build not running on windows

[eventcatcher]

I have a strange behaviour on Windows. I have tested this on a VM with Windows 11 ARM, and a PC with Windows 10 (x86 64bit).

My requirements.txt:
requests==2.32.3
chardet==5.2.0
python-dateutil
pyweatherbit
feedparser
unidecode
urllib3
sdnotify
rich
freetype-py
PyJWT
cryptography
roonapi
spotipy
pillow
pyweatherbit
certifi
websockets==13.1
platformdirs

• started app in VScode (Runa and Debug) it works, serious-python has loaded all packages and the Python script is running fine.

• started with 'fvm flutter run --release' it works too.

• build with 'fvm flutter build windows' is well done without errors,

The exe is running, but the Python part is NOT running.

I've got an error in the ntdll.dll, Version: 10.0.26100.8457

module name: ntdll.dll, Version: 10.0.26100.8457, timestamp: 0xac224bdc
Error code: 0xc0000005
Error offset: 0x0000000000193118
process ID:: 0xE44
application path: C:\Users\swilhelm\dev\gits\roonmatrix\build\windows\x64\runner\Release\roonmatrix.exe
module path: C:\WINDOWS\SYSTEM32\ntdll.dll
report ID: ae260409-ecd4-4c49-8149-bbdaa435f64f

Signature:
P1: roonmatrix.exe
P2: 1.2.3.91
P3: 6a0fffb5
P4: ntdll.dll
P5: 10.0.26100.8457
P6: ac224bdc
P7: c0000005
P8: 0000000000193118
P9:
P10:

The error is exactly the same on VM with Win11 and PC with Win10.

The same app on Ubuntu and macOS is running fine.

Do you have any idea what's going on there?
Do you need more information?

[eventcatcher]

Another thing is interesting: it will start successfully if started by Visual Studio (drag exe file to main window and click green play button below the menu bar), but if started directly it will not start the python script!

[FeodorFitsner]

Hi! That ntdll.dll crash with code 0xc0000005 at offset 0x193118 is almost always a DLL-load failure deep inside Windows' loader (LdrpInitializeNode) — i.e. Windows can't resolve a native dependency of one of the Python extension modules in your bundle.

The reason it works under VSCode / flutter run / Visual Studio but not from a double-clicked .exe is that those launchers inherit a much richer PATH (Flutter SDK, your dev Python, VC++ redist paths, etc.) that a standalone exe doesn't see.

Looking at your requirements.txt, the likely culprits are the packages that ship compiled .pyd files with their own native DLL deps:

• cryptography — bundles OpenSSL DLLs; by far the most common cause of this exact crash
• pillow — needs libjpeg / libpng / libtiff
• freetype-py — needs freetype.dll

Things to try / info that would help

1. Run from a terminal, not by double-clicking:

   cd build\windows\x64\runner\Release
   roonmatrix.exe
   

   Python's import error usually prints to stderr just before the crash.

2. Enable verbose imports so we can see which module is the last one Python tries to load:

   set PYTHONVERBOSE=1
   roonmatrix.exe
   

3. Install the latest Microsoft Visual C++ Redistributable (x64) on the target machine — many compiled wheels require it and it's not installed by default on clean Windows.

4. Isolate the bad package: temporarily remove cryptography (and anything that pulls it in — PyJWT[crypto], roonapi, spotipy may) from requirements.txt, rebuild, and see if the app starts. If it does, we know it's OpenSSL DLL resolution inside the bundled package.

5. Check the path length — Windows still has a 260-char MAX_PATH limit unless long-path support is enabled. The unpacked bundle path can get long (build\windows\x64\runner\Release\data\flutter_assets\...). Try building from a shorter path like C:\dev\roonmatrix.

Could you share the output of step 1 or 2? That should pinpoint which import is blowing up.

[eventcatcher]

It works now. The problem was that an old version of the python script was loaded.
From this path: C:\Users\your-username-here\AppData\Roaming\de.eventcatcher\roonmatrix\flet\assets\backend
When the Flutter app is rebuilt, this directory is not deleted, so it is reused each time (like a cache dir).

Maybe the other problem in the script was with output to sys.stdout and/or sys.stderr which is maybe not working on windows.
I'll try to investigate tomorrow if this is the case.

[FeodorFitsner]

Right, sure. Interesting though, flet build windows should not produce exe unpacking anything to AppData dir - everything should be run from app dir directly...