gh-104621: Check for Incompatible Extensions in import_find_extension() (gh-107184)
This fixes a bug where incompatible modules could still be imported if attempted multiple times.
(cherry picked from commit 75c974f535)
Co-authored-by: Eric Snow <ericsnowcurrently@gmail.com>
Enforcing (optionally) the restriction set by PEP 489 makes sense. Furthermore, this sets the stage for a potential restriction related to a per-interpreter GIL.
This change includes the following:
* add tests for extension module subinterpreter compatibility
* add _PyInterpreterConfig.check_multi_interp_extensions
* add Py_RTFLAGS_MULTI_INTERP_EXTENSIONS
* add _PyImport_CheckSubinterpIncompatibleExtensionAllowed()
* fail iff the module does not implement multi-phase init and the current interpreter is configured to check
https://github.com/python/cpython/issues/98627
