When calling Py_SetPath(), the value that is passed in is ignored.

It's a 3.8 regression: I set the priority to release blocker.

A very simple way to reproduce the bug:

Using pyInstaller, after applying these patches (to fix other Python3.8 issues)

https://github.com/pyinstaller/pyinstaller/pull/4441
https://github.com/pyinstaller/pyinstaller/pull/4440

you will get

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'

This is because Python will use the default value for sys.path, including the "lib" subdirectory:

/dist/hello/lib/python3.8
            ^----------------> This should not be here

Instead, that value should be the one that pyinstaller passes when calling Py_SetPath() here: 

https://github.com/pyinstaller/pyinstaller/blob/develop/bootloader/src/pyi_pythonlib.c#L495

So it should be:

/dist/hello/python3.8

That's a regression that I introduced between Python 3.7 and 3.8 when refactoring _PyCoreConfig/_PyPathConfig code into PyConfig/_PyPathConfig. 

Previously, if Py_SetPath() was called, the specified string was used to fill config->module_search_paths. Now, this string is basically ignored.

PR 16298 fix this regression.

> Fatal Python error: init_fs_encoding: failed to get the Python codec of the filesystem encoding

I created bpo-38236 "Dump the Python path configuration at the first import error" which should ease to debug such issues.

New changeset c422167749f92d4170203e996a2c619c818335ea by Victor Stinner in branch 'master':
bpo-38234: Remove _PyPathConfig.dll_path (GH-16307)
https://github.com/python/cpython/commit/c422167749f92d4170203e996a2c619c818335ea

New changeset e267793aa4101b2771ed0e66aaff5743d23f59af by Victor Stinner in branch 'master':
bpo-38234: Fix PyConfig_Read() when Py_SetPath() was called (GH-16298)
https://github.com/python/cpython/commit/e267793aa4101b2771ed0e66aaff5743d23f59af

New changeset 9f3dcf802eefeb5ab821ce3c7204ab46557d53d7 by Victor Stinner in branch '3.8':
[3.8] bpo-38234: Fix PyConfig_Read() when Py_SetPath() was called (GH-16298) (GH-16313)
https://github.com/python/cpython/commit/9f3dcf802eefeb5ab821ce3c7204ab46557d53d7

> When calling Py_SetPath(), the value that is passed in is ignored.

I fixed this regression. Thanks for the bug report.

Why are we keeping the DLL path around at all? It should only be being used in 1-2 places during path calculation.

Steve:
> Why are we keeping the DLL path around at all? It should only be being used in 1-2 places during path calculation.

_PyPathConfig_Init() initializes _Py_dll_path global variable which is only used by _Py_CheckPython3(). _Py_CheckPython3() is called at each _PyImport_FindSharedFuncptrWindows() call which is used by _PyImport_LoadDynamicModuleWithSpec() (to import a .pyd extension). I tried to minimize my changes to fix the issue, I tried to leave _Py_CheckPython3() unchanged. But I made one change in _Py_CheckPython3(): it handles the case _Py_dll_path=NULL... which should never occur, but I wasn't 100% sure that it really can never occur.

Python 3.6 (before my init work), _Py_CheckPython3() used "static wchar_t dllpath[MAXPATHLEN+1];": it was less important when dllpath is initialized.

--

_PyPathConfig_Calculate() of PC/getpathp.c now uses a temporary variable which stores the result of _Py_GetDLLPath().

> _PyPathConfig_Init() initializes _Py_dll_path global variable which is only used by _Py_CheckPython3().

Ah okay, maybe I'll take the time later on (in a separate issue) to get rid of it fully. We may as well load python3.dll at startup anyway, it's not expensive.

> When calling Py_SetPath(), the value that is passed in is ignored.

Hum, in fact the bug was even worse: Py_SetPythonHome() and Py_SetProgramName() calls are also ignored. I'm not sure when I introduced these regressions.

PR 16335 fix this bug as well.

New changeset 9c42f8cda552694f3b47d6388d4ae84d61731872 by Victor Stinner in branch 'master':
bpo-38234: Fix _PyConfig_InitPathConfig() (GH-16335)
https://github.com/python/cpython/commit/9c42f8cda552694f3b47d6388d4ae84d61731872

New changeset 3f5409a3f13c59baa34656bccefdc3728e46c9ef by Victor Stinner in branch '3.8':
bpo-38234: Fix _PyConfig_InitPathConfig() (GH-16335) (GH-16336)
https://github.com/python/cpython/commit/3f5409a3f13c59baa34656bccefdc3728e46c9ef

