STINNER Victor <vstin...@python.org> added the comment:
Ok, I can reproduce the crash on the 3.9 branch using: ./python repro.py. The first problem is that astmodule_clear() doesn't reset the initiallized member: add "state->initialized = 0;". The _ast module is special. Not only it has regular module function which access the module state, it also has 3 functions in C APIs which are called directly: * PyAST_Check() * PyAST_mod2obj() * PyAST_obj2mod() These functions require to have access to the _ast module. In Python 3.9, I chose to use a global state, as it was done in Python 3.8. If sys.modules['_ast'] is cleared and then _ast is imported again, _PyState_AddModule() is called to store the new _ast module instance which calls astmodule_clear() on the old module instance. The problem is that when astmodule_clear() is called, the new instance is already created and so exposes the "old" _ast.AST type. 1) import _ast: call init_types() which creates AST type #1 2) del sys.modules['_ast] 3) import _ast: create a new module which exposes AST type #1 3) import _ast: also clears the old module (_PyState_AddModule()) which calls astmodule_clear() 4) Calling PyAST_Check() calls init_types() which creates AST type #2: PyAST_Check() returns false, since AST type #1 and AST type #2 are different -- In the master branch, I modified PyAST_Check(), PyAST_mod2obj() and PyAST_obj2mod() to import the _ast module and get the state from the module. The state is not global in master. For 3.9, I'm not sure what is the best option: * Backport master changes (not well tested yet, but is it worse than this known crash?) * Never clear the state: leak references at Python exit. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue41261> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
