Incorrect line number calculated in traceback

[pablogsal]

Consider the following code:

def _run_with_file_output():
    example_report_generation_message= (
            """
            """
    ).strip()
    raise ValueError()

_run_with_file_output()

If you execute this with 3.11.0a7 you get (correct traceback):

Traceback (most recent call last):
  File "/home/pablogsal/github/python/3.11/lel.py", line 8, in <module>
    _run_with_file_output()
    ^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/pablogsal/github/python/3.11/lel.py", line 6, in _run_with_file_output
    raise ValueError()
    ^^^^^^^^^^^^^^^^^^
ValueError

but on 3.11.0b1 you get:

Traceback (most recent call last):
  File "/home/pablogsal/github/python/3.11/lel.py", line 8, in <module>
    _run_with_file_output()
    ^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/pablogsal/github/python/3.11/lel.py", line 255, in _run_with_file_output
ValueError

Notice that the last line number for _run_with_file_output is wrong (255 instead of 6).

Bisecting points at:

944fffee8916cb94321fa33cd3a43f4108717746 is the first bad commit
commit 944fffee8916cb94321fa33cd3a43f4108717746
Author: Mark Shannon <mark@hotpy.org>
Date:   Thu Apr 21 16:10:37 2022 +0100

    GH-88116: Use a compact format to represent end line and column offsets. (GH-91666)

    * Stores all location info in linetable to conform to PEP 626.

    * Remove column table from code objects.

    * Remove end-line table from code objects.

    * Document new location table format

[pablogsal]

Originally noticed by @godlygeek

[pablogsal]

Notice that if you change the input to be:

def _run_with_file_output():
    _= (
            """
            """
    ).strip()
    raise ValueError()

_run_with_file_output()

Then the line numbers and the tracebacks are correct (likely due to the difference in column offset):

Traceback (most recent call last):
  File "/home/pablogsal/github/python/3.11/lel.py", line 8, in <module>
    _run_with_file_output()
    ^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/pablogsal/github/python/3.11/lel.py", line 6, in _run_with_file_output
    raise ValueError()
    ^^^^^^^^^^^^^^^^^^
ValueError

[pablogsal]

May be related to #93249

[markshannon]

It looks like the table is correct, but the parsing to get the line number is wrong.
.__code__.co_positions() shows the correct positions, but .__code__.co_lines() shows the wrong line numbers.

[markshannon]

It's actually a bug in compiler front-end. It produces an instruction with lineno == end_lineno but end_col_offset < col_offset

[markshannon]

#93673

[iritkatriel]

Backport to 3.11: #93895