024
331652f
Formatting
sjahr Aug 12, 2024
7ba59e8
Change log level
sjahr Aug 12, 2024
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1 change: 1 addition & 0 deletions core/src/container.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -345,6 +345,7 @@ Stage* ContainerBase::findChild(const std::string& name) const {
else if (auto* parent = dynamic_cast<const ContainerBase*>(child.get()))
return parent->findChild(name.substr(pos + 1));
}
RCLCPP_DEBUG_STREAM(rclcpp::get_logger("ContainerBase"), fmt::format("Child '{}' not found", name));
return nullptr;
}

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5 changes: 5 additions & 0 deletions core/src/stages/compute_ik.cpp
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Expand Up @@ -314,6 +314,11 @@ void ComputeIK::compute() {

link = scene->getCurrentState().getRigidlyConnectedParentLinkModel(ik_pose_msg.header.frame_id);

if (!link) {
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knowsFrameTransform(), a few lines above, should have validated that the frame exists.
Under what circumstances do you run into a segfault here?
I cannot imagine a valid frame that returns NULL here.

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There seem to be cases under which getRigidlyConnectedParentLinkModel returns a nullptr. Are they all covered by knowsFrameTransform?

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Not sure if I am understanding it correctly. I tried to add comments to the code to make it more comprehensible in https://github.com/moveit/moveit2/pull/2969/files. Do you think they are accurate? My current understanding is that this function returns a nullptr when there is nothing connected to the parent or when the transform between the parent body and the given frame is unknown.

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@rhaschke rhaschke Aug 12, 2024 •
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There seem to be cases under which getRigidlyConnectedParentLinkModel returns a nullptr. Are they all covered by knowsFrameTransform?

Yes, they should be covered by knowsFrameTransform. If not, that's probably a bug. Please state your concrete problem.

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My current understanding is that this function returns a nullptr when there is nothing connected to the parent or when the transform between the parent body and the given frame is unknown.

IMO, this function should return NULL only if the given frame is unknown. Note that this function finds the parent link, which frame is connected to.

RCLCPP_WARN_STREAM(
LOGGER, fmt::format("ik frame '{}' is not rigidly connected to any link", ik_pose_msg.header.frame_id));
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The error message doesn't make sense: an existing frame needs to be connected to some link.

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Would this be more precise?

Suggested change
LOGGER, fmt::format("ik frame '{}' is not rigidly connected to any link", ik_pose_msg.header.frame_id));
LOGGER, fmt::format("ik frame '{}' is not connected to any parent link", ik_pose_msg.header.frame_id));

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As I said, I expect this to return NULL if and only if frame doesn't exist. Do you have other evidence?

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@sjahr: I'm still curious to learn about your concrete issue.
In which case does getRigidlyConnectedParentLinkModel returns NULL, which is not handled before by knowsFrameTransform?

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Sorry, I cannot share more info on this at the moment 😞 I'll try debugging it further and hopefully figure out what the real source behind this is.

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I'm not expecting a detailed error analysis, but ideally a code snippet reproducing your segfault - I assume you observed a segfault in some code.

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@sjahr sjahr Aug 20, 2024 •
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Yes, unfortunately I don't have access to the code that causes the error and it seems to happen only in a HW setup. If you'd prefer that I can close this PR for now and come back later with more solid changes.

return;
}
// transform target pose such that ik frame will reach there if link does
target_pose = target_pose * ik_pose.inverse() * scene->getCurrentState().getFrameTransform(link->getName());
}
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