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bpo-34720: Fix test_importlib.test_bad_traverse for AIX #9391

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merged 6 commits into from
Feb 17, 2019
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bpo-34720: Fix test_importlib.test_bad_traverse for AIX #9391

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40ec805
Fix test_importlib.test_bad_traverse for AIX
aixtools Sep 18, 2018
05469e1
Fix whitespace
aixtools Sep 18, 2018
ce014f3
News not required
aixtools Oct 29, 2018
b7c9b9a
Assert m_state != NULL to mimic transversal functions that do not cor…
aixtools Dec 26, 2018
4a1215b
Tweak NEWS entry wording.
ncoghlan Feb 17, 2019
739b9a8
Add comment explaining why the assert() is OK
ncoghlan Feb 17, 2019
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12 changes: 12 additions & 0 deletions Modules/_testmultiphase.c
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Original file line number Diff line number Diff line change
Expand Up @@ -624,6 +624,18 @@ bad_traverse(PyObject *self, visitproc visit, void *arg) {
testmultiphase_state *m_state;

m_state = PyModule_GetState(self);

#ifdef _AIX
/*
* AIX does not have a segmentation fault is a NULL pointer is accessed
* In order to mimic other systems that would crash if &(m_state->integer) == NULL
* force a non-zero exit status
*/
if (&(m_state->integer) == NULL) {
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Perhaps this could replace the Py_VISIT(m_state->integer); call on all platforms, thus avoiding the #ifdef?

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Calling Py_VISIT(m_state->integer) is the purpose of this test.

But I wondering if it could be better to just skip the test on AIX in Python code.

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Obviously, I cannot "decide" what is "cleaner" - letting the test run, but have a modification in the C code the test calls, or having an "SkipIf" in the test (and move the comment to the test, so it is clear why the skip is needed).

I will make the recommended change.

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This test case originated from c2b0b12, and the new behaviour it's actually attempting to verify is:

  1. In debug mode, module creation automatically invokes the registered traverse function (for eager detection of problematic traversal function definitions)
  2. When the traversal function isn't checking correctly for a valid module state, the module creation fails

Actually implementing a valid traversal function here isn't overly important, as the module using it never actually gets created.

So I think @taleinat's right that this bad traversal function can be simplified to avoid the #ifdef, but I think it can be simplified all the way to being just:

m_state = PyModule_GetState(self);
/* The following assertion mimics any traversal function that doesn't correctly handle
 * the case during module creation where the module state hasn't been created yet.
 */
assert(m_state != NULL);
Py_VISIT(m_state->integer);
return 0;

That way the case of interest will always fail on the assert() call, and never even attempt to dereference the pointer.

exit(255);
}
#endif

Py_VISIT(m_state->integer);
return 0;
}
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