riscv64 INTERNAL ERROR unless `--num-workers 1`

[mr-c]

Crash Report

$ # pip install mypy from a fresh git checkout
$ mypy  --config-file mypy_self_check.ini -p mypy
error: INTERNAL ERROR -- Please try using mypy master on GitHub:
https://mypy.readthedocs.io/en/stable/common_issues.html#using-a-development-mypy-build
Please report a bug at https://github.com/python/mypy/issues
version: 2.3.1
note: use --pdb to drop into pdb
Failed to establish connection with worker: No status file found
Failed to establish connection with worker: No status file found
Failed to establish connection with worker: No status file found
Failed to establish connection with worker: No status file found
Traceback (most recent call last):
  File "/home/crusoe/mypy_sid_riscv64/env3.14/bin/mypy", line 6, in <module>
    sys.exit(console_entry())
  File "/home/crusoe/mypy_sid_riscv64/env3.14/lib/python3.14/site-packages/mypy/__main__.py", line 16, in console_entry
    main()
    ~~~~^^
  File "/home/crusoe/mypy_sid_riscv64/env3.14/lib/python3.14/site-packages/mypy/main.py", line 154, in main
    res, messages, blockers = run_build(sources, options, fscache, t0, stdout, stderr)
                              ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/crusoe/mypy_sid_riscv64/env3.14/lib/python3.14/site-packages/mypy/main.py", line 244, in run_build
    res = build.build(sources, options, None, flush_errors, fscache, stdout, stderr)
  File "/home/crusoe/mypy_sid_riscv64/env3.14/lib/python3.14/site-packages/mypy/build.py", line 422, in build
    result = build_inner(
        sources,
    ...<9 lines>...
        metastore,
    )
  File "/home/crusoe/mypy_sid_riscv64/env3.14/lib/python3.14/site-packages/mypy/build.py", line 537, in build_inner
    graph = dispatch(sources, manager, stdout, connect_threads)
  File "/home/crusoe/mypy_sid_riscv64/env3.14/lib/python3.14/site-packages/mypy/build.py", line 4145, in dispatch
    raise OSError(f"Cannot connect to build worker(s): {', '.join(not_connected)}")
OSError: Cannot connect to build worker(s): 0, 1, 2, 3

Traceback

Same as above

To Reproduce

$ git clone https://github.com/python/mypy.git
$ python3.14 -m venv env3.14
$ . env3.14/bin/activate
$ cd mypy
$ python3 -m pip install --upgrade .
$ pip install -r test-requirements.txt
$ mypy  --config-file mypy_self_check.ini -p mypy

Your Environment

• Mypy version used: latest from git, same failure with 2.3.1 and 2.2.0
• Mypy command-line flags:
• Mypy configuration options from mypy.ini (and other config files):
• Python version used: 3.14.7-3
• Operating system and version: Debian "sid" (development version)

[mr-c]

After a successful test using --num-workers 1, (and thus a .mypy_cache directory is populated), a run without --num-workers 1 might get an additional error message (one for each auto-detected CPU core):

$ mypy --show-traceback   --config-file mypy_self_check.ini -p mypy
Traceback (most recent call last):
  File "<frozen runpy>", line 203, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "/home/crusoe/mypy_sid_riscv64/env3.14/lib/python3.14/site-packages/mypy/build_worker/__main__.py", line 6, in <module>
    console_entry()
    ~~~~~~~~~~~~~^^
  File "/home/crusoe/mypy_sid_riscv64/env3.14/lib/python3.14/site-packages/mypy/build_worker/worker.py", line 361, in console_entry
    main(sys.argv[1:])
    ~~~~^^^^^^^^^^^^^^
  File "/home/crusoe/mypy_sid_riscv64/env3.14/lib/python3.14/site-packages/mypy/build_worker/worker.py", line 95, in main
    with open(args.options_data, "rb") as f:
         ~~~~^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '.mypy_cache/.worker_options.44359ce3.data'

[ x4, and then the same error messages as originally reported ]

[mr-c]

  File "/home/crusoe/mypy_sid_riscv64/mypy-git/mypy/nativeparse.py", line 1368, in read_expression                                                                                                                                     
    se.has_surrogates = read_bool(data)                                                                                                                                                                                                
                        ~~~~~~~~~^^^^^^                                                                                                                                                                                                
ValueError: invalid bool value      

hmm.. maybe a librt issue?

[mr-c]

(Pdb) from librt.internal import read_bytes
(Pdb) read_bytes(data)
b':\x14"\xff\x982\x1a\x14B\xff\xab\x14\x1a\x01\xa9'