New changeset 85ce0a7178801b538160cbb5cf9ef50a713c45bf by Victor Stinner in branch 'master':
bpo-38234: read_pth_file() now returns PyStatus (GH-16338)
https://github.com/python/cpython/commit/85ce0a7178801b538160cbb5cf9ef50a713c45bf

New changeset 7f7cd899e3d773b803b7af5b0c19eeff83dd69fe by Miss Islington (bot) in branch '3.8':
bpo-38234: read_pth_file() now returns PyStatus (GH-16338)
https://github.com/python/cpython/commit/7f7cd899e3d773b803b7af5b0c19eeff83dd69fe

New changeset 1ce152a42eaa917d7763bce93f1e1ca72530d7ca by Victor Stinner in branch 'master':
bpo-38234: Py_SetPath() uses the program full path (GH-16357)
https://github.com/python/cpython/commit/1ce152a42eaa917d7763bce93f1e1ca72530d7ca

New changeset bb6bf7d342b4503a6227fd209fac934905b6a1aa by Victor Stinner in branch 'master':
bpo-38234: Add tests for Python init path config (GH-16358)
https://github.com/python/cpython/commit/bb6bf7d342b4503a6227fd209fac934905b6a1aa

New changeset 52ad33abbfb6637d74932617c7013bae0ccf6e32 by Victor Stinner in branch 'master':
bpo-38234: test_embed: test pyvenv.cfg and pybuilddir.txt (GH-16366)
https://github.com/python/cpython/commit/52ad33abbfb6637d74932617c7013bae0ccf6e32

New changeset 221fd84703c545408bbb4a6e0b58459651331f5c by Victor Stinner in branch 'master':
bpo-38234: Cleanup getpath.c (GH-16367)
https://github.com/python/cpython/commit/221fd84703c545408bbb4a6e0b58459651331f5c

The new tests fail on macOS.

x86-64 High Sierra 3.x:
https://buildbot.python.org/all/#/builders/145/builds/2469

======================================================================
FAIL: test_init_pybuilddir (test.test_embed.InitConfigTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/test/test_embed.py", line 1130, in test_init_pybuilddir
    self.check_all_configs("test_init_compat_config", config,
  File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/test/test_embed.py", line 681, in check_all_configs
    self.check_config(configs, expected_config)
  File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/test/test_embed.py", line 613, in check_config
    self.assertEqual(config, expected)
AssertionError: {'_co[655 chars]ne, 'module_search_paths': ['/Users/buildbot/b[1407 chars]': 1} != {'_co[655 chars]ne, 'executable': '/var/folders/sy/9hwmqyx14s1[1383 chars]': 1}
  {'_config_init': 1,
   '_init_main': 1,
   '_install_importlib': 1,
   'argv': [''],
   'base_exec_prefix': '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target',
-  'base_executable': '/private/var/folders/sy/9hwmqyx14s11577cvgzwf2v40000gt/T/tmp2a98rb5k/_testembed',
?                      --------

+  'base_executable': '/var/folders/sy/9hwmqyx14s11577cvgzwf2v40000gt/T/tmp2a98rb5k/_testembed',
   'base_prefix': '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target',
   'buffered_stdio': 1,
   'bytes_warning': 0,
   'check_hash_pycs_mode': 'default',
   'configure_c_stdio': 0,
   'dev_mode': 0,
   'dump_refs': 0,
   'exec_prefix': '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target',
-  'executable': '/private/var/folders/sy/9hwmqyx14s11577cvgzwf2v40000gt/T/tmp2a98rb5k/_testembed',
?                 --------

+  'executable': '/var/folders/sy/9hwmqyx14s11577cvgzwf2v40000gt/T/tmp2a98rb5k/_testembed',
   'faulthandler': 0,
   'hash_seed': 0,
   'home': None,
   'import_time': 0,
   'inspect': 0,
   'install_signal_handlers': 1,
   'interactive': 0,
   'isolated': 0,
   'malloc_stats': 0,
   'module_search_paths': ['/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target/lib/python39.zip',
                           '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib',
                           '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/build/lib.macosx-10.13-x86_64-3.9-pydebug',
                           '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target/lib/python39.zip',
                           '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target/lib/python3.9',
-                          '/private/var/folders/sy/9hwmqyx14s11577cvgzwf2v40000gt/T/tmp2a98rb5k/libdir'],
?                           --------

