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Segmentation Fault When Using Python 3 #32

#1

Hello Professor Hauser,

I have a problem where running my code in Python 3 gives me a segmentation fault but running my code using Python 2 works fine. Based on some debugging, it appears that the error occurs when reading the URDF file. Here is my code (which I have greatly simplified to try and figure out this issue), URDF file, and the error I get (using faulthandler).

Python Code:

import faulthandler

import klampt
FILEPATH = "./agrobot_sim.xml"

if __name__ == "__main__":
    faulthandler.enable()
    world = klampt.WorldModel()
    print("got world")
    res = world.readFile(FILEPATH)
    print("read file")
    robot = world.robot(0)

URDF:

<?xml version="1.0" encoding="utf-8"?>
<!-- =================================================================================== -->
<!-- |    This document was autogenerated by xacro from robot_controlsim_v2.xacro      | -->
<!-- |    EDITING THIS FILE BY HAND IS NOT RECOMMENDED                                 | -->
<!-- =================================================================================== -->
<robot name="ranch_rover">
  <!-- First link of the robot. Corresponds to the robot main frame. -->
  <link name="link_chassis">
    <pose> 0 0 0 0 0 0 </pose>
    <inertial>
      <mass value="24.5"/> 
      <origin rpy="0 0 0" xyz="0.0052 -0.0009 0.0050"/>
      <inertia ixx="0.729" ixy="0.0029" ixz="-0.0160" iyx="0.0029" iyy="0.4254" iyz="0.0028" izx="-0.0160" izy="0.0028" izz="1.008"/>
    </inertial>
    <collision>
      <geometry>
	<mesh filename="agrobot/link_chassis.STL" scale="0.001 0.001 0.001"/>
      </geometry>
      <origin rpy="0 0 0" xyz="0 0 0"/>
    </collision>
    <visual name="vis1">
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <mesh filename="agrobot/link_chassis.STL" scale="0.001 0.001 0.001"/>
      </geometry>
    </visual>
  </link>

