MemoryError in `coverage report` on Python 3.12

[cvzi]

Describe the bug
On Python 3.12 an error occurs in coverage report, lower Python versions seem to be fine:

C:\Users\cuzi\Desktop\coverage_large_dict>coverage report
MemoryError

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "C:\Python312\Scripts\coverage.exe\__main__.py", line 7, in <module>
  File "C:\Python312\Lib\site-packages\coverage\cmdline.py", line 970, in main
    status = CoverageScript().command_line(argv)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python312\Lib\site-packages\coverage\cmdline.py", line 708, in command_line
    total = self.coverage.report(
            ^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python312\Lib\site-packages\coverage\control.py", line 1084, in report
    return reporter.report(morfs, outfile=file)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python312\Lib\site-packages\coverage\report.py", line 181, in report
    for fr, analysis in get_analysis_to_report(self.coverage, morfs):
  File "C:\Python312\Lib\site-packages\coverage\report_core.py", line 100, in get_analysis_to_report
    analysis = coverage._analyze(morf)
               ^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python312\Lib\site-packages\coverage\control.py", line 942, in _analyze
    return analysis_from_file_reporter(data, self.config.precision, file_reporter, filename)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python312\Lib\site-packages\coverage\results.py", line 31, in analysis_from_file_reporter
    statements = file_reporter.lines()
                 ^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python312\Lib\site-packages\coverage\python.py", line 194, in lines
    return self.parser.statements
           ^^^^^^^^^^^
  File "C:\Python312\Lib\site-packages\coverage\python.py", line 189, in parser
    self._parser.parse_source()
  File "C:\Python312\Lib\site-packages\coverage\parser.py", line 271, in parse_source
    self._raw_parse()
  File "C:\Python312\Lib\site-packages\coverage\parser.py", line 154, in _raw_parse
    tokgen = generate_tokens(self.text)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python312\Lib\site-packages\coverage\phystokens.py", line 179, in generate_tokens
    return list(tokenize.generate_tokens(readline))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python312\Lib\tokenize.py", line 577, in _generate_tokens_from_c_tokenizer
    yield TokenInfo._make(info)
          ^^^^^^^^^^^^^^^^^^^^^
  File "C:\Python312\Lib\collections\__init__.py", line 449, in _make
    result = tuple_new(cls, iterable)
             ^^^^^^^^^^^^^^^^^^^^^^^^
SystemError: <built-in method __new__ of type object at 0x00007FFFB9EE6270> returned a result with an exception set

CI logs: https://github.com/cvzi/coverage_large_dict/actions/runs/9125997761/job/25093333034

To Reproduce

• Python 3.12 on Windows and Ubuntu

• coverage.py 7.5.1 with C extension

• coverage debug sys

  -- sys -------------------------------------------------------
                 coverage_version: 7.5.1
                  coverage_module: C:\Python312\Lib\site-packages\coverage\__init__.py
                             core: -none-
                          CTracer: available
             plugins.file_tracers: -none-
              plugins.configurers: -none-
        plugins.context_switchers: -none-
                configs_attempted: C:\Users\cuzi\Desktop\coverage_large_dict\.coveragerc
                                   C:\Users\cuzi\Desktop\coverage_large_dict\setup.cfg
                                   C:\Users\cuzi\Desktop\coverage_large_dict\tox.ini
                                   C:\Users\cuzi\Desktop\coverage_large_dict\pyproject.toml
                     configs_read: C:\Users\cuzi\Desktop\coverage_large_dict\pyproject.toml
                      config_file: None
                  config_contents: -none-
                        data_file: -none-
                           python: 3.12.3 (tags/v3.12.3:f6650f9, Apr  9 2024, 14:05:25) [MSC v.1938 64 bit (AMD64)]
                         platform: Windows-11-10.0.22621-SP0
                   implementation: CPython
                       executable: C:\Python312\python.exe
                     def_encoding: utf-8
                      fs_encoding: utf-8
                              pid: 4188
                              cwd: C:\Users\cuzi\Desktop\coverage_large_dict
                             path: C:\Python312\Scripts\coverage.exe
                                   C:\Python312\python312.zip
                                   C:\Python312\DLLs
                                   C:\Python312\Lib
                                   C:\Python312
                                   C:\Python312\Lib\site-packages
                      environment: COVERAGE_CORE = sysmon
                                   TEMP = C:\Users\cuzi\AppData\Local\Temp
                                   TMP = C:\Users\cuzi\AppData\Local\Temp
                     command_line: C:\Python312\Scripts\coverage debug sys
           sqlite3_sqlite_version: 3.45.1
               sqlite3_temp_store: 0
          sqlite3_compile_options: ATOMIC_INTRINSICS=0, COMPILER=msvc-1938, DEFAULT_AUTOVACUUM,
                                   DEFAULT_CACHE_SIZE=-2000, DEFAULT_FILE_FORMAT=4,
                                   DEFAULT_JOURNAL_SIZE_LIMIT=-1, DEFAULT_MMAP_SIZE=0, DEFAULT_PAGE_SIZE=4096,
                                   DEFAULT_PCACHE_INITSZ=20, DEFAULT_RECURSIVE_TRIGGERS,
                                   DEFAULT_SECTOR_SIZE=4096, DEFAULT_SYNCHRONOUS=2,
                                   DEFAULT_WAL_AUTOCHECKPOINT=1000, DEFAULT_WAL_SYNCHRONOUS=2,
                                   DEFAULT_WORKER_THREADS=0, DIRECT_OVERFLOW_READ, ENABLE_FTS3, ENABLE_FTS4,
                                   ENABLE_FTS5, ENABLE_MATH_FUNCTIONS, ENABLE_RTREE, MALLOC_SOFT_LIMIT=1024,
                                   MAX_ATTACHED=10, MAX_COLUMN=2000, MAX_COMPOUND_SELECT=500,
                                   MAX_DEFAULT_PAGE_SIZE=8192, MAX_EXPR_DEPTH=1000, MAX_FUNCTION_ARG=127,
                                   MAX_LENGTH=1000000000, MAX_LIKE_PATTERN_LENGTH=50000,
                                   MAX_MMAP_SIZE=0x7fff0000, MAX_PAGE_COUNT=0xfffffffe, MAX_PAGE_SIZE=65536,
                                   MAX_SQL_LENGTH=1000000000, MAX_TRIGGER_DEPTH=1000,
                                   MAX_VARIABLE_NUMBER=32766, MAX_VDBE_OP=250000000, MAX_WORKER_THREADS=8,
                                   MUTEX_W32, OMIT_AUTOINIT, SYSTEM_MALLOC, TEMP_STORE=1, THREADSAFE=1
  