+                          '/var/folders/sy/9hwmqyx14s11577cvgzwf2v40000gt/T/tmp2a98rb5k/libdir'],
   'optimization_level': 0,
   'parse_argv': 0,
   'parser_debug': 0,
   'pathconfig_warnings': 1,
   'prefix': '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target',
   'program_name': './_testembed',
   'pycache_prefix': None,
   'pythonpath_env': '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target/lib/python39.zip:/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib:/Users/buildbot/buildarea/3.x.billenstein-sierra/build/build/lib.macosx-10.13-x86_64-3.9-pydebug',
   'quiet': 0,
   'run_command': None,
   'run_filename': None,
   'run_module': None,
   'show_alloc_count': 0,
   'show_ref_count': 0,
   'site_import': 1,
   'skip_source_first_line': 0,
   'tracemalloc': 0,
   'use_environment': 1,
   'use_hash_seed': 0,
   'user_site_directory': 1,
   'verbose': 0,
   'warnoptions': [],
   'write_bytecode': 1,
   'xoptions': []}

======================================================================
FAIL: test_init_pyvenv_cfg (test.test_embed.InitConfigTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/test/test_embed.py", line 1182, in test_init_pyvenv_cfg
    self.check_all_configs("test_init_compat_config", config,
  File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/test/test_embed.py", line 681, in check_all_configs
    self.check_config(configs, expected_config)
  File "/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib/test/test_embed.py", line 613, in check_config
    self.assertEqual(config, expected)
AssertionError: {'_co[655 chars]ne, 'module_search_paths': ['/Users/buildbot/b[1416 chars]': 1} != {'_co[655 chars]ne, 'executable': '/var/folders/sy/9hwmqyx14s1[1400 chars]': 1}
  {'_config_init': 1,
   '_init_main': 1,
   '_install_importlib': 1,
   'argv': [''],
   'base_exec_prefix': '/var/folders/sy/9hwmqyx14s11577cvgzwf2v40000gt/T/tmprrz3csek',
-  'base_executable': '/private/var/folders/sy/9hwmqyx14s11577cvgzwf2v40000gt/T/tmpczgnz4r3/_testembed',
?                      --------

+  'base_executable': '/var/folders/sy/9hwmqyx14s11577cvgzwf2v40000gt/T/tmpczgnz4r3/_testembed',
   'base_prefix': '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target',
   'buffered_stdio': 1,
   'bytes_warning': 0,
   'check_hash_pycs_mode': 'default',
   'configure_c_stdio': 0,
   'dev_mode': 0,
   'dump_refs': 0,
   'exec_prefix': '/var/folders/sy/9hwmqyx14s11577cvgzwf2v40000gt/T/tmprrz3csek',
-  'executable': '/private/var/folders/sy/9hwmqyx14s11577cvgzwf2v40000gt/T/tmpczgnz4r3/_testembed',
?                 --------

+  'executable': '/var/folders/sy/9hwmqyx14s11577cvgzwf2v40000gt/T/tmpczgnz4r3/_testembed',
   'faulthandler': 0,
   'hash_seed': 0,
   'home': None,
   'import_time': 0,
   'inspect': 0,
   'install_signal_handlers': 1,
   'interactive': 0,
   'isolated': 0,
   'malloc_stats': 0,
   'module_search_paths': ['/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target/lib/python39.zip',
                           '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib',
                           '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/build/lib.macosx-10.13-x86_64-3.9-pydebug',
                           '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target/lib/python39.zip',
                           '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target/lib/python3.9',
                           '/var/folders/sy/9hwmqyx14s11577cvgzwf2v40000gt/T/tmprrz3csek/lib/python3.9/lib-dynload'],
   'optimization_level': 0,
   'parse_argv': 0,
   'parser_debug': 0,
   'pathconfig_warnings': 1,
   'prefix': '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target',
   'program_name': './_testembed',
   'pycache_prefix': None,
   'pythonpath_env': '/Users/buildbot/buildarea/3.x.billenstein-sierra/build/target/lib/python39.zip:/Users/buildbot/buildarea/3.x.billenstein-sierra/build/Lib:/Users/buildbot/buildarea/3.x.billenstein-sierra/build/build/lib.macosx-10.13-x86_64-3.9-pydebug',
   'quiet': 0,
   'run_command': None,
   'run_filename': None,
   'run_module': None,
   'show_alloc_count': 0,
   'show_ref_count': 0,
   'site_import': 1,
   'skip_source_first_line': 0,
   'tracemalloc': 0,
   'use_environment': 1,
   'use_hash_seed': 0,
   'user_site_directory': 1,
   'verbose': 0,
   'warnoptions': [],
   'write_bytecode': 1,
   'xoptions': []}

And on FreeBSD.

