Signals.SIGSEGV: 11

[Cyrus]

Greetings! I'm a new member. Pleasure meeting you.

I configure and build ns3-3.47 with examples and tests and Python bindings, but running first.py example keeps running into SIGSEGV. I suppose this is a common issue for new users, but I have not been able to find the problem or find a related conversation in this group. Thanks for your help.

This occurs on both:
- Ubuntu 24.04 on WSL2 with Python 3.12
- Ubuntu 25.10 with Python 3.13

Dependencies including cppyy and related packages are all the latest versions.

[Urval Kheni]

This SIGSEGV issue is usually caused by an incompatible cppyy version. For ns-3.47, the Python bindings are only tested with:
cppyy==3.5.0
Using newer versions (e.g., 3.6.0+) can cause segmentation faults due to internal API changes.

Fix:
pip uninstall cppyy
pip install cppyy==3.5.0
After that, rebuild ns-3 and run the example again.
Also, since you're using Python 3.12/3.13, note that ns-3 Python bindings are not fully validated on newer Python versions yet. If the issue persists, try Python 3.10 or 3.11.
This is also mentioned in the ns-3.47 release notes.

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[Cyrus]

Thanks, Urval.

My cppyy version is 3.5.0 already -- it is the latest stable version and the manual mentions that it was tested.

But with regards to the Python version, please note that this segfault is occurring in the first line (import ns) of the very first Python example (first.py) one would run after installing ns3. And I tried Python 3.13 and 3.12, and also tried ns3-3.46 or ns3-3.45, and still observed the same issue. I think either I'm missing something, or the manual should mention that Python 3.12/3.13 simply do not work. I mean this issue should be too common to be overlooked if one runs to error in the first line of the first Python example.

Thanks.

[Gabriel Ferreira]

Probably some issue that was already fixed upstream. The latest passing job is https://gitlab.com/nsnam/ns-3-dev/-/jobs/14183607675
If you want to help diagnose the issue, enable sanitizers and rerun. It should tell you how it crashed.
./ns3 configure --enable-sanitizers && ./ns3 run first.py