Python-C++ Bindings Meeting

Tuesday 31 Mar 2026, 16:00 → 17:00 Europe/Zurich

Aaron Jomy (CERN)

Discussion on developments in Python-C++ bindings surrounding the Cppyy project, and broader interactive C++ as a service based on the CppInterOp project.

Roundtable:

Vassil:
  * Released CppInterOp 1.9 with the help of Aaron
  * A lot of AD work on Clad (outside the scope of this meeting)

Jonas:
  * Continuing to fix problems in the CPython extension related to the buffer
    protocol
  * Will address the std::array iterator problem soon, as it was independently
    reported by a physicist on GitHub:
    https://github.com/root-project/root/issues/21732
  * Support building other ROOT CPython extensions (besides cppyy) with the
    Limited CPython API: https://docs.python.org/3/c-api/stable.html

Vincenzo:
  * Not much Python related working on compression studies for ROOT

Aaron:
  * Working on the cppyy ROOT migration and getting patches into the
    compiler-research forks.
  * Upstreamed many patches to cppyy from the ROOT side, including forbidding
    mutable pointer references as arguments (T*&)
  * Patching CppInterOp 1.9 for Windows

Emery:
  * Isolated reproducer for three bugs that we still see and talked about 2
    weeks ago. I'll report them on GitHub soon.
  * No other clear blockers for the integration in CTC
  * Where should I open the PR with the test improvements?
    * Aaron: still the compiler research forks.
  * Are you interested in putting the Bazel build setup also in the CppJIT repository?
    * Aaron: yes, we heard also at using std::cpp that people were quite
      interested in hermetic builds with Bazel, so we are generally interested
      in it! It it coexists well with CMake and can be integrated in the CI, it
      would be a very welcome contribution. We can maintain it on a best errort basis.

 

Closing meeting after 30 mins.

16:00 → 16:30 Round Table

16:30 → 17:00 AOB