AMD64 FreeBSD CURRENT Shared 3.x:
https://buildbot.python.org/all/#/builders/168/builds/1510

======================================================================
FAIL: test_init_pybuilddir (test.test_embed.InitConfigTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/test_embed.py", line 1130, in test_init_pybuilddir
    self.check_all_configs("test_init_compat_config", config,
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/test_embed.py", line 681, in check_all_configs
    self.check_config(configs, expected_config)
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/test_embed.py", line 613, in check_config
    self.assertEqual(config, expected)
AssertionError: {'_co[671 chars]ne, 'module_search_paths': ['/usr/home/buildbo[1297 chars]': 1} != {'_co[671 chars]ne, 'executable': '/tmp/tmpsa4mgwz2/_testembed[1285 chars]': 1}
  {'_config_init': 1,
   '_init_main': 1,
   '_install_importlib': 1,
   'argv': [''],
   'base_exec_prefix': '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target',
-  'base_executable': '/var/tmp/tmpsa4mgwz2/_testembed',
?                      ----

+  'base_executable': '/tmp/tmpsa4mgwz2/_testembed',
   'base_prefix': '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target',
   'buffered_stdio': 1,
   'bytes_warning': 0,
   'check_hash_pycs_mode': 'default',
   'configure_c_stdio': 0,
   'dev_mode': 0,
   'dump_refs': 0,
   'exec_prefix': '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target',
-  'executable': '/var/tmp/tmpsa4mgwz2/_testembed',
?                 ----

+  'executable': '/tmp/tmpsa4mgwz2/_testembed',
   'faulthandler': 0,
   'hash_seed': 0,
   'home': None,
   'import_time': 0,
   'inspect': 0,
   'install_signal_handlers': 1,
   'interactive': 0,
   'isolated': 0,
   'malloc_stats': 0,
   'module_search_paths': ['/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target/lib/python39.zip',
                           '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib',
                           '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/build/lib.freebsd-13.0-CURRENT-amd64-3.9-pydebug',
                           '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target/lib/python39.zip',
                           '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target/lib/python3.9',
-                          '/var/tmp/tmpsa4mgwz2/libdir'],
?                           ----

+                          '/tmp/tmpsa4mgwz2/libdir'],
   'optimization_level': 0,
   'parse_argv': 0,
   'parser_debug': 0,
   'pathconfig_warnings': 1,
   'prefix': '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target',
   'program_name': './_testembed',
   'pycache_prefix': None,
   'pythonpath_env': '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target/lib/python39.zip:/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib:/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/build/lib.freebsd-13.0-CURRENT-amd64-3.9-pydebug',
   'quiet': 0,
   'run_command': None,
   'run_filename': None,
   'run_module': None,
   'show_alloc_count': 0,
   'show_ref_count': 0,
   'site_import': 1,
   'skip_source_first_line': 0,
   'tracemalloc': 0,
   'use_environment': 1,
   'use_hash_seed': 0,
   'user_site_directory': 1,
   'verbose': 0,
   'warnoptions': [],
   'write_bytecode': 1,
   'xoptions': []}

======================================================================
FAIL: test_init_pyvenv_cfg (test.test_embed.InitConfigTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/test_embed.py", line 1182, in test_init_pyvenv_cfg
    self.check_all_configs("test_init_compat_config", config,
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/test_embed.py", line 681, in check_all_configs
    self.check_config(configs, expected_config)
  File "/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib/test/test_embed.py", line 613, in check_config
    self.assertEqual(config, expected)
AssertionError: {'_co[671 chars]ne, 'module_search_paths': ['/usr/home/buildbo[1216 chars]': 1} != {'_co[671 chars]ne, 'executable': '/tmp/tmpszvtbyq4/_testembed[1208 chars]': 1}
  {'_config_init': 1,
   '_init_main': 1,
   '_install_importlib': 1,
   'argv': [''],
   'base_exec_prefix': '/tmp/tmpr0gyjdqs',
-  'base_executable': '/var/tmp/tmpszvtbyq4/_testembed',
?                      ----

+  'base_executable': '/tmp/tmpszvtbyq4/_testembed',
   'base_prefix': '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target',
   'buffered_stdio': 1,
   'bytes_warning': 0,
   'check_hash_pycs_mode': 'default',
   'configure_c_stdio': 0,
   'dev_mode': 0,
   'dump_refs': 0,
   'exec_prefix': '/tmp/tmpr0gyjdqs',
-  'executable': '/var/tmp/tmpszvtbyq4/_testembed',
?                 ----

