python / python/cpython

3.11 Regression, Py_Initialize; Fatal Python error: init_fs_encoding: failed to get the Python codec of the filesystem encoding

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3.11 OS-windows type-bug
Dominant language
Python
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Avg merge
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Merged PRs (30d)
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Description

Bug report

Build and run the following program;

  #include <Python.h>
  
  int main(int argc, char* argv[])
  {
    Py_Initialize();
    return 0;
  }

The resulting executable runs fine when executed against the installed C:\Program Files\Python311\python311.dll

Executing against python311.dll copied to some other folder (C:\Windows\System32 for instance) results in;

Fatal Python error: init_fs_encoding: failed to get the Python codec of the filesystem encoding
Python runtime state: core initialized
ModuleNotFoundError: No module named 'encodings'

Current thread 0x0000333c (most recent call first):
  <no Python frame>

When also C:\Program Files\Python311\Lib\encodings is copied then the executable runs fine again.

This is not the case with Python versions prior to 3.11. The only thing needed to run Python embedded for versions below 3.11 is the appropriate pythonXXX.dll

Your environment

  • CPython versions tested on:
    Python 3.11.0 (main, Oct 24 2022, 18:26:48) [MSC v.1933 64 bit (AMD64)] on win32
  • Operating system and architecture:
    Edition Windows 11 Pro
    Version 21H2
    Installed on ‎11/‎24/‎2021
    OS build 22000.1098
    Experience Windows Feature Experience Pack 1000.22000.1098.0
  • Compiler used:
    Microsoft Visual Studio Community 2022
    Version 17.3.6
    VisualStudio.17.Release/17.3.6+32929.385
    Microsoft .NET Framework
    Version 4.8.04161
    Installed Version: Community
    Visual C++ 2022 00482-90000-00000-AA258
    Microsoft Visual C++ 2022

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the C program using Py_Initialize and Python.h, reproducing the behavior on Windows 11 with Python 3.11. Compare execution with the installed python311.dll, a copied DLL, and earlier Python versions, then investigate how initialization locates Lib/encodings. Done means the copied Python 3.11 DLL can initialize without separately copying the encodings directory.

Written by the indexing model from the issue text.

Assessment

Tech stack
c, python
Domain
api, operating-systems
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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