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gh-105927: PyImport_AddModule() uses _PyWeakref_GET_REF()#106001
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -12,6 +12,7 @@ | ||
| #include "pycore_pymem.h" // _PyMem_SetDefaultAllocator() | ||
| #include "pycore_pystate.h" // _PyInterpreterState_GET() | ||
| #include "pycore_sysmodule.h" // _PySys_Audit() | ||
| #include "pycore_weakref.h" // _PyWeakref_GET_REF() | ||
| #include "marshal.h" // PyMarshal_ReadObjectFromString() | ||
| #include "importdl.h" // _PyImport_DynLoadFiletab | ||
| #include "pydtrace.h" // PyDTrace_IMPORT_FIND_LOAD_START_ENABLED() | ||
| @@ -373,15 +374,30 @@ PyImport_AddModuleObject(PyObject *name) | ||
| return NULL; | ||
| } | ||
| // gh-86160: PyImport_AddModuleObject() returns a borrowed reference. | ||
| // Create a weak reference to produce a borrowed reference, since it can | ||
| // become NULL. sys.modules type can be different than dict and it is not | ||
| // guaranteed that it keeps a strong reference to the module. It can be a | ||
| // custom mapping with __getitem__() which returns a new object or removes | ||
| // returned object, or __setitem__ which does nothing. There is so much | ||
| // unknown. With weakref we can be sure that we get either a reference to | ||
| // live object or NULL. | ||
| // | ||
| // Use PyImport_AddModuleRef() to avoid these issues. | ||
| PyObject *ref = PyWeakref_NewRef(mod, NULL); | ||
| Py_DECREF(mod); | ||
| if (ref == NULL) { | ||
| return NULL; | ||
| } | ||
| mod = _PyWeakref_GET_REF(ref); | ||
| Py_DECREF(ref); | ||
| Py_XDECREF(mod); | ||
| if (mod == NULL && !PyErr_Occurred()) { | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others.Learn more. I am not sure that comparing mod with NULL after Py_XDECREF does not have an undefined behavior. AFAIK, you can do nothing with a pointer to released memory, not even compare it with NULL. There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others.Learn more. See comments of my PR#105998: IMO most of this code is useless and can be removed. | ||
| PyErr_SetString(PyExc_RuntimeError, | ||
| "sys.modules does not hold a strong reference " | ||
| "to the module"); | ||
| } | ||
| return mod; /* borrowed reference */ | ||
| } | ||