  <!-- LINK_1 -->
  <link name="Link_1">
    <inertial>
      <origin rpy="0 0 0" xyz="2.74225442931497E-06 -0.00353778613018245 0.0515804512927737"/>
      <mass value="0.507852532624306"/>
      <inertia ixx="0.000305049101665729" ixy="1.46296943748327E-09" ixz="-1.23302173450347E-08" iyy="0.000527056723286848" iyz="4.68473207349431E-06" izz="0.000309137354236652"/>
    </inertial>
    <visual>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <mesh filename="agrobot/Link_1.STL"/>
      </geometry>
      <material name="">
        <color rgba="0.752941176470588 0.752941176470588 0.752941176470588 1"/>
      </material>
    </visual>
    <collision>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <mesh filename="agrobot/Link_1.STL"/>
      </geometry>
    </collision>
  </link>
  <joint name="Joint_1" type="revolute">
    <origin rpy="0 0 0" xyz="0.190 -0.033 0.196"/>
    <parent link="link_chassis"/>
    <child link="Link_1"/>
    <axis xyz="0 0 1"/>
    <limit effort="17" lower="-3.1415" upper="3.1415" velocity="40"/>
    <dynamics damping="0.0" friction="0.09"/>
  </joint>
  <transmission name="trans_Joint_1">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="Joint_1">
      <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
    </joint>
    <actuator name="motor_Joint_1">
      <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>
  <!-- LINK_2 -->
  <link name="Link_2">
    <inertial>
      <origin rpy="0 0 0" xyz="0.058405779904307 2.0203040740352E-08 0.0339456863545732"/>
      <mass value="0.81308899959476"/>
      <inertia ixx="0.000388392439322651" ixy="-9.54214032854378E-10" ixz="1.27795112061735E-05" iyy="0.00467218660610504" iyz="-8.84832562194152E-11" izz="0.00496730197895087"/>
    </inertial>
    <visual>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <mesh filename="agrobot/Link_2.STL"/>
      </geometry>
      <material name="">
        <color rgba="0.752941176470588 0.752941176470588 0.752941176470588 1"/>
      </material>
    </visual>
    <collision>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <mesh filename="agrobot/Link_2.STL"/>
      </geometry>
    </collision>
  </link>
  <joint name="Joint_2" type="revolute">
    <origin rpy="-1.5707963267949 0 3.14159265358979" xyz="0 -0.019 0.0545"/>
    <parent link="Link_1"/>
    <child link="Link_2"/>
    <axis xyz="0 0 1"/>
    <limit effort="17" lower="-3.1415" upper="0" velocity="40"/>
    <dynamics damping="0.0" friction="0.09"/>
  </joint>
  <transmission name="trans_Joint_2">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="Joint_2">
      <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
    </joint>
    <actuator name="motor_Joint_2">
      <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>
  <!-- LINK_3 -->
  <link name="Link_3">
    <inertial>
      <origin rpy="0 0 0" xyz="0.232598222729073 -9.20818372995846E-07 -0.00955342978657184"/>
      <mass value="0.336944931620173"/>
      <inertia ixx="3.67648841212008E-05" ixy="-9.59389619481419E-11" ixz="-1.81657115526022E-06" iyy="0.00138520509069701" iyz="2.76629218451524E-12" izz="0.00140450563412969"/>
    </inertial>
    <visual>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <mesh filename="agrobot/Link_3.STL"/>
      </geometry>
      <material name="">
        <color rgba="0.752941176470588 0.752941176470588 0.752941176470588 1"/>
      </material>
    </visual>
    <collision>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <mesh filename="agrobot/Link_3.STL"/>
      </geometry>
    </collision>
  </link>
  <joint name="Joint_3" type="revolute">
    <origin rpy="0 0 -1.5708" xyz="0.352 0 0.05275"/>
    <parent link="Link_2"/>
    <child link="Link_3"/>
    <axis xyz="0 0 1"/>
    <limit effort="17" lower="-1.0472" upper="2.6" velocity="40"/>
    <dynamics damping="0.0" friction="0.09"/>
  </joint>
  <transmission name="trans_Joint_3">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="Joint_3">
      <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
    </joint>
    <actuator name="motor_Joint_3">
      <hardwareInterface>hardware_interface/EffortJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>
  <!-- LINK_4 -->
  <link name="Link_4">
    <inertial>
      <origin rpy="0 0 0" xyz="0.0322792079054944 0.0215434702240224 1.30818635455249E-05"/>
      <mass value="0.213921465907275"/>
      <inertia ixx="5.72875335800106E-05" ixy="-2.1737619349779E-09" ixz="-2.22685486617804E-08" iyy="2.96741933821847E-05" iyz="1.83334792134304E-09" izz="6.54238610234211E-05"/>
    </inertial>
    <visual>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <mesh filename="agrobot/Link_4.STL"/>
      </geometry>
      <material name="">
        <color rgba="0.752941176470588 0.752941176470588 0.752941176470588 1"/>
      </material>
    </visual>
    <collision>
      <origin rpy="0 0 0" xyz="0 0 0"/>
      <geometry>
        <mesh filename="agrobot/Link_4.STL"/>
      </geometry>
    </collision>
  </link>
  <joint name="Joint_4" type="revolute">
    <origin rpy="0 0 0" xyz="0.32 0 0"/>
    <parent link="Link_3"/>
    <child link="Link_4"/>
    <axis xyz="0 0 1"/>
    <limit effort="2.268" lower="-1.571" upper="1.571" velocity="0.319"/>
    <dynamics damping="0.0" friction="0.09"/>
  </joint>
  <transmission name="trans_Joint_4">
    <type>transmission_interface/SimpleTransmission</type>
    <joint name="Joint_4">
      <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
    </joint>
    <actuator name="motor_Joint_4">
      <hardwareInterface>hardware_interface/VelocityJointInterface</hardwareInterface>
      <mechanicalReduction>1</mechanicalReduction>
    </actuator>
  </transmission>

</robot>

Error:

Screenshot from 2020-12-29 00-41-21.png

I'm fairly new to coding and have been trying to debug this for quite some time now. I need to use Python 3 because I will be using other libraries that are only compatible with Python 3. Do you know what the issue might be? If not, would you happen to have any recommendations on debugging this?

Please let me know if you need any more information. Thank you!

Sincerely,
Ryan

  • replies 4
  • views 1.3K
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#2

When segmentation faults occur, the best output you can provide to help diagnose the problem is to use gdb to get a stack trace.

  1. Install gdb (eg through apt-get)
  2. Run “gdb python“
  3. At the prompt, enter “run test.py”
  4. At the crash, enter “backtrace”.
  5. copy and paste the output here.
ryanp543 · Author
#3

Thank you for the quick response! I really appreciate it. A copy of the output is here:

Screenshot from 2020-12-29 02-42-38.png
#4

This looks like a problem with whatever version of Assimp you have installed on your machine, but I've never seen the issue before. Could you report the version of your OS and your Assimp library?

The latest version of Klamp't (0.8.5) is built with the latest version of Assimp (4.x) whereas prior versions were built with Assimp 3.0.x. You might try upgrading or downgrading the Assimp version (the apt-get package name is "libassimp-dev").

ryanp543 · Author

My version of Assimp is 4.1.0, my version of Klamp't is 0.8.1 (installed with pip3), and my version of Ubuntu is 18.04.5. I'll keep upgrading/downgrading to see if there's a mismatch somewhere.

EDIT: For some reason, when I remove mentions of the STL files in the URDF, my code works fine now in Python 3. Strange. It looks like this post https://gitq.com/krishauser/Klampt/topics/20/getting-segfault-when-loading-a-urdf also experienced the same issue.

I think I can make do without the STL files for now, though being able to keep the STL references in the URDF would be nice. Thanks!