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Segfault related to attach by reference #2482

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jjyyxx opened this issue Mar 7, 2025 · 0 comments
Open
2 tasks done

Segfault related to attach by reference #2482

jjyyxx opened this issue Mar 7, 2025 · 0 comments
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@quagla
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@jjyyxx
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jjyyxx commented Mar 7, 2025 •
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Intro

Hi!

I am a graduate student at HKU, I use MuJoCo for my research on robotic manipulation.

My setup

MuJoCo 3.3.0, Python and C, Linux

What's happening? What did you expect?

See snippets below. Both snippets show segfault.

Also, when spec2 is compiled and to_xml before detaching, the result contains two levels of default, making MJCF invalid.

Steps for reproduction

Run snippet below.

Minimal model for reproduction

No response

Code required for reproduction

Case 1 (somehow cannot garbage collect *2?):

import mujoco
spec1 = mujoco.MjSpec.from_string("""
<mujoco>
<worldbody>
    <body name="a"/>
</worldbody>
</mujoco>
""")
spec2 = mujoco.MjSpec()
body1 = spec1.body('a')
frame2 = spec2.worldbody.add_frame()
body2 = frame2.attach_body(body1)
spec2.compile()
del frame2
del body2
del spec2
spec1.compile()

Case 2 (cannot detach after attaching then detaching from another spec)

import mujoco
spec1 = mujoco.MjSpec.from_string("""
<mujoco>
<worldbody>
    <body name="a"/>
</worldbody>
</mujoco>
""")
spec2 = mujoco.MjSpec()
body1 = spec1.body('a')
frame2 = spec2.worldbody.add_frame()
body2 = frame2.attach_body(body1)
spec2.detach_body(body2)
spec2.compile()
spec1.detach_body(body1)
spec1.compile()

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@jjyyxx @quagla