+  'executable': '/tmp/tmpszvtbyq4/_testembed',
   'faulthandler': 0,
   'hash_seed': 0,
   'home': None,
   'import_time': 0,
   'inspect': 0,
   'install_signal_handlers': 1,
   'interactive': 0,
   'isolated': 0,
   'malloc_stats': 0,
   'module_search_paths': ['/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target/lib/python39.zip',
                           '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib',
                           '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/build/lib.freebsd-13.0-CURRENT-amd64-3.9-pydebug',
                           '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target/lib/python39.zip',
                           '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target/lib/python3.9',
                           '/tmp/tmpr0gyjdqs/lib/python3.9/lib-dynload'],
   'optimization_level': 0,
   'parse_argv': 0,
   'parser_debug': 0,
   'pathconfig_warnings': 1,
   'prefix': '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target',
   'program_name': './_testembed',
   'pycache_prefix': None,
   'pythonpath_env': '/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/target/lib/python39.zip:/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/Lib:/usr/home/buildbot/python/3.x.koobs-freebsd-current/build/build/lib.freebsd-13.0-CURRENT-amd64-3.9-pydebug',
   'quiet': 0,
   'run_command': None,
   'run_filename': None,
   'run_module': None,
   'show_alloc_count': 0,
   'show_ref_count': 0,
   'site_import': 1,
   'skip_source_first_line': 0,
   'tracemalloc': 0,
   'use_environment': 1,
   'use_hash_seed': 0,
   'user_site_directory': 1,
   'verbose': 0,
   'warnoptions': [],
   'write_bytecode': 1,
   'xoptions': []}

New changeset 00508a7407d7d300b487532e2271534b20e378a7 by Victor Stinner in branch 'master':
bpo-38234: Fix test_embed pathconfig tests (GH-16390)
https://github.com/python/cpython/commit/00508a7407d7d300b487532e2271534b20e378a7

New changeset 8bf39b606ef7b02c0279a80789f3c4824b0da5e9 by Victor Stinner in branch 'master':
bpo-38234: Add test_init_setpath_config() to test_embed (GH-16402)
https://github.com/python/cpython/commit/8bf39b606ef7b02c0279a80789f3c4824b0da5e9

New changeset 88feaecd46a8f427e30ef7ad8cfcddfe392a2402 by Victor Stinner in branch 'master':
bpo-38234: Complete init config documentation (GH-16404)
https://github.com/python/cpython/commit/88feaecd46a8f427e30ef7ad8cfcddfe392a2402

New changeset 49d99f01e6e51acec5ca57a02e857f0796bc418b by Victor Stinner in branch 'master':
bpo-38234: Fix test_embed.test_init_setpath_config() on FreeBSD (GH-16406)
https://github.com/python/cpython/commit/49d99f01e6e51acec5ca57a02e857f0796bc418b

Oh, there is a regression:

vstinner@apu$ ./python
Python 3.9.0a0 (heads/master:88feaecd46, Sep 26 2019, 03:26:37) 
[GCC 9.2.1 20190827 (Red Hat 9.2.1-1)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import _tkinter
Could not find platform independent libraries <prefix>
Could not find platform dependent libraries <exec_prefix>
Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]

PyInit__tkinter() calls Py_GetProgramName(). But Python initialization no longer copies PyConfig path configuration into _Py_path_info (the global configuration). So Python has to recompute the path configuration which logs 3 warnings.

New changeset 12f2f177fc483723406d7917194e7f655a20631b by Victor Stinner in branch 'master':
bpo-38234: Py_Initialize() sets global path configuration (GH-16421)
https://github.com/python/cpython/commit/12f2f177fc483723406d7917194e7f655a20631b

New changeset 96c8475362acb41decd1d7db9243f328973e5de7 by Victor Stinner in branch '3.8':
[3.8] bpo-38234: Backport init path config changes from master (GH-16423)
https://github.com/python/cpython/commit/96c8475362acb41decd1d7db9243f328973e5de7

> Oh, there is a regression: (...) PyInit__tkinter() calls Py_GetProgramName(). But Python initialization no longer copies PyConfig path configuration into _Py_path_info (the global configuration). So Python has to recompute the path configuration which logs 3 warnings.

It's fixed by commit 12f2f177fc483723406d7917194e7f655a20631b which adds new tests to prevent any regression.

Oh, the main issue has been fixed and I added a lot of tests. So I remove the "release blocker" priority.

I would like to keep the issue open since I plan to do one more change: use PyWideStringList in _PyPathConfig for module_search_paths to support paths which contains DELIM (":" on Unix).

The initial issue has been fixed, I close the issue.

> I would like to keep the issue open since I plan to do one more change: use PyWideStringList in _PyPathConfig for module_search_paths to support paths which contains DELIM (":" on Unix).

I may use bpo-38353 instead for that. See also bpo-31210.