Fix potential segfault errors

[mindflayer]

Summary

Fixes several C-level memory safety issues in ToGo's Cython bindings that could surface as segfaults under planner-style workloads with heavy geometry extraction, GEOS operations, and garbage collection pressure.

What changed

• Clone borrowed TG pointers before exposing them as Python-owned wrappers:
  • Geometry.line()
  • Geometry.poly()
  • Poly.exterior
  • Poly.hole(...)
  • internal Ring.from_ptr(...) / Poly._from_c_poly(...) paths
• Add defensive NULL pointer checks before wrapping TG pointers.
• Initialize Geometry.geom explicitly in Geometry.__cinit__.
• Check clone failures and raise Python exceptions instead of creating invalid wrapper objects.
• Make C buffer allocation paths exception-safe with try/finally.
• Add checked Python-to-C count conversion before passing sequence lengths into TG APIs.
• Improve cleanup in Geometry.unary_union(...) by destroying GEOS geometries on all success/error paths.
• Handle empty meters-grid conversions in the ToGo wrapper layer by cloning empty geometries instead of calling into TGX with empty component arrays.
• Add regression tests for:
  • wrapper objects surviving parent Geometry / Poly garbage collection
  • empty geometry meters-grid round trips

Why

The previous implementation returned Python wrapper objects around borrowed C pointers owned by parent geometries. If the parent object was garbage-collected while the child wrapper remained in use, later calls could dereference freed memory and crash.

This was especially likely in long-running planner integrations that repeatedly extract rings, polygons, boundaries, or line strings from temporary geometries.

Validation

• Built successfully with:

  make build-wheel

[Copilot]

Pull request overview

This PR hardens ToGo’s Cython bindings against C-level lifetime and allocation hazards that can manifest as segfaults under heavy geometry extraction / GC pressure. It primarily shifts wrapper creation toward cloning TG objects (so Python wrappers own their C pointers), adds defensive NULL checks, and improves exception-safety/cleanup around C allocations and GEOS operations.

Changes:

• Clone borrowed TG pointers before returning Python wrapper objects; add NULL-pointer and clone-failure checks.
• Make several C allocation/write paths exception-safe via try/finally, plus checked Python→C count conversion for TG APIs.
• Add regression tests covering wrapper survival after parent GC and empty-geometry meters-grid round trips.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
togo.pyx	Adds pointer-cloning/NULL checks and improves cleanup/exception-safety across multiple TG/GEOS interop paths.
tests/test_poly.py	Adds a GC regression test ensuring Poly.exterior remains usable after parent collection.
tests/test_geometry.py	Adds GC regression tests for accessors and verifies meters-grid conversions for empty geometries.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 6 comments.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.