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gh-104619: never leak comprehension locals to outer locals() #104637

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merged 1 commit into from
May 19, 2023

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@carljm carljm commented May 19, 2023

The initial implementation of PEP 709 didn't bother to clear comprehension locals after an inlined comprehension, if the name was a global outside the comprehension. This was purely an optimization to save a couple extra instructions in this case; it didn't seem necessary to clear the comprehension value, since outer references to the name would use LOAD_GLOBAL anyway and not see the value in fastlocals.

But it is necessary to clear the comprehension local even in this case, because otherwise it will still show up in locals(), or in debugger usage, outside of the comprehension.

@JelleZijlstra JelleZijlstra merged commit 70c7796 into python:main May 19, 2023
carljm added a commit to gsallam/cpython_with_perfmap_apii that referenced this pull request May 20, 2023
* main: (30 commits)
  pythongh-103987: fix several crashes in mmap module (python#103990)
  docs: fix wrong indentation causing rendering error in dis page (python#104661)
  pythongh-94906: Support multiple steps in math.nextafter (python#103881)
  pythongh-104472: Skip `test_subprocess.ProcessTestCase.test_empty_env` if ASAN is enabled (python#104667)
  pythongh-103839: Allow building Tkinter against Tcl 8.7 without external libtommath (pythonGH-103842)
  pythongh-85984: New additions and improvements to the tty library. (python#101832)
  pythongh-104659: Consolidate python examples in enum documentation (python#104665)
  pythongh-92248: Deprecate `type`, `choices`, `metavar` parameters of `argparse.BooleanOptionalAction` (python#103678)
  pythongh-104645: fix error handling in marshal tests (python#104646)
  pythongh-104600: Make type.__type_params__ writable (python#104634)
  pythongh-104602: Add additional test for listcomp with lambda (python#104639)
  pythongh-104640: Disallow walrus in comprehension within type scopes (python#104641)
  pythongh-103921: Rename "type" header in argparse docs (python#104654)
  Improve readability of `typing._ProtocolMeta.__instancecheck__` (python#104649)
  pythongh-96522: Fix deadlock in pty.spawn (python#96639)
  pythonGH-102818: Do not call `PyTraceBack_Here` in sys.settrace trampoline.  (pythonGH-104579)
  pythonGH-103545: Add macOS specific constants for ``os.setpriority`` to ``os`` (python#104606)
  pythongh-104623: Update macOS installer to SQLite 3.42.0 (pythonGH-104624)
  pythongh-104619: never leak comprehension locals to outer locals() (python#104637)
  pythongh-104602: ensure all cellvars are known up front (python#104603)
  ...
@carljm carljm deleted the 709locals branch June 16, 2023 17:39
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PEP 709: Comprehension iteration variable leaks into outer locals()
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