  

• What versions of what packages do you have installed? Only coverage and pytest 8.2.0

• What code shows the problem? I suspect it's the large dictionary as a literal in a single line that causes the problem. Something like this:

  a_large_dict_literal = {'\U0001F947':{'en':':1st_place_medal:','status':2,'E':3,'de':':goldmedaille:','es':':medalla_de_oro:','fr':':médaille_d’or:','ja':':金メダル:','ko':':금메달:','pt':':medalha_de_ouro:','it':':medaglia_d’oro:','fa':':مدال_طلا:','id':':medali_emas:','zh':':金牌:','ru':':золотая_медаль:','tr':':birincilik_madalyası:','ar':':ميدالية_مركز_أول:'},'\U0001F948':{'en':':2nd_place_medal:','status':2,'E':3,'de':':silbermedaille:','es':':medalla_de_plata:','fr':':médaille_d’argent:','ja':':銀メダル:','ko':':은메달:','pt':':medalha_de_prata:','it':':medaglia_d’argento:','fa':':مدال_نقره:','id':':medali_perak:','zh':':银牌:','ru':':серебряная_медаль:','tr':':ikincilik_madalyası:','ar':':ميدالية_مركز_ثان:'}, ...

  See this 3 MB file: https://github.com/cvzi/coverage_large_dict/blob/main/largedict/__init__.py

• What commands should we run to reproduce the problem?
  This repository is a minimal example: https://github.com/cvzi/coverage_large_dict

  git clone https://github.com/cvzi/coverage_large_dict.git
  cd coverage_large_dict
  pip install pytest coverage
  coverage run -m pytest
  coverage report
  

Additional context

When the same large dictionary is formated in a pretty way with newlines and spaces, the problem doesn't occur

[devdanzin]

Confirmed: it didn't raise a MemoryError but consumed 19GB of RAM before I killed it.

[devdanzin]

This can be reproduced by converting the large dict to a string, then running:

import io, tokenize
import largedict

text = largedict.d  # The large dict as a string
readline = io.StringIO(text).readline
list(tokenize.generate_tokens(readline))

The excessive memory usage comes from the huge list that is created here:

coveragepy/coverage/phystokens.py

Line 179 in 81089de

return list(tokenize.generate_tokens(readline))

Given that the list is only used to iterate tokens, it might be better to simply return tokenize.generate_tokens(readline).

[nedbat]

Hmm, I don't get it. You say:

The excessive memory usage comes from the huge list that is created here:
return list(tokenize.generate_tokens(readline))

But reformatting the file to be on multiple lines makes it work fine, with a list of 450050 tokens. So it's not just the number of tokens, there's something about the one-line that is the problem, and it's internal to tokenize?

[devdanzin]

So it's not just the number of tokens, there's something about the one-line that is the problem, and it's internal to tokenize?

You're right, I confirmed that removing the list from coverage would reduce the memory usage, but didn't think it through.

When calling list(tokenize.generate_tokens(readline)), memory blows out with a large single line dict, while the same dict broken into lines doesn't cause memory issues. Adding this information to the CPython issue.

[nedbat]

Looks like python/cpython#119118 is narrowing down to a fix, so I'll close this.