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GeezerVison is showing github.com — GH-103488: Use return-offset, not yield-offset. by markshannon · Pull Request #103502 · python/cpython

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@markshannon

@markshannon markshannon commented Apr 13, 2023 •
edited by bedevere-bot
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This ensures that the callers instruction pointer is correct when sending to a generator or coroutine.

This is necessary for exception handling, and nice for debuggers and profilers.

Instead of returning to prev_instr +1 and yielding to prev_instr - yield_offset + 1 we now return to prev_instr + return_offset + 1 and yield to prev_instr +1.
These are equivalent unless there is an exception, or when introspecting the stack.

Since call/returns are more common than send/yields this will be a tiny bit slower than main, but reverting to the 3.11 approach would a lot slower.
Compared to the 3.11, this makes call/returns a few percent slower and send/yields an order of magnitude faster.

  • Issue: Python 3.12.0a7 can fail to catch exceptions when an iterator is involved #103488

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markshannon added 4 commits April 12, 2023 19:23
@markshannon
Use return-offset, not yield-offset, so that instruction pointer is c…
dc9fee6 
…orrect when sending to a generator or coroutine.
@markshannon
Set return_offset on call, instead of resetting it on return.
c86c721
@markshannon
Add news
b4afef3
@markshannon
Add explanatory comment for return_offset.
18fad80
@markshannon
markshannon marked this pull request as ready for review April 13, 2023 10:33
@bedevere-bot bedevere-bot mentioned this pull request Apr 13, 2023
Python 3.12.0a7 can fail to catch exceptions when an iterator is involved #103488
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@bedevere-bot bedevere-bot added the awaiting core review label Apr 13, 2023
iritkatriel
iritkatriel reviewed Apr 13, 2023
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Comment thread Python/bytecodes.c
STACK_SHRINK(shrink_stack);
new_frame->localsplus[0] = owner;
JUMPBY(INLINE_CACHE_ENTRIES_LOAD_ATTR);
frame->return_offset = 0;

@iritkatriel iritkatriel Apr 13, 2023

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What are the rules about when this needs to be 0ed and when it doesn't?

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@markshannon markshannon Apr 13, 2023

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return_offset is only meaningful to the callee, so it needs to be set in any CALL (to a Python function) or SEND (to a coroutine or generator).
If there is no callee, then it is meaningless.

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@markshannon markshannon Apr 13, 2023

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I've added a comment in pycore_frame.h

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@Eclips4

Eclips4 commented Apr 13, 2023

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Also, this PR fixes #101914, output from pylint using example:

(venv) eclips4@HOME-PC:~/ide/cpython$ pylint test.py
************* Module test
test.py:1:0: C0114: Missing module docstring (missing-module-docstring)
test.py:1:4: E0602: Undefined variable 'b' (undefined-variable)
test.py:2:0: E0602: Undefined variable 'func' (undefined-variable)

------------------------------------------------------------------
Your code has been rated at 0.00/10 (previous run: 0.00/10, +0.00)

@mdboom can you confirm that? =)
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iritkatriel
iritkatriel approved these changes Apr 13, 2023
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@bedevere-bot bedevere-bot added awaiting merge and removed awaiting core review labels Apr 13, 2023
@markshannon
markshannon merged commit efb8a25 into python:main Apr 13, 2023
@bedevere-bot bedevere-bot removed the awaiting merge label Apr 13, 2023
carljm added a commit to carljm/cpython that referenced this pull request Apr 13, 2023
@carljm
Merge branch 'main' into superopt
9384106 
* main:
  pythongh-103479: [Enum] require __new__ to be considered a data type (pythonGH-103495)
  pythongh-103365: [Enum] STRICT boundary corrections (pythonGH-103494)
  pythonGH-103488: Use return-offset, not yield-offset. (pythonGH-103502)
  pythongh-103088: Fix test_venv error message to avoid bytes/str warning (pythonGH-103500)
  pythonGH-103082: Turn on branch events for FOR_ITER instructions. (python#103507)
  pythongh-102978: Fix mock.patch function signatures for class and staticmethod decorators (python#103228)
  pythongh-103462: Ensure SelectorSocketTransport.writelines registers a writer when data is still pending (python#103463)
  pythongh-95299: Rework test_cppext.py to not invoke setup.py directly (python#103316)
@mdboom mdboom mentioned this pull request Apr 20, 2023
pylint is broken with CPython main #101914
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@mdboom

mdboom commented Apr 20, 2023

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@mdboom can you confirm that? =)

Yes, confirmed. I closed #101914 as a result.
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@jacobtylerwalls jacobtylerwalls mentioned this pull request May 18, 2023
crash caused by unimplemented code feature pylint-dev/pylint#8695
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@markshannon
markshannon deleted the fix-103488 branch September 26, 2023 12:55
@cdce8p cdce8p mentioned this pull request Feb 20, 2024
Python 3.12 - ValueError: generator already executing pylint-dev/pylint#9138
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@iritkatriel iritkatriel iritkatriel approved these changes

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@markshannon @Eclips4 @mdboom @iritkatriel @bedevere-bot
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