Fix segfault in Bullet Featherstone plugin when loading ball joint#868
Merged
Conversation
Signed-off-by: momo <2438833481@qq.com>
There was a problem hiding this comment.
Pull request overview
Fixes a crash in the Bullet Featherstone SDF model construction path when encountering joints without an axis definition (notably ball joints), improving robustness while loading SDF models.
Changes:
- Added a null check around
joint->Axis()before reading axis-dependent limits / damping / effort parameters. - Prevented axis-derived joint metadata from being populated when the axis is absent.
Comments suppressed due to low confidence (1)
bullet-featherstone/src/SDFFeatures.cc:862
- The new null check guards the property assignments, but
joint->Axis()is still dereferenced unconditionally when creatingbtMultiBodyJointLimitConstraint. IfAxis()can be nullptr for any non-ball joint (e.g., malformed SDF), this will still segfault. Consider cachingaxis = joint->Axis()once and only creating the limit constraint whenaxisis non-null (otherwise skip and emit an error/warning).
if (::sdf::JointType::BALL != joint->Type())
{
jointInfo->jointLimits =
std::make_shared<btMultiBodyJointLimitConstraint>(
model->body.get(), i,
static_cast<btScalar>(joint->Axis()->Lower()),
static_cast<btScalar>(joint->Axis()->Upper()));
world->world->addMultiBodyConstraint(jointInfo->jointLimits.get());
💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.
Comment on lines
+831
to
+852
| if (joint->Axis()) | ||
| { | ||
| model->body->getLink(i).m_jointLowerLimit = | ||
| static_cast<btScalar>(joint->Axis()->Lower()); | ||
| model->body->getLink(i).m_jointUpperLimit = | ||
| static_cast<btScalar>(joint->Axis()->Upper()); | ||
| model->body->getLink(i).m_jointFriction = | ||
| static_cast<btScalar>(joint->Axis()->Friction()); | ||
| model->body->getLink(i).m_jointMaxVelocity = | ||
| static_cast<btScalar>(joint->Axis()->MaxVelocity()); | ||
| model->body->getLink(i).m_jointMaxForce = | ||
| static_cast<btScalar>(joint->Axis()->Effort()); | ||
|
|
||
| jointInfo->minEffort = -joint->Axis()->Effort(); | ||
| jointInfo->maxEffort = joint->Axis()->Effort(); | ||
| jointInfo->minVelocity = -joint->Axis()->MaxVelocity(); | ||
| jointInfo->maxVelocity = joint->Axis()->MaxVelocity(); | ||
| jointInfo->axisLower = joint->Axis()->Lower(); | ||
| jointInfo->axisUpper = joint->Axis()->Upper(); | ||
| jointInfo->damping = joint->Axis()->Damping(); | ||
| jointInfo->springStiffness = joint->Axis()->SpringStiffness(); | ||
| jointInfo->springReference = joint->Axis()->SpringReference(); |
There was a problem hiding this comment.
Within the if (joint->Axis()) block, joint->Axis() is called repeatedly. Caching the pointer/reference once (e.g., const auto *axis = joint->Axis();) will make the code clearer and avoids repeated virtual calls / pointer chasing.
| @@ -828,26 +828,29 @@ Identity SDFFeatures::ConstructSdfModelImpl( | |||
| // bullet-featherstone and so setting them does not have any effect. | |||
| // The lower and uppper limit is supported via the | |||
There was a problem hiding this comment.
Typo in comment: "uppper" should be "upper".
Suggested change
| // The lower and uppper limit is supported via the | |
| // The lower and upper limit is supported via the |
Comment on lines
+831
to
+833
| if (joint->Axis()) | ||
| { | ||
| model->body->getLink(i).m_jointLowerLimit = |
There was a problem hiding this comment.
This change fixes a crash during SDF model construction for ball joints with no axis; please add a regression test that loads an SDF/world containing a ball joint without an <axis> using the bullet-featherstone engine and asserts ConstructWorld (or ConstructModel) succeeds without crashing.
iche033
approved these changes
Feb 12, 2026
Contributor
|
@Mergifyio backport gz-physics9 gz-physics8 gz-physics7 |
Contributor
✅ Backports have been createdDetails
|
mergify Bot
pushed a commit
that referenced
this pull request
Feb 12, 2026
) Signed-off-by: momo <2438833481@qq.com> (cherry picked from commit 2f8e332)
7 tasks
mergify Bot
pushed a commit
that referenced
this pull request
Feb 12, 2026
) Signed-off-by: momo <2438833481@qq.com> (cherry picked from commit 2f8e332)
7 tasks
mergify Bot
pushed a commit
that referenced
this pull request
Feb 12, 2026
) Signed-off-by: momo <2438833481@qq.com> (cherry picked from commit 2f8e332)
7 tasks
iche033
pushed a commit
that referenced
this pull request
Feb 13, 2026
) Signed-off-by: momo <2438833481@qq.com> (cherry picked from commit 2f8e332)
iche033
pushed a commit
that referenced
this pull request
Feb 13, 2026
) Signed-off-by: momo <2438833481@qq.com> (cherry picked from commit 2f8e332)
iche033
pushed a commit
that referenced
this pull request
Feb 13, 2026
) Signed-off-by: momo <2438833481@qq.com> (cherry picked from commit 2f8e332)
mderbaso-deepx
pushed a commit
to DeepX-inc/gz-physics
that referenced
this pull request
Apr 13, 2026
…azebosim#868) Signed-off-by: momo <2438833481@qq.com> (cherry picked from commit 2f8e332)
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
🦟 Bug fix
Fixes #864
Summary
Fixed a segmentation fault in the
Bullet Featherstoneplugin triggered by SDF models containing ball joints.Added a null pointer check for
joint->Axis()to prevent invalid access when loading joints that lack an axis definition.Checklist
codecheckpassed (See contributing)