How to add python-blosc2 to PyInstaller's spec file?

[ShootingStarDragon]

My googling and chatgpt skills have failed me. I have a simple test importing blosc and after clicking on bloscdir.exe all it does it loop at the beginning (spamming why is blosc2 failing? BEFORE), I suspect that importing blosc to the spec file is incorrect.

test code:
blosctest3.py

try:
    import time
    print("why is blosc2 failing? BEFORE")
    import blosc2
    print("why is blosc2 failing? AFTER")
    time.sleep(1000)
except Exception as e:
    print("blosc died died!", e, flush=True)
    import traceback
    print("full exception", "".join(traceback.format_exception(*sys.exc_info())))

spec for pyinstaller (version ^5.9.0 as per pyproject.toml):
bloscdir.spec

# -*- mode: python ; coding: utf-8 -*-


block_cipher = None

a = Analysis(
    ['blosctest3.py'],
    pathex=[],
    binaries=[],
    datas=[],
    hiddenimports=['blosc2'],
    hookspath=[],
    hooksconfig={},
    runtime_hooks=[],
    excludes=[],
    win_no_prefer_redirects=False,
    win_private_assemblies=False,
    cipher=block_cipher,
    noarchive=False,
)
pyz = PYZ(a.pure, a.zipped_data, cipher=block_cipher)

exe = EXE(
    pyz,
    a.scripts,
    [],
    exclude_binaries=True,
    name='bloscdir',
    debug=False,
    bootloader_ignore_signals=False,
    strip=False,
    upx=True,
    console=True,
    disable_windowed_traceback=False,
    argv_emulation=False,
    target_arch=None,
    codesign_identity=None,
    entitlements_file=None,
)
coll = COLLECT(
    exe,
    a.binaries,
    a.zipfiles,
    a.datas,
    strip=False,
    upx=True,
    upx_exclude=[],
    name='bloscdir',
)

to build the onedir: python -m PyInstaller bloscdir.spec --clean

I suspect it has something to do with either blosc's __init__ not working right or not bundling the assorted .h files in the include folder of the environment, like b2nd.h, blosc2.h, and the blosc2 folder.

more info:
windows 10
python: 3.9.0

[ShootingStarDragon]

As usual, after the moment I post I find the answer: call multiprocessing.freeze_support before importing blosc.
pyinstaller/pyinstaller#7470 (comment)

this works:

try:
    # Must be done before importing blosc2
    import multiprocessing
    if __name__ == "__main__":
        multiprocessing.freeze_support()
        import time
        print("why is blosc2 failing? BEFORE, freeze supp")
        import blosc2
        print("why is blosc2 failing? AFTER")
        time.sleep(1000)
except Exception as e:
    print("blosc died died!", e, flush=True)
    import traceback
    print("full exception", "".join(traceback.format_exception(*sys.exc_info())))

Hope this helps someone in the future.