8000 bpo-36389: _PyObject_CheckConsistency() now also works in release mode by vstinner · Pull Request #16612 · python/cpython · GitHub
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Merged
merged 1 commit into from
Oct 7, 2019
Merged

bpo-36389: _PyObject_CheckConsistency() now also works in release mode #16612

merged 1 commit into from
Oct 7, 2019

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vstinner
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@vstinner vstinner commented Oct 7, 2019

bpo-36389, bpo-38376: Modify the following functions to also work in
release mode:

  • _PyDict_CheckConsistency()
  • _PyObject_CheckConsistency()
  • _PyType_CheckConsistency()
  • _PyUnicode_CheckConsistency()

The main function _PyObject_CheckConsistency() can be used for
debugging purpose, like crash in visit_decref() of the GC.

_PyBytesWriter_CheckConsistency() now returns 1 and is only used with
assert().

https://bugs.python.org/issue36389

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vstinner commented Oct 7, 2019

I would like to push this change into 3.8 since https://bugs.python.org/issue36389 was designed for Python 3.8.

@Yhg1s Yhg1s requested a review from ambv October 7, 2019 10:40
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Yhg1s commented Oct 7, 2019

Roping in the 3.8 release manager for the question of whether this should go into 3.8.0.

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vstinner commented Oct 7, 2019

This change mostly impacts the debugging experience. It doesn't change Python in release mode: modified functions only becomes available in release mode, but are never called.

@Yhg1s: Thanks for your review. I agree that "define ASSERT" is confusing. I renamed my macros to "CHECK" as you suggested.

I also included other fixes for these debug functions.

bpo-36389, bpo-38376: The _PyObject_CheckConsistency() function is
now also available in release mode. For example, it can be used to
debug a crash in the visit_decref() function of the GC.

Modify the following functions to also work in release mode:

* _PyDict_CheckConsistency()
* _PyObject_CheckConsistency()
* _PyType_CheckConsistency()
* _PyUnicode_CheckConsistency()

Other changes:

* _PyMem_IsPtrFreed(ptr) now also returns 1 if ptr is NULL
  (equals to 0).
* _PyBytesWriter_CheckConsistency() now returns 1 and is only used
  with assert().
* Reorder _PyObject_Dump() to write safe fields first, and only
  attempt to render repr() at the end.
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vstinner commented Oct 7, 2019

@vstinner vstinner removed the needs backport to 3.8 label now

I wrote a minimum fix for 3.8: PR #16623.

I may backport this change to 3.8, but only after the final 3.8.0 release. We can discuss that later ;-)

@vstinner vstinner merged commit 6876257 into python:master Oct 7, 2019
@vstinner vstinner deleted the check_consistency branch October 7, 2019 16:42
vstinner added a commit that referenced this pull request Oct 15, 2019
* bpo-36389: _PyObject_CheckConsistency() available in release mode (GH-16612)

bpo-36389, bpo-38376: The _PyObject_CheckConsistency() function is
now also available in release mode. For example, it can be used to
debug a crash in the visit_decref() function of the GC.

Modify the following functions to also work in release mode:

* _PyDict_CheckConsistency()
* _PyObject_CheckConsistency()
* _PyType_CheckConsistency()
* _PyUnicode_CheckConsistency()

Other changes:

* _PyMem_IsPtrFreed(ptr) now also returns 1 if ptr is NULL
  (equals to 0).
* _PyBytesWriter_CheckConsistency() now returns 1 and is only used
  with assert().
* Reorder _PyObject_Dump() to write safe fields first, and only
  attempt to render repr() at the end.

(cherry picked from commit 6876257)

* bpo-36389: Fix _PyBytesWriter in release mode (GH-16624)

Fix _PyBytesWriter API when Python is built in release mode with
assertions.

(cherry picked from commit 60ec6ef)

* bpo-38070: Enhance visit_decref() debug trace (GH-16631)

subtract_refs() now pass the parent object to visit_decref() which
pass it to _PyObject_ASSERT(). So if the "is freed" assertion fails,
the parent is used in debug trace, rather than the freed object. The
parent object is more likely to contain useful information. Freed
objects cannot be inspected are are displayed as "<object at xxx is
freed>" with no other detail.

(cherry picked from commit 4d5f94b)

* Fix also a typo in PYMEM_DEADBYTE macro comment

* bpo-36389: Add newline to _PyObject_AssertFailed() (GH-16629)

Add a newline between the verbose object dump and the Py_FatalError()
logs for readability.

(cherry picked from commit 7775349)
jacobneiltaylor pushed a commit to jacobneiltaylor/cpython that referenced this pull request Dec 5, 2019
…thonGH-16612)

bpo-36389, bpo-38376: The _PyObject_CheckConsistency() function is
now also available in release mode. For example, it can be used to
debug a crash in the visit_decref() function of the GC.

Modify the following functions to also work in release mode:

* _PyDict_CheckConsistency()
* _PyObject_CheckConsistency()
* _PyType_CheckConsistency()
* _PyUnicode_CheckConsistency()

Other changes:

* _PyMem_IsPtrFreed(ptr) now also returns 1 if ptr is NULL
  (equals to 0).
* _PyBytesWriter_CheckConsistency() now returns 1 and is only used
  with assert().
* Reorder _PyObject_Dump() to write safe fields first, and only
  attempt to render repr() at the end.
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