In CPython 3.14, we introduced an alternative interpreter implementation. This implementation used [[musttail]] , an experimental C/C++ feature that tells the compiler to enforce tail calls. Against the previous interpreter using computed gotos/switch-case, the new interpreter style shows 2%--15% performance improvement (i.e. geometric mean running time), and is more resilient against certain types of compiler bugs. This feature is already supported by Clang, GCC, and MSVC, and is also the center of a draft proposal targeting C++29. In this talk, I’ll cover the story of getting this feature into the Python interpreter, our collaboration with compiler developers, and the potential wider impact on the C++ community. I’ll also cover interesting use cases of this feature other than for writing interpreters, such as for automatically generating a simple Just in Time (JIT) compiler.
Tooling Track sessions are sponsored by Optiver.
