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GeezerVison is showing github.com — bpo-43541: Fix PyEval_EvalCodeEx() regression by vstinner · Pull Request #24918 · python/cpython

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@vstinner

@vstinner vstinner commented Mar 18, 2021 •
edited by bedevere-bot
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  • Remove an assertion which required CO_NEWLOCALS and CO_OPTIMIZED
    code flags. It is ok to call this function on a code with these
    flags set.
  • Fix reference counting on builtins: remove Py_DECREF().
    Fix regression introduced in the
    commit 46496f9.

Add also a comment to document that _PyEval_BuiltinsFromGlobals()
returns a borrowed reference.

https://bugs.python.org/issue43541

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@vstinner
vstinner requested a review from markshannon as a code owner March 18, 2021 11:43
@the-knights-who-say-ni the-knights-who-say-ni added the CLA signed label Mar 18, 2021
@bedevere-bot bedevere-bot added the awaiting core review label Mar 18, 2021
@vstinner
bpo-43541: Fix PyEval_EvalCodeEx() regression
ce1aecc 
* Remove an assertion which required CO_NEWLOCALS and CO_OPTIMIZED
  code flags. It is ok to call this function on a code with these
  flags set.
* Fix reference counting on builtins: remove Py_DECREF().
  Fix regression introduced in the
  commit 46496f9.

Add also a comment to document that _PyEval_BuiltinsFromGlobals()
returns a borrowed reference.
@markshannon

markshannon commented Mar 18, 2021

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Why not have _PyEval_BuiltinsFromGlobals() return a strong reference?
Returning borrowed references is always risky.

Otherwise, looks good.
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@vstinner

vstinner commented Mar 18, 2021

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Why not have _PyEval_BuiltinsFromGlobals() return a strong reference? Returning borrowed references is always risky.

Before my 46496f9 change, _PyEval_BuiltinsFromGlobals() could call PyDict_New() sometimes: strong reference. With my change, it doesn't have to create a new strong reference anymore. So I chose to return a borrowed reference.

But I tried to keep a strong reference as soon as possible where it looks relevant. I compared with Python 3.9 behavior which doesn't hold strong references while using builtins.

I know that there are some crazy ways of crashing Python caused by borrowed references, but in general it's fine and Py_INCREF/Py_DECREF has an impact on performance. For example, https://bugs.python.org/issue15108 is a bug but it was closed as "not a bug". If someone spots a dangerous usage of builtins, INCREF/DECREF can be added around the usage.
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@vstinner
vstinner merged commit fc980e0 into python:master Mar 18, 2021
@bedevere-bot bedevere-bot removed the awaiting core review label Mar 18, 2021
@vstinner
vstinner deleted the eval_code_ex branch March 18, 2021 13:51
@vstinner

vstinner commented Mar 18, 2021

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I merged my PR.

Otherwise, looks good.

Thanks for the review Mark!
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@markshannon

markshannon commented Mar 18, 2021

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Using a strong reference would have no negative impact on performance, since PyFunction_NewWithQualName needs to increment the refcount anyway. All the other uses are in legacy API where we don't care about performance.
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jab added a commit to jab/cpython that referenced this pull request Mar 20, 2021
@jab
Merge branch 'master' into justin39/aiter-c
97d06e5 
* master: (129 commits)
  bpo-43452: Micro-optimizations to PyType_Lookup (pythonGH-24804)
  bpo-43517: Fix false positive in detection of circular imports (python#24895)
  bpo-43494: Make some minor changes to lnotab notes (pythonGH-24861)
  Mention that code.co_lnotab is deprecated in what's new for 3.10. (python#24902)
  bpo-43244: Remove symtable.h header file (pythonGH-24910)
  bpo-43466: Add --with-openssl-rpath configure option (pythonGH-24820)
  Fix a typo in c-analyzer (pythonGH-24468)
  bpo-41561: Add workaround for Ubuntu's custom security level (pythonGH-24915)
  bpo-43521: Allow ast.unparse with empty sets and NaN (pythonGH-24897)
  bpo-43244: Remove the PyAST_Validate() function (pythonGH-24911)
  bpo-43541: Fix PyEval_EvalCodeEx() regression (pythonGH-24918)
  bpo-43244: Fix test_peg_generators on Windows (pythonGH-24913)
  bpo-39342: Expose X509_V_FLAG_ALLOW_PROXY_CERTS in ssl module (pythonGH-18011)
  bpo-43244: Fix test_peg_generator for PyAST_Validate() (pythonGH-24912)
  bpo-42128: Add 'missing :' syntax error message to match statements (pythonGH-24733)
  bpo-43244: Add pycore_ast.h header file (pythonGH-24908)
  bpo-43244: Rename pycore_ast.h to pycore_ast_state.h (pythonGH-24907)
  Remove unnecessary imports in the grammar parser (pythonGH-24904)
  bpo-35883: Py_DecodeLocale() escapes invalid Unicode characters (pythonGH-24843)
  Add PEP 626 to what's new in 3.10. (python#24892)
  ...
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@markshannon markshannon Awaiting requested review from markshannon

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4 participants

@vstinner @markshannon @the-knights-who-say-ni @bedevere-bot
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