We support fat builds of Python on macOS, in particular used for the "Universal 2" installers on macOS (configure --enable-universalsdk --with-universal-archs=universal2). This uses clang's builtin support for compiling multiple architectures in one go (e.g. clang -arch arm64 -arch x86_64 ...).

As far as I can see now the machinery for JIT (--enable-experimental-jit) does not support this at the moment.

On possible way to get this to work (untested and likely incomplete) is to generate multiple variants for jit_stencils.h when doing a fat build and generate an umbrella header that includes the right one:

// jit_stencils.h

#if defined(__arm64__)
#include "jit_stencils-arm64.h"
#elif defined(__x86_64__)
#include "jit_stencils-x86_64.h"
#endif

Linked PRs

• gh-114809: Support fat builds on macOS with the experimental JIT #115742
• GH-114809: Add support for macOS multi-arch builds with the JIT enabled #131751