Fixing the SketchUp Importer Crash on Blender 5.x (macOS)

Introduction

If you've ever tried importing a .skp file into Blender using the pyslapi addon, you probably know it's one of the only open-source options out there.

But if you tried it on Blender 5.0.1 on a Mac with Apple Silicon…

It just crashed. Instantly. No error dialog, no traceback — just gone.

I decided to dig in and fix it.

The Problem

When you install the addon and restart Blender 5.0.1 on macOS, the app crashes immediately with a SIGSEGV (segmentation fault).

The crash report pointed to:

EXC_BAD_ACCESS (SIGSEGV)

This happened during startup — before you even try to import anything. Blender was crashing just by loading the addon's compiled extension (sketchup.so).

What Caused It

The root cause turned out to be a Python ABI mismatch.

Here's the breakdown:

• Blender 5.0.1 bundles Python 3.11
• The old sketchup.so binary was compiled against older Python headers
• CPython 3.11 significantly redesigned its internal structs (especially PyCodeObject)
• The old binary had wrong struct offsets baked in

So when Python tried to validate the module on import, it was reading garbage memory — and crashed.

On top of that, the extension was built with Cython 0.29.x, which generates C code with known incompatibilities against CPython 3.11 internals.

How I Diagnosed It

Here's the debugging process I followed:

1. Checked the binary

file sketchup.so
# Mach-O 64-bit bundle arm64 ✓

The architecture was correct — this wasn't an Intel vs ARM issue.

2. Checked linked libraries

otool -L sketchup.so

Framework paths looked fine. @loader_path was set correctly for SketchUpAPI.framework.

3. Checked the ABI tag

The .so filename didn't include the standard cpython-311-darwin ABI tag. This was the first red flag — it meant the binary wasn't built specifically for Python 3.11.

4. Checked Blender's Python version

/Applications/Blender.app/Contents/Resources/5.0/python/bin/python3.11 -c \
  "import sys; print(sys.version)"
# Python 3.11.13

Blender ships Python 3.11, but the compiled extension wasn't built against 3.11 headers.

5. Inspected Cython artifacts

strings sketchup.so | grep "Cython"

Found references to old Cython runtime patterns — confirming it was built with Cython 0.29.x, which has known issues with CPython 3.11.

The Fix

The fix involved three things:

1. Recompiled with correct Python 3.11 headers

Blender's bundled Python doesn't ship development headers, so I used Homebrew's python@3.11 instead:

export PYTHON=$(brew --prefix python@3.11)/bin/python3.11
$PYTHON setup.py build_ext --inplace

This ensures the resulting .so has the correct struct offsets for CPython 3.11.

2. Upgraded Cython to 3.x

$PYTHON -m pip install "Cython>=3.0.0"

Cython 3.x generates C code that's fully compatible with CPython 3.11's redesigned internals.

3. Improved the build script

I rewrote build_release_macos.sh to:

• Auto-detect Blender's bundled Python version
• Verify ABI compatibility before building
• Fall back to Homebrew python@3.11 when Blender's Python lacks dev headers
• Run post-build verification to catch issues early
• Fix framework load paths with install_name_tool

I also added a safety check in setup.py that warns you if you accidentally build with the wrong Python version.

The Result

After recompiling:

/Applications/Blender.app/Contents/MacOS/Blender --background \
  --python-expr "import sketchup; print(sketchup.get_API_version())"

No crash. The module loads cleanly, and SketchUp files import as expected.

The Python Fixes (v0.25.1)

Before the ABI crash even became visible, the addon had Python-level bugs that crashed imports.

1. KeyError on Nested/Duplicate Components

The importer only tracked top-level component definitions, so nested components and auto-renamed duplicates (like ComponentName#1) caused a KeyError on lookup. I added a _resolve_component method that lazily discovers and registers unknown definitions at import time, replacing three direct dictionary lookups that would crash on any model with nested hierarchies.

I also fixed a broken except path in the proxy_dict class that raised a second KeyError instead of falling through.

2. Duplicate Processing Bug

A stray duplicate call to write_duplicateable_groups() caused every component to be processed twice — wasting time and potentially creating duplicate objects. Removed it.

3. Modernizing setup.py for Apple Silicon

Migrated from distutils (removed in Python 3.12) to setuptools, added rpath for framework resolution at runtime, and set -std=c++14 so the extension compiles natively on Apple Silicon without manual install_name_tool hacks.

Try It Out

If you're a Blender user on macOS who's been frustrated by the SketchUp importer crashing, give the latest release a try:

👉 Download the latest release

Quick install:

1. Download sketchup_importer_0.25.2_macos_arm64.zip
2. In Blender: Edit > Preferences > Add-ons > Install → select the zip
3. Enable Import-Export: Sketchup importer
4. Import via File > Import > Import Sketchup Scene (.skp)

Compatibility:

Final Thoughts

This was a classic case of a binary built against the wrong headers silently producing a working file — until the runtime ABI changed underneath it.

The lesson: always match your build environment to the target runtime. Especially with CPython, where internal struct layouts can change between minor versions.

If you run into issues or have feedback, feel free to open an issue or reach out. Happy blending! 🎨