Joint::childLink not loaded correctly

[osrf-migration]

Original report (archived issue) by John Hsu (Bitbucket: hsu, GitHub: hsu).

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Currently Joint::LoadImpl has an error in its logic such that if parentLink is not NULL, childLink is not assigned. This is done in error, the code should look like below:

hg diff gazebo/physics/Joint.cc 
diff -r 3cafd154f538560150bda6ab3468ccfb35f70ca8 gazebo/physics/Joint.cc
--- a/gazebo/physics/Joint.cc	Thu Nov 07 10:51:37 2013 -0800
+++ b/gazebo/physics/Joint.cc	Thu Nov 07 12:05:44 2013 -0800
@@ -159,9 +159,11 @@
 
   if (this->parentLink)
     this->parentLink->AddChildJoint(boost::static_pointer_cast<Joint>(myBase));
-  else if (this->childLink)
+
+  if (this->childLink)
     this->childLink->AddParentJoint(boost::static_pointer_cast<Joint>(myBase));
-  else
+
+  if (!this->parentLink && !this->childLink)
     gzthrow("both parent and child link do no exist");
 
   // setting anchor relative to gazebo child link frame position

[osrf-migration]

Original comment by John Hsu (Bitbucket: hsu, GitHub: hsu).

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pull request #772 has a fix 9b5e7e8.

we need a separate pull request for gazebo 1.9.

[osrf-migration]

Original comment by Nate Koenig (Bitbucket: Nathan Koenig).

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This definitely looks wrong, but it also looks like it was done on purpose. Is there a scenario in which the original code fails?

[osrf-migration]

Original comment by John Hsu (Bitbucket: hsu, GitHub: hsu).

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For example, for a robot like atlas, any of the robot's joints Joint::GetParent() will return an empty pointer, but we expect each (except pelvis) of the links in the robot to have a parent link. Example test usage, without this fix, parent is NULL in this test except for the joints that attach each foot to the world.

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

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I don't think it was done on purpose. I think I just botched the logic in pull request #329. We should add a test for this (maybe somewhere in Joint_TEST).

[osrf-migration]

Original comment by Nate Koenig (Bitbucket: Nathan Koenig).

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Nice detective work. I retract my concern.

[osrf-migration]

Original comment by John Hsu (Bitbucket: hsu, GitHub: hsu).

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pull request #820 for gazebo_1.9, after that, we should merge it downstream into gazebo_2.0, gazebo_2.1 and default.

[osrf-migration]

Original comment by John Hsu (Bitbucket: hsu, GitHub: hsu).

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merged pull request #820
created pull request #833 as a reminder to merge gazebo_1.9 into gazebo_2.0

[osrf-migration]

Original comment by Steve Peters (Bitbucket: Steven Peters, GitHub: scpeters).

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• changed state from "new" to "resolved"

pull request #820 and pull request #833 have both been merged.

[osrf-migration]

Original comment by Nate Koenig (Bitbucket: Nathan Koenig).

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• set version to "all"

[osrf-migration]

Original comment by Nate Koenig (Bitbucket: Nathan Koenig).

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• changed state from "resolved" to "closed"