There’s a number of things that affect the compatibility between an extension module and the Python interpreter. Just listing a few:
- Free-threading
- debug/no-debug
- Py_TRACE_REFS
- Python version
Because of the way the Windows headers are distributed, it’s currently pretty easy to build an extension module with the “free-threading” filename tag, but built again non-freethreaded header. This obviously immediately crashes. The other incompatibilities are less easy to do by mistake, but may still be worthwhile to check.
I think I’ve managed to hack something together in Cython that checks many of these parameters and raises an exception if they don’t match without manipulating Python objects in directly C (i.e. it only uses bits of the ABI which don’t change in the different build modes). The idea being that users are able to receive an ImportError telling them that their extension doesn’t match the interpreter rather than a mystery crash.
However, I was wondering if the Python interpreter could provide an interface to do this check that would be more robust than my hacked-together one. It’d probably want to be extensible so something like:
int Py_ABI_Check(int major_version, int minor_version, unsigned long flags);
where flags is built up by something like:
Py_ABI_FLAGS = 0 |
#if Py_DEBUG
1 |
#endif
#if Py_GIL_DISABLED
2 |
#endif
#if Py_TRACE_REFS
4
#endif
// etc
The idea is that you could write
PyObject *PyInit_module_name(void) {
if (Py_ABI_Check(PY_MAJOR_VERSION, PY_MINOR_VERSION, Py_ABI_FLAGS) < 0) {
return NULL;
}
return &moduledef;
}
and get a sensible (and cheap) error message if the interpreter doesn’t match. Obviously it wouldn’t be compulsory for extension authors to do this, but it might be a useful tool to have.
. I was mainly proposing to diagnose some common cases rather than every possible combination.